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PROCEEDINGS

of the ENTOMOLOGICAL

SOCIETY OF ONTARIO

Voleas Ox why aiedebel, canted is)

L979

Published September, 1980

EDITORS W. E. Heming and C. R. Ellis (Editor Designate), Environmental Biology, University of Guelph, Guelph

EDITORIAL COMMITTEE D. W. Barr, Royal Ontario Museum, Toronto C. R. Ellis, Environmental Biology, University of Guelph, Guelph J. D. Shorthouse, Biology, Laurentian University, Sudbury K. R. Solomon, Environmental Biology, University of Guelph, Guelph

i

Proceedings of the Entomological Society of Ontario Volume 110, 1979

ENTOMOLOGICAL SOCIETY OF ONTARIO

OFFICERS

1979 - 1979 President: D. H. C. HERNE, Vineland Station Vice President: P. E. MORRISON, Waterloo. Past President: E. A. C. HAGLEY, Vineland Station Directors: K. G. DAVEY, Toronto

W. H. FOOTT, Harrow

K. J. GRIFFITHS, Sault Ste. Marie A. HIKICHI, Simcoe

G. B. KINOSHITA, Willowdale

J. E. LAING, Guelph

Secretary: M. V. SMITH, Guelph

Treasurer: D. H. PENGELLY, Guelph

Editors: W. E. HEMING and C. R. ELLIS (Editor Designate), Guelph Librarian: M. K. SEARS, Guelph

Correspondence about membership in the Society or exchange of publications should be addressed to the treasurer, Environmental Biology, University of Guelph, Guelph, Ontario.

il

Proceedings of the Entomological Society of Ontario Volume 110, 1979

CONTENTS

I. THE SOCIETY

eect Par TO) ca Ee ee eee ey Ne mane ten. PNPME SBN Hol 8 stun ee tee, SWS Se ack ded Sal lecdes sab dcede’s RES ETT S LER eel (OF Dt tain So iy Bate ah 9 Re Be OS SRCHMELE MUM OMING HILGSEAS) EGIL Olan es. crere.sesecece ee sseese ceo ote sa ce cne des dy stateen eves castes duvevsaueseous sedatewaseubindoases

Maem Cella NCUITES AS Mn ASUTED ic scrcteze recat cece see ce eencecoes secon s vidceesicconesepecevsacanessécasescccawsstece

Il. SUBMITTED PAPERS

Surgeoner—Evidence of ovicidal activity by fumigant action using chlorpyrifos for con- trol of Haematopinus suis (Anoplura: Haematopinidae) .................::0sssseeeeeseeeeeeeeeeneeees

Barlow and Surgeoner—The efficacy of self-applicating devices for control of the face fly, Musca autumnalis (Diptera: Muscidae) and the horn fly, Haematobia irritans (Diptera: Muscidae) on cattle near Guelph, Ontario ...............ccccccssseececeneceeeceeceeeceeseeees

Elliott and Kemp—Flight activity of the green peach aphid (Homoptera: Aphididae) dur- ing the vegetable growing season at Harrow and Jordan, Ontario ...............:000ssseesseeeeee

Madder and Surgeoner—Effect of permethrin, cypermethrin and chlorpyrifos on louse POGUE ACONS MO fea DEe ICAL Cente rece cc es occ fon seca ee area es Norated cee Siaica si coeccecewse ce sasaccuccesstaeausescueesons

Harcourt et al.—Distribution of Microctonus aethiopoides, a parasitoid of the alfalfa ween Coleoptera: nCunculiomidae)! InVOMtATIO ss... .cc0c.s0.+-eeccecoecascssecesectecosssssvesses<cebenaceousee

Ellis and Roy—The potato leafhopper, Empoasca fabae, (Homoptera: Cicadellidae) and OMSL SES IO fesPe ATLUCS) MMs OMUATI Os seecexs aeosnor< cccssessececscocss caccoccarscecasatsstsscacess+nccdocesessécasenee

Huber and Pengelly—Two new species of Elampus (Hymenoptera: Chrysididae) from Puerto Rico and Cuba with notes on Elampus viridis CressOm ...........:::ccccccsssssssseeeseees

Trottier and Herne—Temperature relationships to forecast hatching of overwintered eggs of the European red mite, Panonychus ulmi (Acarina: Tetranychidae) ................

Foott et al.—tInfestation of Macrosiphum avenae and Rhopalosiphum padi (Homoptera: Apnididae) on winter wheat in Essex’ County, Omtario. :..<:..2.s.co..0.2<.-ccccosoossesssseceesovescces

Tyler and Ellis—Ground beetles in three tillage plots in Ontario and observations on their importance as predators of the northern corn rootworm, Diabrotica longicornis ME BIC O Pleas © MGVSOME IG AC) meceetec tra cersesecen eases tc les seven cece savas dace eeeuscceeuesesecscaccddssesonseoesseoee

Guppy—A comparison of development and fecundity in North American and European populations of the cereal leaf beetle, Oulema melanopus (Coleoptera: Chrysomelidae)

Helson et al.—Susceptibility of Culex spp. and Aedes spp. larvae (Diptera: Culicidae) to fEMepPhosrandChlOnpyMLOs imeSOUtMerm OMbaTiOs .ccessrseeccess-s-cee-c-2-seecceq sce ++occccceeesseseccenecerss

Smith—Population changes of the northern corn rootworm (Coleoptera: Chrysomelidae) anducomuyield losses) im) sOutmwesteGm OMtaniO, s21..c..c.-0-------------ococesteccuccacovsvevssssecccserscences

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19

29

35

41

47

53

61

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85

Proceedings of the Entomological Society of Ontario Volume 110, 1979

Morris—Microbial isolations from Sitophilus zeamais (Coleoptera: Curculionidae) .......... 93

Wilson—Effects of Nosema disstriae (Microsporida) on the forest tent caterpillar, Malacosoma‘disstrias(cepidoptera: Easiocampid ae) es ee 97

Broadbent and Tomlin—Species list of acari recovered from soil of a Guelph cornfield

anda London) pasture ic sci.cec shee ok ole Soscacscccaeiscvasovsdeces con snsesuewoeeceeeee seen ote e eee aCe eee 101 Iii. NOTES Fogal and Kwain—Total protein and amino acid content of the gut of Neodiprion sertifer (Hymenoptera: Diprionidae) during metamorphosis ................---ssseecceeceeeeeeeeers 104 Morris—An attempt to produce aposymbiotic Sitophilus zeamais (Coleoptera: Curculi- onidae) by rearing at33°C | .csc.c.cc.ccdereeea cee eee eee oo renee asa Sek sae Su CS ene ES reese 107 Urquhart—Conservation areas for the eastern population of the monarch butterfly, Danaus plexippus plexippus, (Lepidoptera: Danaidae)) .........-.2....cc.:..:--ssesesseecessueteoneens 109 IV. INDEX 2h oe oo Ee eee pe 110

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Proceedings of the Entomological Society of Ontario Volume 110, 1979

I. THE SOCIETY

RECENT DEATH

KEENAN, W.N. died at Ottawa, Ontario on 11 March 1980 at age 88. He was a former director of Plant Protection Division, Agriculture Canada, an honorary member of the Entomological Society of Canada and a former member of the Entomological Society of Ontario.

PRESIDENT’S PRIZE — 1979

Jon Houseman, Department of Biology, Queen’s University, won this year’s “President’s Prize” for the best student paper presented at the annual meeting in November at the Parkway Inn, St. Catharines, Ontario. His paper entitled “Pro- teinase Activity in the Posterior Midgut of Rhodnius prolixus Stal. (Hemiptera: Reduviidae)”, was judged the best of eight in the competition.

Mr. Houseman was born in Montreal, Quebec and moved to Ontario in 1970. He received a B.Sc. Honours in Biology in 1976 from Queen’s University and a M.Sc. in Entomology from the University of Alberta in 1978. He returned to Queen’s in 1979 for graduate study under the joint supervision of Dr. A. E. R. Downe and Dr. G. R. Wyatt. The objectives of his research were: 1) to identify the digestive proteinases in Rhodnius prolixus, 2) to determine whether the pro- teinases found in this species are similar to those found in other blood feeding Hemipteran insects and, 3) to determine the factors controlling the production of digestive proteinases in R. prolixus.

This is the second award for Mr. Houseman this year. He was awarded a 1979 Ontario Graduate Scholarship and was recently awarded a National Sciences and Engineering Research Council Post Graduate Scholarship for 1980.

TED HEMING RETIRES AS EDITOR

After retirement from the University of Guelph in 1969, Ted Heming served as editor of the Proceedings from 1972-1977 and assistant editor in 1978 and 1979. He recently resigned his position and is in the process of moving to Burlington, Ontario. The executive and members of the Entomological Society of Ontario thank him for his most worthy service and wish him a successful second retirement.

Proceedings of the Entomological Society of Ontario Volume 110, 1979

DAVE PENGELLY RETIRES AS TREASURER

After 16 years of dedicated service, Pro- fessor Dave Pengelly retired from his position as treasurer of the Entomological Society of Ontario. Dave became a director of the Society in 1963-64 and then succeeded C. C. Steward as Secretary-Treasurer in 1964. This position was divided in 1976 and Dave continued as treasurer until 1979. He has spent many hours over the years at the sometimes thankless job of serving the society. He is one of the few remaining historians of the Society and has kept files and letters of some of our early members.

Dave obtained his Ph.D. from Cornell in 1955 and joined the Department of Entom- ology at the University of Guelph the same

. : year. Research with graduate students has in- cluded work on dermestids, simuliids and dytiscids. However, his main interest is Hymenoptera, particularly the ecology and taxonomy of the Apoidea. Whatever the need, Dave always has time for the Society, students and colleagues. His genuine enthusiasm and encouragement in all areas of entomology has inspired many of his students to continue in research. In 1978, he won the exclusive “Alumni Distinguished Teaching Award” presented by the Ontario Agricultural College. The Society thanks Dave for his outstanding contribution of time and effort.

Proceedings of the Entomological Society of Ontario Volume 110, 1979

Il. SUBMITTED PAPERS

EVIDENCE OF OVICIDAL ACTIVITY BY FUMIGANT ACTION USING CHLORPYRIFOS FOR CONTROL OF HAEMATOPINUS SUIS (ANOPLURA: HAEMATOPINIDAE)

G. A. SURGEONER

Department of Environmental Biology, University of Guelph, Guelph, Ontario N1G 2W1

Abstract Proc. ent. Soc. Ont. 110: 3-7 (1979)

In studies evaluating chlorpyrifos, Dursbane® 44, as a spot-on treatment for con- trol of hog lice, Haematopinus suis (L.), 100% reductions were observed at dosages of ca. 10, 20 and 30 mg/kg. Similar reductions were observed on un- treated animals, housed in the same barn, without physical contact with the treated animals. Eggs of lice on treated animals failed to hatch. Evidence is presented that suggests that the louse mortality resulted from a fumigant action.

Introduction

For control of lice with most presently registered insecticides, heavily infested animals should be retreated after 10-14 days. These materials, although effective against the adults and nymphs, do not kill eggs of lice attached to the hairs. After initial treatment, these eggs hatch and with little residual activity of the insecticide, there is a gradual increase in louse numbers. The concept of retreatment after 10-14 days is to ensure that all surviving eggs have hatched and that no new eggs have been laid thus eliminating the louse population. An insecticide that destroys all life stages including the eggs would eliminate louse infestations and thus avoid the necessity of a second treatment. Studies with chlorpyrifos for control of lice on -cattle have shown this material to be highly effective with excellent ovicidal activity (Buchanan and Coles 1971; Loomis et al. 1976). Tests were therefore conducted to determine the effectiveness of this product for control of the sucking louse, Haematopinus suis (L.) on swine.

Materials and Methods

Thirty-five pregnant brood sows were divided into four test groups of eight to ten animals. Each sow was in an individual stanchion pen and test groups were separated such that no physical contact between groups was possible. All animals were housed in a low ceiling (ca. 2 m), poorly ventilated barn which had a single exhaust fan that ran continuously. The barn was completely enclosed with concrete floors, wood ceiling and sheet metal walls. At the time of this study no other insect control programs were ongoing nor had any spray programs occurred for at least two months. In addition to test animals, ca. 60 gilts and six boars were housed in the same barn and ca. 20 sows in a nearby non-connected farrowing barn.

One group of animals acted as controls and the others were treated at the rate of 10, 20 or 30 mg/kg. As no scales were available, sows were estimated to the nearest 20 kg by the producer. Sows ranged in weight from ca. 140-200 kgm. The non-treated animals were located furthest from the single exhaust fan to

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Proceedings of the Entomological Society of Ontario Volume 110, 1979

minimize possible vapour effects. A louse index per animal was determined by the number of lice observed on the face, sides of neck and backline to the rear of the front shoulders. A pretreatment count was made on Oct. 5/78 and animals then treated using a single spot-on treatment of chlorpyrifos, Dursban®44. The ready- to-use formulation was applied from a plastic squeeze applicator to the centre of the backline at the rate of 1, 2, or 3 ml per 45 kg dependent on treatment group.

Many of the animals in the treatment barn were observed with large concen- trations of louse eggs, particularly on the sides of the neck. Since no reinfestation had occurred by 28 days posttreatment, hair samples were removed from animals of each test group. Samples were also taken from sows in the nearby farrowing barn where adults and nymphs were still active. Samples were removed using | electric clippers, coded by test group and examined in the laboratory within four hours. Eggs were classified as unhatched based on the presence of an operculum. Each unhatched egg was then squeezed with forceps until the chorion was broken. If embryonic fluid was present the egg was considered viable; if no fluid was present the egg was classified as desiccated and non-viable.

Results and Discussion

Immediately after treatment a strong insecticidal odor permeated the barn and was evident at the time of the first posttreatment count, 18 hrs later. The producer indicated that this odor persisted for approximately four days, but no adverse effects were noted to animals in the three treatment groups. These observa- tions agreed with Loomis et al. (1976) who found no adverse effects to calves except three animals treated at dosages at least three times higher than those of this study. At dosages of 100-200 mg/kg cattle showed signs of organophosphate toxicity within five minutes but were fully recovered within 90 minutes (Loomis et al. 1976).

The effect of chlorpyrifos on populations of adults and nymphs is presented in Table I. Eighteen hours posttreatment no live lice could be found on any of the treated animals; whereas, louse indices on control animals remained similar. Post- treatment counts 6, 21, 28 and 42 days later also failed to reveal any lice on treated animals. Six days posttreatment no lice could be found on the non-treated controls. The producer insisted that these animals had been neither treated nor moved. Visual inspection of ca. 20 gilts and six boars which were not treated but housed within the same barn also revealed that these were free of lice despite having moderate infestations prior to treatment. Sows in the nearby non-connected farrowing barn were then examined and found still to have moderate infestations of lice.

TABLET. Effect of chlorpyrifos (Dursban® 44) on populations of Haematopinus suis, Fergus, Ontario, 1978.

Mean Louse Index/ Animal Posttreatment at Hours (h) and Days (d) indicated

No. of Animals Dosage Pretreatment 18h 6d 21d 28d 42d 8 30 mg/kg 42.6 0 0 0 0 0 9 20 mg/kg 20.6 0 0 0 0 0 10 10 mg/kg 32.3 0 0 ) 0 0) 8 control in 17.8 23.4 0 0 0 0 same barn

Proceedings of the Entomological Society of Ontario Volume 110, 1979

Although egg samples were examined without prior knowledge of treatment group, it became evident which hair samples were from sows in the treatment barn and which were from sows in the nearby farrowing barn. On hair samples from sows in the treated barn (Fig. 1 A & C), all eggs were ca. 2.5 cm from the base

{

FIGURE 1. Haematopinus suis eggs collected from hair samples 28 days after treatment with chlorpyrifos: A and C, eggs in treated barn; B, eggs from non-treated barn.

of the hairs, whereas from the non-treated barn eggs extended to the base of the hair (Fig. 1 B). Egg production had ceased on sows in the treated barn and as the hair grew eggs were extended further from the body. Eggs also showed a definite pattern as to whether they were hatched or unhatched. Those on the outer regions of the hair had hatched whereas those on the inner regions remained unhatched. The majority of these eggs were non-viable and in most instances a desiccated, nearly complete embryo was observed by identification of legs and tarsal claws.

The results of the egg samples are presented in Table II. Of the 129 eggs collected from untreated sows in the nearby farrowing barn, 12.4% were viable as compared to an overall viability of 0.58% of 689 eggs collected from sows in the test and control groups in the treatment barn. The eggs classified as viable

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Proceedings of the Entomological Society of Ontario Volume 110, 1979

TABLE II. The condition of Haematopinus suis eggs taken from untreated and chlorpyrifos treated animals 28 days posttreatment, Fergus, Ontario, 1978.

Percentage Treatment No. of Eggs Hatched Desiccated Viable 30 mg/kg 197 67.6 31.0 1.5 20 mg/kg 153 B52) 64.7 0 10 mg/kg 131 32.0 67.9 0 Checks inside barn 208 91.3 8.1 .04 Total 689 60.8 38.6 0.58 Checks outside barn 129 84.4 Bll 12.4

inside the treatment barn still contained some embryonic fluid but were 2.5 cm from the hair base and because of the location on the hairs were presumed to be ca. four weeks of age and thus of questionable viability. On treated animals, 30-68% of the eggs were unhatched and desiccated as compared to less than 10% of the eggs on non-treated animals. Although no nymphs, adult lice and only (.04% ) one viable egg could be found on non-treated animals within the treatment barn, the percentage of unhatched desiccated eggs was considerably lower than that of treated animals; 8.1% as compared to 31-68%. This indicates that some eggs on non-treated animals were unaffected by insecticide vapours but that nymphs were destroyed once the eggs hatched.

Buchanan and Coles (1971) found 2% hatchability from eggs of cattle lice Linognathus vituli (L.) and Damalinia bovis (L.) when hair patches were sprayed with 250 ppm chlorpyrifos. Loomis et al. (1976) found similar results when chlorpyrifos was applied as a spot-on treatment to the backline of cattle. Three possible mechanisms exist by which chlorpyrifos reaches lice and their eggs. These include; 1) contact toxicity, as would be observed on whole body sprays of animals, 2) systemic activity as suggested by Loomis et al. (1976) and 3) fumigant action.

This study strongly suggests that at least part of the mortality resulting from a single spot-on treatment with chlorpyrifos was caused by fumigant action. With this type of application method, direct contact toxicity over the entire body of the animal is not possible. Although Claborn et al. (1968) showed residues of chlor- pyrifos particularly in the fat of cattle for up to five weeks after treatment, it is believed that the systemic activity of chlorpyrifos did not cause appreciable louse mortality particularly against the eggs. The mode of action by which chlorpyrifos residues can reach eggs on relatively inert hairs is difficult to explain by systemic action.

Most registered products for control of cattle grubs aid in the reduction of louse populations but do not give complete control because eggs are unaffected by treatment. Systemic activity of chlorpyrifos does not affect Hypoderma spp. when applied as a whole body spray at a rate of 35 mg/kg (Drummond 1966) yet in this trial complete control of lice including eggs occurred at dosages of 30 mg/kg and less. Chlorpyrifos has been shown ineffective against Sarcoptes scabei suis Gerlach when applied as a pour-on at 20 mg/kg (Galloway and Westwood un- published). This would suggest complete louse control in this study cannot be explained by systemic action. Although chlorpyrifos has a moderate vapour pressure of 1.87 x 10° mm Hg at 25°C (Dow Chemical Co. 1965), Kenega et al. (1965) showed that the insecticide was sufficiently volatile to form residues on

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Proceedings of the Entomological Society of Ontario Volume 110, 1979

surfaces of nearby objects. They found in laboratory studies that residues from vapours were sufficient to control houseflies and aphids 24 hr after exposure to chlorpyrifos vapours. This presents the possibility that control in this study was due to fumigant action. It also would explain the control of lice on untreated animals and agree with the observation of a strong insecticidal odor which per- sisted for at least four days following treatment.

These data provide additional evidence that chlorpyrifos is ovicidal and provides complete control of lice with a single low dose spot-on treatment, thus avoiding the necessity of follow-up treatments. The data also suggest the possi- bility of controlling lice on animals without actually treating the individual animals. This could have practical implications for control of lice or mites on poultry where large numbers of individual birds are present and individual treat- ment may be prohibitive.

Acknowledgments

This research was supported by the Ontario Ministry of Agriculture and Food and a grant-in-aid from Dow Canada Limited.

References

BUCHANAN, R. S. and P. G. CoLeEs. 1971. Control of lice on cattle with Dursban. N. Z. Vet. J. 19: 197-202.

CLABORN, H. V., R. A. HOFFMAN, H. D. MANN and D. D. OEFHLER. 1968. Residues of Dursban and its oxygen analog in the body tissues of treated cattle. J. econ. Ent. 61: 983-986.

Dow CHEMICAL COMPANY. 1965. Dursban insecticide technical information. Brochure 1-224, February 25. Bioproducts Department, Midland, Mich. 48641.

DRUMMOND, R. O. 1967. Further evaluation of animal systemic insecticides, 1966. J. econ. Ent. 60: 733-737.

GALLoway, T. D. and R. WESTWoop. 1979. Unpublished report. Department of Entomology, University of Manitoba, Winnipeg, Manitoba R3T 2N2.

._KENAGA, E. E., W. K. WHITNEY, J. L. Harpy and A. E. Doty. 1965. Laboratory tests with Dursban insecticide. J. econ. Ent. 58: 1043-1050.

Loomis, E. C., A. N. WEBSTER and P. G. Loss. 1976. Trials with chlorpyrifos (Dursban) as a systemic insecticide against the cattle louse. Vet. Rec. 98: 168-170.

Received 15 June 1979)

Proceedings of the Entomological Society of Ontario Volume 110, 1979

Proceedings of the Entomological Society of Ontario Volume 110, 1979

THE EFFICACY OF SELF-APPLICATING DEVICES FOR CONTROL OF THE FACE FLY, MUSCA AUTUMNALIS (DIPTERA: MUSCIDAE) AND THE HORN FLY, HAEMATOBIA IRRITANS (DIPTERA: MUSCIDAE) ON CATTLE NEAR GUELPH, ONTARIO’

L. A. BARLOW and G. A. SURGEONER

Department of Environmental Biology, University of Guelph, Guelph, Ontario NIG 2W1

Abstract Proc. ent. Soc. Ont. 110: 9-17 (1979)

The efficacy of several, self-applicating devices and insecticides in controlling the face fly, Musca autumnalis DeGeer, and the horn fly Haematobia irritans (L.) on cattle, was evaluated. The free-choice devices tested were the Injecto-Rub® oiler with 1% crotoxyphos and the Dr-Scratch® back rubber with 3% stirofos dust. A forced-use device, the Farnam Walk-Way® oiler containing Ciovap® (1% crotoxyphos and 0.25% dicrlorvos) and a combination forced-use and free-choice device, the Tox-O-Wik® beef oiler containing 1% malathion and 2.5% methoxy- chlor, were also evaluated.

Only the Tox-O-Wik® beef oiler provided a significant reduction in the populations of the face fly. Free-choice devices did not provide satisfactory control of the horn fly whereas forced-use and combination forced-use and free- choice devices provided excellent control of this insect.

Introduction

The face fly, Musca autumnalis DeGeer, is an introduced pest of cattle and horses in Ontario. Since its initial discovery in Nova Scotia (MacNay 1952), it has spread rapidly throughout North America such that, by 1970, it has been reported from the southern parts of all the provinces in Canada, and most of continental United States (Depner 1969; Smith and Linsdale 1969).

The face fly irritates cattle by feeding on lachrymal and nasal secretions. Maximum numbers occur in July and August and have been observed to be as high as 75 to 100 per animal (Wrich 1970). Although in North America, the face fly is believed to cause reduced milk-yields and weight gains (Teskey 1960), it is not considered a pest of economic importance in Europe (Benson and Wingo 1963). There is evidence that the face fly causes pinkeye in cattle (Brown and Adkins 1972) and transmits several species of Thelazia sp. (Spirurata: Nematoda) to the eyes of cattle and horses (Branch and Stoffolano 1974). Annual losses attributable to the face fly in the United States were estimated to be $68 million from 1959 to 1961 and $140 million from 1973 to 1975 (ARS National Research Program 1976).

Attempts to control the face fly on cattle have consisted of diets containing insecticides, aerial-spraying with ultra-low volumes of insecticides, and applying insecticides or repellents manually using devices such as oil cans, brushes and sprayers. These efforts have been generally unsatisfactory (Ode and Matthysse 1964; Dorsey et al. 1966; Kantack et al. 1967). Self-treatment, insecticide- applicating devices, primarily swing-type back rubbers, tank-type oilers, and dust bags, have been studied in forced-use and free-choice positions. Although the reductions in the face-fly populations have often been unsatisfactory, there have

* From a thesis submitted by L. A. Barlow in partial fulfillment of the requirements of the M.Sc. degree, University of Guelph, 1978.

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Proceedings of the Entomological Society of Ontario Volume 110, 1979

been reports of self-applicating devices providing satisfactory reductions (Hair and Adkins 1965; Seawright and Adkins 1968; Poindexter and Adkins 1970; Kessler and Berndt 1971; Ronald and Wingo 1973).

The efficacy in controlling the face fly using several types of self-applicating devices was evaluated. These devices, with one exception, had not been evaluated before. The mop-type device had been tested, but not extensively (Wright 1971). The effects of these devices and insecticides on populations of horn fly, Haema- tobia irritans (L.), were also observed.

Materials and Methods

During the summers of 1975 and 1976, privately-owned cattle herds in the vicinity of Guelph were used to evaluate the self-applicating devices. Between two and five pretreatment counts of flies were taken on each of the test and the check (untreated) herds. The average distance between herds was approximately eight kilometers. Counts of flies on the check herds were made on the same days as counts of flies on the test herds. After the installation of the devices, usually in mid-July to early August, such parallel counts on the test and the check herds were continued for one to two months, at approximately weekly intervals. Fly- counts were usually made between 10:00 hr and 16:00 hr. The cattle were usually at least 30 m from farm buildings when fly-counts were made. The first author made all the counts during both summers.

In the counting procedure, individual animals were approached and the face flies on the face, on one side, and the horn flies on one side were counted. Occasionally, 7 x 35 binoculars were used to aid the counting. In 1975, attempts were made to count the flies on 20 animals. In 1976, the sample size was reduced to 15 animals.

For each day on which flies were counted, the mean number of face flies per face, per side, and the mean number of horn flies per side for each test and check herd were calculated. The differences between the check and the test means ob- tained on the same day were tested for significance by an APL T-test program. To remove the observed correlation between fly count means and variances, the raw data was transformed by log. (c + 1) before the analysis. The variable c was the number of flies per animal. Two tailed T-tests were done on the differences between test and check means observed before the initiation of treatment. If the test means were less than the check means after the initiation of treatment, one tailed T-tests were performed. The significance level used was p = .0O1. This was done to keep the experiment-wise error at a minimum. Where reductions attribut- able to treatment occurred in the face-fly or horn-fly populations on cattle with access to the self-applicating devices, the percentage reductions of flies were calculated using a modified Abbott’s formula (Henderson and Tilton 1955).

TA: wiCB X TBE

TA and CA were the grand mean numbers of flies on the test and the check herds, respectively, after the initiation of a treatment. TB and CB were the grand means before the initiation of a treatment. A grand mean was calculated by averaging the test or the check means obtained before or after the initiation of a treatmeant.

Percentage reduction = (1 - Nexo hOO

The devices tested were the Injecto-Rub® oiler (angle-type), the Dr. Scratch® back rubber, the Tox-O-Wik® beef oiler (combination forced-use and free-choice),

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Proceedings of the Entomological Society of Ontario Volume 110, 1979

and the Farnam Walk-Way® oiler (mop-type). The Injecto-Rub® oiler consisted of an insecticide tank bolted to a post and attached to a steel cable which func- tioned as a rubbing element. The rubbing element was anchored at an angle to the ground. When cattle rubbed against the steel cable, a pumping device delivered the insecticide formulation to the cable. At each of two farms, the oiler was installed on the pasture near salt blocks and sources of water for the cattle. At a third farm, the oiler was installed inside a “loafing” shed which contained a supply of salt. The insecticide formulation used in these oilers was diesel fuel oil contain- ing 1% crotoxyphos.

The Dr. Scratch® back rubber consisted of a hollow rubber cylinder sus- pended horizontally between two steel posts. The cylinder was attached to a plastic bag containing 3% stirofos dust. The dust was discharged from several small holes distributed along the lower surface of the cylinder when cattle rubbed against the latter. This device was installed on a pasture near salt blocks.

The Tox-O-Wik® beef oiler consisted of an angle-type rubbing element and an insecticide tank from which a rubber apron was suspended. The lower margin of this apron consisted of an inch- thick ring of canvas connected to the inside of the tank by a wick. The rubber apron was suspended above a rubber tub containing mineral supplement. The purpose of the rubber apron was to force cattle intending to feed on the supplement to brush their faces against the insecticide-saturated ring of canvas. The oiler was installed on a pasture near the barn and filled with kerosene containing 1% malathion and 2.5% methoxychlor.

The Farnam Walk-Way® oiler consisted of an insecticide tank from which a mop-like rubbing element was suspended. When the rubbing element was moved by cattle passing under it, small quantities of the insecticide were discharged into the element from the tank by a pumping device. The oiler was hung in the door- way to the milking parlour and filled with Ciovap® (1% crotoxyphos and 0.25% dichlorvos) such that the animals used it four times a day.

Once the Injecto-Rub® oilers, the Farnam Walk-Way® oiler in 1975, and the Dr. Scratch® back rubber were installed, they were kept on the farms for the entire summer. The cattle, which had access to the Farnam Walk-Way® oiler in ~1976 and the Tox-O-Wik® beef oiler, were separated from their devices after 46 and 31 days respectively, to determine what effect this would have on the fly- populations.

Results Free-choice Devices

The face fly and horn fly numbers on cattle with access to the free-choice, self applicating devices are presented in Figs. 1 and 2. The number of face flies on the faces of cattle in two herds, each with access to an Injecto-Rub®, containing 1% crotoxyphos (Ciodrin®), were not significantly different from those on nearby check herds (Figs. 1a, c). Numbers of horn flies per side were significantly lower on the treated animals compared to controls on all sampling dates after the installation of the oiler (Fig. 1b, d). The reductions were 58% and 85% respec- tively.

The number of face flies per face on cattle with access to the Injecto-Rub® oiler, containing 1% crotoxyphos, installed in a loafing shed frequented by cattle was usually not significantly different from that of the check herd (Fig. 2a). There was an 84% reduction in the number of horn flies per side on the treated cattle

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Proceedings of the Entomological Society of Ontario Volume 110, 1979

52 (b)

350

175 Oc LJ aa T aly T T S15 i940 tien 27s leres 5, 19 4 tie, 2) tenes S JUNE JULY AUG JUNE JULY AUG. zd S 30 225 TREATMENT S ©) — —CHECK @ A + TREATMENT INITIATED > S

20 I50 fee

ns i

28 13 2eti3 27 12 27 28 13 «2813 27 2 27 JULY AUG. SEPT JULY AUG. SEPT

DATE

FicurE 1. Fly populations on cattle with access to the Injecto-Rub® oiler containing 1% crotoxyphos, 1976. Mean number of Musca autumnalis per face (a) and Haematobia irritans per side (b) respectively, at first farm. Mean number of M. autumnalis per face (c) and H. irritans pert side (d) respectively, at second farm. s = difference between means significant p. = .01, ns = difference not significant.

(Fig. 2b). No significant reductions in face fly (Fig. 2c) or horn fly (Fig. 2d) numbers were observed on cattle with access to the Dr. Scratch® back rubber containing 3% stirofos (Rabon®) dust.

Combination Forced-use and Free-choice Device

There was no significant reduction in the number of face flies per face on cattle with access to the Tox-O-Wik beef oiler containing 1% malathion and 2.5% methoxychlor (Fig. 3a). An 86% reduction in the number of face flies per side was observed on test cattle while they had access to the oiler (Fig. 3b). Removal of the device was followed by an increase in the number of face flies per side. While the cattle had access to the device, the horn fly density was zero on every sampling date but the first (Fig. 3c). The overall reduction during this period was 85%. When the oiler was removed a small increase in the horn fly density on the test cattle to three per side, on September 3, was observed.

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Proceedings of the Entomological Society of Ontario Volume 110, 1979

21 A 240

l60

ie 80 Or Lu = 28 a1. 6 20, , 7 19 28 Blan 5 20, 7 IO S JUNE JULY AUG. SEPT JUNE JULY AUG. SEPT. Zz

30 6004 ——TREATMENT @ - — —CHECK <I 25 TREATMENT = LJ INITIATED = 20 400

5

10 200

5

» liwer22 10 '28 AS) 2 20 4 22 io" 2BrtS 2.20 JUNE JULY AUG. SEPT. JUNE JULY AUG. SEPT.

DATE

FIGURE 2. Mean number of Musca autumnalis per face (a) and Haematobia irritans per side (b) on cattle with access to an Injecto-Rub® oiler filled with 1% crotoxyphos and installed in a loafing shed, 1976. Mean number of M. autumnalis per face (c) and H. irritans per side (d) on cattle with access to a Dr. Scratch® back rubber containing 3% stirofos dust, 1976. s = difference between means significant at p = .01, ns = difference not significant.

Forced-use Devices

There was no significant reduction in the number of face flies per face of cattle using the Farnam Walk-Way® oiler, containing 1% crotoxyphos and 0.25% dichlorvos (Ciovap®, in 1975 and 1976 (Fig. 4a, c). Removal of the oiler in August 1976, was followed by a decrease in face fly numbers on test and check animals. This provided additional evidence that the device had no treatment effect.

In 1975 and 1976, there were 100% reductions in number of horn flies per side on cattle with access to the oiler (Fig. 4b and d). Removal of the oiler in 1976 was followed by an increase in the horn flies on the test cattle to levels that were not significantly different from the check animals.

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Proceedings of the Entomological Society of Ontario Volume 110, 1979 30

20

10 ad Lu S aa) = ¢ 4 4 =i PRS FoteeO iSjacite a “6 a 30° 6 eee JUNE JULY AUG. JUNE JULY AUG. F300 (C) TREATMENT Li — (== CHECK = * TREATMENT INITIATED 56 | TREATMENT TERMINATED \ 100 WA \ » 2 18. 4 120.5%. an 6 JUNE JULY AUG.

DATE

FIGURE 3. Mean number of Musca autumnalis per face (a), per side (b), and Haematobia irritans per side (c) on cattle with access to the Tox-O-Wik® beef oiler containing 1% malathion and 2.5% methoxychlor, 1976. s = difference between means significant at p = .01, ns = difference not significant.

Discussion

There were no significant reductions in the numbers of the face fly on the faces of cattle with access to the free-choice, combination forced-use and free- choice, and forced-use devices. A significant reduction occurred in the number of face flies on the sides of cattle with access to the combination forced-use and free-choice device, the Tox-O-Wik® beef oiler. However, the face-fly densities on the test cattle were almost always greater than 8-10 per face and 5-10 per animal, postulated as annoyance levels by Hansens (1961), DeFoliart (1963), and Hansens and Granett (1963). Therefore, the reduction in the face-fly numbers was not sufficient to prevent possible economic loss. There was no benefit to installing the angle-type oiler in a shed in which the cattle frequently congregated.

Benson and Wingo (1963), Kessler and Berndt (1971), Wright (1971) and Ronald and Wingo (1973) also found that free-choice and forced-use devices

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Proceedings of the Entomological Society of Ontario Volume 110, 1979

45

225

30

150

75

om a 2) ASI 28)) 139! 127 eal2 27 28 13 ‘28 13 27 12 27 > MAY JUNE JULY = AUG. MAY JUNE JULY AUG. 320 300 TREATMENT

imam CHECK > ¢ TREATMENT INITIATED xa 4 TREATMENT TERMINATED Lu6o0 200 =

30 Leze)

2 20) 8, 4,26 AS 3 18 JUNE JULY AUG. JUNE JULY AUG.

DATE

FIGURE 4. Fly populations on cattle using the Farnum Walk-Way® oiler containing 1% cro- toxyphos and 0.25% dichlorvos. Mean number of Musca autumnalis per face (a) and Haema- tobia irritans per side (b) respectively, 1975. Mean number of M. autumnalis per face (c) and H. irritans per side (d) respectively, 1976. s = difference between means significant at p =.01, ns = difference not significant.

were ineffective in controlling the face fly. However, workers such as Dobson and Huber (1961), Hair and Adkins (1965), Turner (1965) and Poindexter and Adkins (1970) reported that free-choice and forced-use devices provided large reductions in the face-fly populations on the test cattle. Since a larger number of devices were tested in these four studies than in others including the present one, in which face-fly control was ineffective, area-wide reductions of the face-fly populations could have occurred.

There was excellent control of the horn fly on cattle using the forced-use and combinations forced-use and free-choice devices. The reductions in the horn-fly numbers were erratic on the herds with access to the free-choice devices. Where reductions occurred, namely on three herds with access to angle-type oilers, the average horn-fly densities were often greater than 10 or 50 per animal, postulated as economic injury levels by Dobson and Peterson (1963) and Morgan (1967).

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Proceedings of the Entomological Society of Ontario Volume 110, 1979

Therefore, some economic loss due to the horn fly could have occurred on these herds.

Workers such as Kessler and Berndt (1971) also have noted that control of the horn fly was greater than that of the face fly on herds with access to self- applicating devices. This difference can probably be explained by several factors. The face fly is a highly dispersive insect (Ode and Matthysse 1967) and although flies which alight on treated animals may die, the continuous redistribution of flies prevents reduction of the population on a single herd. This phenomenon has been demonstrated in studies of feed-through insecticides (Hall and Foehse 1979). Face flies tend to congregate on the facial area which generally receives little insecticide since cattle tend to lower their heads when passing under a self-applicating device. Much of the insecticide that is applied to the face is probably removed by lach- rymal and nasal secretions. These factors increase the difficulty of reducing the face-fly population on the faces of cattle. Horn flies are less dispersive than face flies and congregate on the back which cattle readily treat by passing under a self-applicating device. Furthermore, horn flies remain on cattle for greater periods of time, leaving only to oviposit or when disturbed.

The variation in the reductions of the horn-fly populations and, to a lesser extent, of the face-fly populations, could have been due partly to the different insecticides and insecticide formulations used in the devices. The reductions in the horn-fly populations on cattle using the forced-use and combination forced-use and free-choice devices were greater than those on cattle using the free-choice devices. This suggests that different frequencies of use of the devices by the cattle contributed to the variation.

The Dr. Scratch® back rubber containing 3% stirofos dust was the only device that did not provide a significant reduction in the horn-fly population on the test cattle. This is unusual since horn-fly populations are generally easy to control. The reason for this lack of control is unknown. On every sampling date after the initiation of the treatment, insecticidal dust was observed on the ground, at the base of the back rubber. On several occasions when cattle were observed using the device, dust was seen being applied to the backs of the animals. How- ever, these were casual observations and an accurate determination of the fre- quency of use was not done.

Acknowledgments

This research was supported by N.R.C. operating grant No. A0Q588 and the Ontario Ministry of Agriculture and Food. We also thank Mr. W. Kirkwood and Mr. D. Hamilton for technical assistance.

References

ARS NATIONAL RESEARCH PROGRAM. 1976. NRP No. 20480. Control of insects affecting livestock. U.S. Dep. Agric. ARS. 99 pp.

BENSON: O. L. and C. W. WINGO. 1963. Investigations of the face fly in Missouri. J. econ. Ent. : 251-258.

BRANCH, C. J. and J. G. STOFFOLANO. 1974. Face fly; invertebrate vector and host of a Mammalian eye worm in Massachusetts. J. econ. Ent. 67: 304-305.

Brown, J. F. and T. R. ADKINS, Jr. 1972. Relationship of feeding activity of face fly (Musca

autumnalis DeGeer) to production of keratoconjunctivitis in calves. Am. J. vet. Res. 33: 2551-2555.

DEFOLIART, G. R. 1963. Preventive spraying schedules for dairy farm fly control. J. econ. Ent. 56: 649-654.

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Proceedings of the Entomological Society of Ontario Volume 110, 1979

DEPNER, K. R. 1969. Distribution of the face fly, Musca autumnalis (Diptera: Muscidae), in western Canada and the relation between its environment and population density. Can. Ent. 101: 97-100.

Dosson, R. C. and D. A. HUBER. 1961. Control of face flies (Musca autumnalis) on beef cattle in Indiana. J. econ. Ent. 54: 434-436.

Dosson, R. C. and R. C. PETERSON. 1963. Horn fly control on beef cattle by the use of cable rubbers. J. econ. Ent. 56: 230-234.

Dorsey, C. K., J. O. HEISHMANN and C. J. CUNNINGHAM. 1966. Face fly and horn fly control on cattle — 1962-64. J. econ. Ent. 59: 736-732.

Hair, J. A. and T. R. ADKINS, JR. 1965. Dusting stations and cable back rubbers as self- applicatory devices for control of the face fly. J. econ. Ent. 58: 39-41.

HALL, R. D. and M. FoeEHSE. 1979. Cattle, control of Diptera in beef cattle manure with free- choice Rabon® oral larvicide, 1978. Insecticide and Acaricide Tests 4: 210-212.

HANSENS, E. J. 1961. Face fly promises to become no. 1 cattle problem in NE. New Jersey Agric. 43: 11-12.

HANSENS, E. J. and P. GRANETT. 1963. Tests of Ciodrin and other materials against face fly, Musca autumanalis. J. econ. Ent. 56: 24-29.

HENDERSON, C. F. and E. W. TILTON. 1955. Tests with acaricides against brown wheat mite. J. econ. Ent. 48: 157-161.

KANTACK, B. H., W. L. BERNDT and E. V. BALSBAUGH, JR. 1967. Horn fly and face fly control

on range cattle with aerial applications of ultra-low-volume malathion sprays. J. econ. Ent. 60: 1766-1767.

KESSLER, H. and W. L. BERNDT. 1971. Comparison of dust bags to back rubbers for control of horn flies and face flies on beef cattle in east-central South Dakota. J. econ. Ent. 64: 1465-1466.

MacNay, C. G. 1952. New records of insects in Canada, 1952. A. Rep. ent. Soc. Ont. 83: 69, 92

Morean, N. O. 1967. Control of horn flies by an electrochemical device. J. econ. Ent. 60: 750-752.

Ope, P. E. and J. G. MatTruysseE. 1964. Face fly control experiment. J. econ. Ent. 57: 63 1-636.

ObE, P. E. and J. G. MATTHYSSE. 1967. Bionomics of the face fly, Musca autumnalis DeGeer. Mem. 402. Cornell Univ. Agr. Exp. Sta. N.Y. State Coll. Agr., Ithaca, N.Y.

POINDEXTER, C. E. and T. R. ADKINS, Jr. 1970. Control of the face fly and the horn fly with self-applicatory dust bags. J. econ. Ent. 63: 946-948.

RONALD, N. C. and C. W. WINGO. 1973. Cost and effectiveness of horn fly and face fly control programs in semi-isolated range herds in central Missouri. J. econ. Ent. 66: 693-696.

SEAWRIGHT, J. A. and T. R. ADKINS, Jr. 1968. Dust stations for control of the face fly in South Carolina. J. econ. Ent. 61: 504-505.

SmiTH, T. A. and D. D. LinspALe. 1969. Third supplement to an annotated bibliography of the face fly, Musca autumnalis DeGeer, in North America (with supplements 1, 2, 3). California Vector Views 13 (6).

TESKEY, H. J. 1960. A review of the life-history and habits of Musca autumnalis (Diptera: Muscidae). Can. Ent. 92: 360-367.

TURNER, Jr., E. C. 1965. Area control of the face fly using self-applicating devices. J. econ. Ent. 58: 103-105.

Wricu, M. J. 1970. Horn fly and face fly control on beef cattle using back rubbers and dust bags containing coumaphos or fenthion. J. econ. Ent. 63: 1123-1128.

WriGHT, R. E. 1971. Control of face fly and horn fly. Pesticide Research Report, Canada Committee on Pesticide Use in Agriculture. p. 196.

(Received 18 January 1979) 17

Proceedings of the Entomological Society of Ontario Volume 110, 1979

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Proceedings of the Entomological Society of Ontario Volume 110, 1979

FLIGHT ACTIVITY OF THE GREEN PEACH APHID (HOMOPTERA: APHIDIDAE) DURING THE VEGETABLE GROWING SEASON AT HARROW AND JORDAN, ONTARIO

W. M. ELLIOTT Research Siation, Agriculture Canada, Harrow, Ontario NOR 1G0

W. G. KEMP Research Station, Agriculture Canada, Vineland, Ontario LOR 2E0

Abstract Proc. ent. Soc. Ont. 110: 19-28 (1979)

Flights of the green peach aphid, Myzus persicae (Sulzer), were monitored from June to September, using suction traps at Harrow and yellow sticky traps at Jordan, Ontario from 1970 to 1976. In 1970-1975 the correlation coefficients be- tween catches at these locations were significant (P = 0.02). In 1976 no inter- location correlation occurred and the unimodal curve of abundance found in other years at the two sites, did not occur. Unusually large flights in early 1976 at both locations could be attributed at least in part to warm weather in April and in the previous November, but the differences between the subsequent numbers trapped at Harrow and Jordan in 1976 could not be explained. The data are given in full for reference by subsequent workers studying alate aphid abundance and aphid-borne virus epidemiology in Ontario.

Introduction

Flying aphid populations have been monitored by suction traps at Rotham- sted, England since 1947 (Johnson 1950) and data from a permanent network of suction traps, established in 1968, are used to issue weekly aphid bulletins and annual summaries (Taylor and French 1978). This network includes 20 traps in Great Britain and others in Holland and Denmark. The weekly aphid bulletins are used to advise growers of seed potato, sugar beet and field beans on the probability of virus damage or direct aphid injury if top killers or insecticides are not applied. -Grower warning systems for green peach aphid (GPA), Myzus persicae (Sulzer) invasion of seed potatoes, based on yellow water trap catches, have been in use since the 1950’s in Europe (Hille Ris Lambers 1955; Robert 1976). In Canada GPA trapping schemes for warning seed potato growers of seasonal aphid activity already exist in New Brunswick (MacGillivray 1977) and British Columbia (Weintraub 1977), also based on yellow water trap catches.

The abundance of flying GPA has been recorded at Harrow, Ontario, using suction traps and at Jordan, Ontario, using yellow sticky traps since 1967 and 1970 respectively (Elliott 1971; Kemp and Troup 1978). At Harrow the principal interest was in the likelihood and intensity of new infestations on vegetables starting at different times of year whereas at Jordan the data were used in studies on the epidemiology of stylet-borne, non-persistent viruses, particularly cucumber mosaic virus (CMV) in green peppers (Capsicum frutescens L.), which is vectored by the GPA.

The GPA is common on vegetable crops and tobacco in southern Ontario and would become more important, attracting more interest in monitoring, if there were an increase in susceptible crops grown, or in virus diseases. Aphicides could be withdrawn for environmental or health reasons or due to development of resistance, which appears to be happening (R. J. McClanahan, pers. comm).

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Proceedings of the Entomological Society of Ontario Volume 110, 1979

The objective of this paper is to make available data on seasonal aphid flights in the peach and vegetable growing areas of southern Ontario. This may assist later workers in assessing whether their catches are unusually high or low and early or late. Furthermore, it is important to know if the activity of the GPA at opposite ends of the S.W. Ontario vegetable growing area are similar when considering the applicability to one site of conclusions drawn from the other. Harrow data prior to 1971 were previously reported (Elliott 1971). The Jordan data have not been published before.

The Harrow and Jordan sites are influenced by about 800 and 2,700 hectares of peach orchard respectively in the surrounding areas. These are early sources of aphids which are much less extensive in the counties between the sites. The growing season of 155-165 frost-free days and 3300 corn heat units at Harrow and Jordan also differs from that in the vegetable growing areas between them (<155 frost free days and 2900-3300 corn heat units).

Methods

Alate GPA were monitored at Harrow from April to November, 1970 to 1976 with two suction traps and procedures somewhat modified from those of Elliott (1971). A one-gallon reservoir was connected to the aphid collecting jar by PVC tubes to maintain sufficient ethyl alcohol in the jar for a week. Insects were removed from traps at weekly intervals and on the same day of the week as far as possible. When catches were large they were subsampled and the count of GPA in whole catches was calculated. Samples of the 1976 GPA were cleared, dehydrated and mounted on microscope slides by the method of Richards (1964) and examined under 100 X magnification. Lateral abdominal tubercles were counted to determine the origin of the unusually large early July catches by the method of Woodford and Lerman (1977).

The “Insectary” suction trap, located near the Harrow Research Station insectaries, was adjacent to vegetable plots and mowed grass to the S., continuous corn to the W. and farm buildings and houses to the N. and E. It caught insects flying 1 m above the ground (Elliott 1971).

The similar “Ridge Farm” suction trap was located on the Ridge Farm property of the Harrow Research Station, about 3.2 km S.E. of the insectary site. A peach orchard located to the E. and S. of this trap had been planted in 1969 and possibly exercised more influence on the catches each year as the trees grew. On the N. and W. side there was a small building and an irrigation pond with plots of vegetables further away on the N. side. Usually plant growth and farm operations start earlier at Ridge Farm, which is on Fox sandy loam soil, than at the insectary site which is on a finer sandy loam soil.

Estimates of the aerial populations of alate GPA at Jordan, Ontario were made from weekly catches on sticky traps located among unsprayed green bell pepper plots on the Pond Farm property of the Agriculture Canada, Vineland Research Station, immediately E. of the Jordan Harbour inlet on Lake Ontario. Traps were constructed from wooden stakes 90 x 7.5 x 2 cm, painted white and driven into the ground. A 16.5 x 7-cm yellow band encircled the stake 7.5 cm from the top. Clear cellulose acetate cards each with a 15 x 6.5 cm trapping surface were attached to the yellow band on either side of each stake. Tree Tanglefoot® was applied from an aerosol can to the clear acetate cards which were 40 cm above the soil surface. Two cards from each of 3 to 6 traps were collected weekly, usually from the first week in June to the last week in September, examin-

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Proceedings of the Entomological Society of Ontario Volume 110, 1979

ed and alate GPA counted. The average catch of GPA/card/week was used for correlation analysis with the suction trap counts from the Harrow sites on the closest dates.

Degree-day accumulations based on a 10° C threshold (DD10) were cal- culated from the formula in Kemp and Troup (1978), using daily maximum and minimum temperatures. Hours of sunshine were recorded with a Stokes Campbell sunshine recorder.

Results

Annual Patterns of Flight Activity

The same general pattern of flight activity occurred each year at Harrow at both sites in the years 1970-75 (Tables I and II). The first alate aphids were caught in June and numbers increased to a peak, usually in August but once in late July. By October, flight activity had virtually ceased. However in 1976 they were first caught in May with 2, 13 and 35 caught on 17, 24 and 31 May respec- tively at the Ridge Farm site (not shown in Table II). The peak numbers for the year 1976 occurred in the first 2 weeks of July, when catches were low in other years. Catches then became subnormal with no August peak, only approaching normal in late September.

Numbers caught/card/week at Jordan in 1970-75 usually exceeded numbers caught/suction trap/week at Harrow (Table III). Numbers were low in June, increasing to a seasonal peak in August (once in July). The year 1976 was exceptional at Jordan with relatively high catches in June, not increasing as rapidly in July as in other years and not reaching a peak until mid September. 1976 was thus unusual at both locations but unique at Harrow and also quite unlike any year when both suction traps were operating from 1969 to 1978 (Elliott 1971 and unpublished ).

In May and early June 1976, 77-80% of the alate aphids captured at Harrow were fundatrigeniae (migrants from peach colonies) according to the criterion of Woodford and Lerman (1977), which is based on the number of lateral abdominal tubercles. In late June, 15% were fundatrigeniae and this declined to 2% by July with the rest of these large July catches being alienicolae (migrants from secondary hosts). The alate aphids forming this July peak were thus at least one generation removed from those in peach orchards. Colonies were easily found in well-kept peach orchards in Essex county in June 1976 and prompted sufficient enquiries from peach growers to justify a recommendation on control measures (Fisher 1976). No enquiries about the GPA on peach were received at Harrow in the other years of this study.

Differences Between 1976 and Other Years

DD10 accumulations prior to the early peaks of alate aphids in 1976 were not unusual except in April when >2X the mean for 1970-1975 occurred at Harrow and Jordan (Table IV). The DD10 accumulation in November 1975 exceeded the mean for 1969-1974 by >6X and >7X at Harrow and Jordan respectively. As would be expected, the sunshine hours in April 1976 and Novem- ber 1975 were also higher than in most other years, although not as high as the DD10 accumulation would lead one to expect. Thus the overwintering populations in 1975/76 were favoured by warm weather during mating and oviposition in the fall and during development of the eggs on peach in the spring. The numbers of

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Proceedings of the Entomological Society of Ontario Volume 110, 1979

TABLE IV. Weather data and fall catches of alate green peach aphids in (1970-1975) and 1976.

ihendady tei AEE Factor Period Location Mean = s.e. Range 1976°* DD10 April® Harrow 30.5 + 9.2 6.9 - 60.3 67.5 ei Jordan 19S ise 753 2 - 46 54.0 Pe Previous Nov." Harrow 6.8 + 2.4 Mop, NIB) 46.7 a Jordan 6.4 + 1.4 0.4 - 9.5 45.4 Sunshine April Harrow 182.3 + 6.8 157.8 - 201.4 229.9 Hours i Jordan ANC See 7/03 194 - 249 285.0 Previous Nov. Harrow eS 126 41.7 - 182.4 119.4 ¥e Jordan JUS aa!) 49.5 - 93.7 De7 Female Previous Harrow 180 + 52 54 - 353 80 alate (GPA) Sept.-Nov. trapped Male a a 32+ 6 16 - 48 39 alate (GPA) trapped

a April observations are from (1970-1976) but Fall observations are from (1969-1975), since a relationship is proposed between the number of peach migrants and weather in the previous November and April.

males and females flying to peach trees in the fall were not exceptionally high (Harrow data only, Table IV).

Correlation Analyses

The correlation coefficients between weekly catches at both Harrow suction trap sites and on cellulose acetate sticky cards at Jordan were significant at P = 0.02 in 1970-1975 (Table V). Catches at the Harrow sites were more closely correlated with each other in most years, and when all the years were amalgamat- ed, than catches from either site were with those from Jordan. The combined data ‘from the Harrow sites (using logwW Harrow site catches + 1) produced correla- tion coefficients with Jordan catches which were intermediate between the correla- tion coefficient of Jordan with each Harrow site catch separately in 1972 and 1973 or higrer than those between Jordan and the two sites separately in 1970, 1971, 1974 and 1975.

There was no correlation between the numbers caught at the Harrow locations and the Jordan site in 1976. This can be attributed to the exceptionally high early July catches and the very low August and September catches at Harrow. In addi- tion, the correlation between the two Harrow sites was lower in 1976 than in other years, although still significant (P = 0.05).

Regression Equations

Regression equations treating the Jordan catches as the dependent variable le. y = logw (Jordan catch + 1) and x = logw (S Harrow catches +1) for the years 1970-75 were not very similar, even though the correlation coefficients were high.

The regression coefficient ranged from 0.39 to 1.52 in the years 1970-1975. The intercept i.e. log (Jordan catch +1) when combined Harrow catches — 0)

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Proceedings of the Entomological Society of Ontario

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26

Proceedings of the Entomological Society of Ontario Volume 110, 1979

ranged from —0.69 to 1.41. Combined data for the 6 years with good agreement between Harrow and Jordan (1970-1975) gives the equation y — 0.81 x +0.56, whereas the inclusion of the disruptive 1976 data gives the equation y = 0.67 x -+0.73, implying 3 to 4 alate aphids per card would be caught at Jordan when none was caught at Harrow, during the season of the year when these observations would normally be taken.

Discussion

The generally larger catches on cellulose acetate sticky traps at Jordan rela- tive to suction traps at Harrow are not necessarily due to a difference between methods, because differences in efficiency of the methods could be evaluated only by using both methods at the same site over several years.

Significant agreement between the areas for six years is very deceptive since it is completely absent in the 7th year. Monitoring GPA activity at a few sites in the S.W. Ontario vegetable growing area is likely to leave sites where the trend is opposite to that observed at monitoring sites. The local demand for information, and the staff and facilities available should determine how much is done and extrapolations should not be made.

The difference between 1976 and the other years in the initial population of alate aphids is fairly well explained by the meteorological factors used by Kemp and Troup (1978) for predicting CMV, but the difference in trend at Harrow and Jordan which occurred in July 1976 is not. The population flying to peach trees in Fall 1975 was not exceptionally high but conditions for sexual reproduction were favourable. The 1976 migration from peach was heavy and early but there- after differences occurred between Harrow and Jordan which we have not identified. Alate aphids of the July peak at Harrow were morphologically distinct and therefore = 1 generation removed from those produced by colonies on peach and could either be their descendants or migrants from outside the immediate area.

Taylor (1977) presents evidence that Watson’s (1966) success in forecasting sugar beet yellowing viruses for several British sugar beet areas from the weather at Rothamsted is possible because of the position of Rothamsted between the source of early GPA migrants from overwintering areas, and the sugar beet grow- ing areas. This implies that Jordan and Harrow, where the GPA overwinters on peach, are suitable areas for GPA monitoring related to virus epidemiology and should be relevant for such research in future years, although the difference is that early migrants in Britain are principally alienicolae from weed and crop hosts (Woodford and Lerman 1977).

Acknowledgments

We are grateful for assistance from P. A. High and J. D. Richardson and student assistants during 1970-76.

References

ELLiotT, W. M. 1971. Annual flight patterns of the green peach aphid Myzus persicae (Homoptera: Aphididae). Can. Ent. 103: 1157-1163.

FISHER, K. H. 1976. Orchard information. Essex-Kent counties Circular 6-76. Ontario Ministry of Agriculture and Food.

HILLE Ris LAMBERsS, D. 1955. Potato aphids and virus diseases in the Netherlands. Ann. appl. Biol. 42: 355-360.

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Proceedings of the Entomological Society of Ontario Volume 110, 1979

JOHNSON, C. G. 1950. The comparison of suction trap, sticky trap and tow-net for the quanti- tative sampling of small airborne insects. Ann. appl. Biol. 37: 268-285.

Kemp, W. G. and P. A. Troup. 1978. A weather index to forecast potential incidence of aphid-transmitted virus diseases of pepper in the Niagara Peninsula. Can. J. Plant Sci. 58: 1025-1028.

MACGILLIvRAY, M. E. 1977. Trap monitoring program for alate aphids. Research Summary 1977. Research Station, Fredericton, N.B. : 36-37.

RICHARDS, W. R. 1964. A short method of making balsam mounts of aphids and scale insects. Can. Ent. 96: 963-966.

RoBERT, Y. 1976. Activité saisonniére de vol des pucerons (Hom. Aphididae) dans l’ouest de la France. Résultates de neuf années de piégeage (1967-1975). Ann. Soc. ent. Fr. (N.S.) 12: 671-690.

Tay Lor, L. R. 1977. Migration and the spatial dynamics of an aphid Myzus persicae. J. Anim. Ecol. 46: 411-423.

Taylor, L. R. and R. A. FRENCH. 1978. Rothamsted insect survey, ninth annual summary. Rep. Rothamsted exp. stn. (1977) part 2: 79-112.

WATSON, M. A. 1966. The relation of annual incidence of beet yellowing viruses in sugar beet to variations in weather. Plant Path. 15: 145-9.

WEINTRAUB, M. 1977. Research Branch Report 1976. Research Station, Vancouver, B.C. : 7.

WoopForD, J. A. T. and P. M. LERMAN. 1977. The effect of genotype, environment, age and morph on morphological variation in alate Myzus persicae (Sulzer) (Hemiptera: Aphi- didae). Bull. ent. Res. 67: 685-693.

(Received 11 June 1979)

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Proceedings of the Entomological Society of Ontario Volume 110, 1979

EFFECT OF PERMETHRIN, CYPERMETHRIN AND CHLORPYRIFOS ON LOUSE POPULATIONS OF BEEF CATTLE

D. J. MADDER and G. A. SURGEONER Department of Environmental Biology, University of Guelph, Guelph, Ontario NIG 2W1

Abstract Proc. ent. Soc. Ont. 110: 29-34 (1979)

The following insecticides were evaluated for louse control: permethrin as a dust at 142 and 284 mg active ingredient (ai)/animal and as a spray at ca. 100 and 200 mg ai/animal, cypermethrin as a pour-on at 375 mg ai/animal, and chlor- pyrifos as a spot-on at 20 mg/kg. Louse populations were primarily Bovicola bovis (L.) (>90%) and low numbers of Linognathus vituli (L.) and Haemato- pinus eurysternus (Nitzsch). All treatments initially reduced populations, but they recovered after the permethrin 142 mg ai/animal dust and both spray applications so as to warrant retreatment. The permethrin 284 mg ai/animal dust, cyper- methrin and chlorpyrifos treatments all effectively reduced populations for at least 49 days after treatment.

Introduction

Cattle lice of economic importance in Canada include the short-nosed cattle louse, Haematopinus eurysternus (Nitzsch); long-nosed cattle louse, Linognathus vituli (L.); cappillate louse, Solenopotes capillatus Endulein; and the cattle biting louse, Bovicola bovis (L.). In Ontario, Teskey (1960) reported that lice were present on 43 of 70 herds examined with B. bovis the most abundant followed by L. vituli, S. capillatus and H. eurysternus.

Lice have been reported as major pests of cattle causing low vitality, reduced growth and constant irritation (Matthysse 1946; Kemper et al. 1948). Recent studies (Collins and Dewhirst 1965; Rich 1966; Cummins and Tweedle 1977) have indicated that natural louse populations rarely attain levels that cause economic losses. Despite this, many producers in Ontario treat all their cattle to ease the irritation and prevent potential weight gain reductions caused by lice.

Populations of lice attain maximum levels during mid-winter in temperate North America resulting in the initiation of control measures in January or Febru- ary (Wright 1976). Products currently recommended for control in Ontario often require two applications about two weeks apart (Anonymous 1979). The second application is required because most insecticides neither affect louse eggs nor have sufficient residual activity to destroy newly emerged nymphs which may hatch 7-10 days after the initial treatment. These nymphs are a source of reinfestation and require a second treatment before new eggs are laid. A control measure requiring only one treatment would increase convenience and decrease cost.

The study reported herein was undertaken to determine; a), the efficacy of permethrin, cypermethrin, and a new formulation of chlorpyrifos for louse control; and b), the number and type of applications for the most efficient control. Weight gains of treated and control animals were also monitored.

Materials and Methods

Animals used were bull calves and heifers of mixed crossbreeds weighing 200 to 400 kg. All harbored natural louse populations and had no prior history of insecticidal treatment. Animals were maintained on a large feedlot near Guelph, Ontario and were individually identified by numbered ear tags.

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Proceedings of the Entomological Society of Ontario Volume 110, 1979

The insecticides, formulations, application rates and number of animals treat- ed are presented in Table I. Application rates were those recommended by the manufacturers. Treatments for tests one to three were performed on 9 January 1979 while treatments for tests four to seven were performed on 16 January 1979. Dust formulations were individually weighed and then shaken onto both sides and backline of the cattle. The permethrin spray was mixed from a 25% active ingre-

TABLE I. Insecticides evaluated and dosages applied for control of cattle lice, Guelph, Ontario, 1979.

Number Test Application Rate (ai)* of Cattle Insecticide Number Formulation 1st Treatment 2nd Treatment Treated Permethrin 1 WL 43479 284 mg/animal not required 8 0.25% ai dust* ji Ectiban® 142 mg/animal 142 mg/animal 8 0.25% ai dust 3 Ectiban® 100 mg/animal 200 mg/animal 7 0.0125% ai spray Cypermethrin 4 WL 43467 375 mg/animal not required 7 0.25% ai pour-on‘* Chlorpyrifos 5 Dursban®44 20 mg/kg not required 8 43.2% ai spot-on* 6 Dursban®44 20 mg/kg not required 3(1)° 43.2% al spot-on* iL Dursban®44 20 mg/kg not required 2(Q) 2 43.2% ai spot-on*

* Active ingredient.

» Number in parentheses refers to the number of non-treated cattle kept in the same pen as the treated cattle.

© Shell Canada Ltd.

ICI Americas Ltd.

* Dow Chemical of Canada Ltd.

i)

dient (ai) emulsifiable concentrate (EC) and water, and applied to wet the entire animal using a Chapman R #135 compressed air sprayer. The mean volume of spray applied to each animal was 0.8 | for the first treatment and 1.6 | for the second treatment. The application rate was doubled for the second treatment in an attenipt to increase efficacy. Cattle in tests two and three were retreated 35 and 21 days posttreatment respectively when louse numbers began to increase signifi- cantly. The cypermethrin pour-on was mixed from a 10% ai EC and water, and applied along the backline. The chlorpyrifos (43,2% ai) ready-to-use spot treat- ment was applied to the centre of the backline using a plastic squeeze applicator.

Cattle in tests one to four were held in a heated barn with three or four animals per pen. All cattle in each pen received the same treatment. Plywood on the sides of the pens prevented physical contact between treated animals. Ten

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Proceedings of the Entomological Society of Ontario Volume 110, 1979

control animals were held in the same barn with a vacant pen between treated groups and the controls. The same cattle were used as controls for tests one to four, however, due to the one week delay in initiation of test four, louse indices of control animals for test four were not made on the same date as those for tests one to three. All cattle were fed a full ration diet of 70% corn silage, 27% cob meal, 2.5% soybean and 0.5% mineral supplement.

Cattle used in tests five to seven were held in unheated, open-faced barns with four animals per pen. All treated animals were heifers with eight bull calves located in another barn but under the same conditions used as controls. Heifers were fed as in treatments one to four, while bull calves were fed 50% corn silage and 50% pelleted ration containing 13% protein. In tests six and seven untreated animals were held with chlorpyrifos treated cattle to determine if all animals in a herd had to be treated to provide adequate control throughout the herd. Only untreated cattle in tests six and seven were weighed and assayed for lice. Louse numbers on treated animals in tests six and seven were assumed to respond simi- larly to those of chlorpyrifos treatment five.

Louse populations were monitored using a louse index based on the total number of lice found in 52 hair-parts (ca. 3 cm long) per animal (Shemanchuk et al. 1963). The 52 hair-parts were distributed as follows: three tail head, six backline, six side, two ear and six brisket on each side of the animal and six along the crest of the neck. Each animal was held in a squeeze and counts done imme- diately before treatment and at 7, 21, 35 and 49 days posttreatment except that the 35 day posttreatment counts for tests five to seven were not performed. Cattle were weighed to the nearest kg prior to each louse assessment.

The average weight gain per animal per day over the entire study period was used as the data for a one-way analysis of variance. Statistical analyses were not performed on tests six and seven due to insufficient sample size. A modified Abbott’s formula was used to determine the percent reduction of louse populations resulting from treatments (Henderson and Tilton 1955).

Results and Discussion

Three species of lice were found on the cattle: B. bovis, L. vituli and H. eurysternus. B. bovis comprised >90% of the lice with the greatest densities (>70 lice/hair-part) along the crest of the neck and backline. H. eurysternus and L. vituli were most common along the brisket with maximum densities of ca. 10 lice/hair-part. The lowest densities of lice were along sides and tail heads.

Populations of lice on the control animals (Table II) for tests one to four attained maximum numbers between 14 and 21 days after the initiation of the first tests (late January) and declined thereafter. Louse populations on the control cattle for tests five to seven declined steadily throughout the experiment. The increase in lice in mid-winter and subsequent decline is typical of louse populations although the cause of these fluctuations is not fully understood. Jensen and Roberts (1966) attributed S. capillatus population fluctuations to be dependent upon air temperatures while Lewis et al. (1967) attributed major fluctuations to host grooming.

Permethrin Tests

The permethrin treatments initially reduced louse numbers by 85 to 95%. The lice remaining seven days posttreatment in tests one and two were primarily L. vituli and some H. eurysternus located on the brisket. The survival of these lice

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Proceedings of the Entomological Society of Ontario Volume 110, 1979

was probably due to insufficient dust reaching the brisket. Test three initially reduced the numbers of lice over the entire body, including the brisket. However, populations subsequently increased, apparently due to recruitment from B. bovis eges located along the crest of the neck. As a result of the significant increase in tests two and three, animals were retreated 35 and 21 days posttreatment respec-

tively. These retreatments again initially reduced populations but they increased rapidly again in test three.

The most efficient and effective of the permethrin treatments was test one (284 mg 0.25% ai dust/animal), requiring only one treatment to produce >95%

TABLE II. Effect of permethrin (tests 1 to 3) cypermethrin (test 4) and chlorpyrifos (tests $ to 7) on louse populations and weight gains in cattle, Guelph, Ontario, 1979.

Mean Test Mean Louse Index Days Posttreatment Weight Gain Number 0 7 21 35 49 (kg/animal/day)

1 190.8 9.5 15sl 5207 17.6 1.06 (21.6)? (4.2) (5.4) (9.4) (VD) (0.07)

2 222.0 9.1 47.8 63.0” 3.1 ital ES) (38.3) (355) (9.6) (3:3) G9) (0.06)

3 IS Bee 24.8 Sal 15.4 63.6 112 (20.3) (GlS7)) (16.3) (6.0) (35.1) (0.04)

Controls 79.6 119.8 191.4 140.3 85.5 1e1S (tests 1-3) (11.5) (16.6) (Bit) G19) (14.7) (0.05) 4 DS 0 1.4 233 7.0 0.95 GID) (—) (1.0) (1.2) (5.6) (0.09)

Controls 119.8 DISD 224.1 106.2 61.4 1.16 (test 4) (16.6) (48.4) (38.3) (19.4) (24.4) (0.05) 5) 120.1 0 0 NCS 0 1.14 (30.9) (—) (=) (==) (0.08)

6 112.0 0 0 NC* 0 1.06 ()) (—) (—) (—) (=)

a 180.0 0 0 ING> 0 eat7, (119) (—) Cc) Ge) (On)

Controls 69.6 55.0 61.8 NCS 32.6 E27 (tests 5-7) GON) (14.6) (18.3) (6.9) (0.11)

* All bracketed numbers are standard errors. » Retreated immediately after count. © Not counted.

reductions throughout the experiment. This residual efficacy was due to either a direct ovicidal action, or residual contact toxicity to first-instar nymphs shortly after hatching. Test two was less efficient requiring two treatments and, because of the lower application rate, had little residual efficacy. Test three was the least efficient and effective requiring two spray applications with little residual efficacy even after the second treatment at the higher rate. In addition, most producers

would be adverse to soaking their animals in mid-winter if other materials were available.

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Proceedings of the Entomological Society of Ontario Volume 110, 1979

Cypermethrin Tests

The cypermethrin treatment caused a 100% reduction in lice seven days post- treatment with only slight recovery by the end of the experiment. Those lice present after treatment were mainly L. vituli and a few H. eurysternus located on the brisket. The residual efficacy may be due to ovicidal action, residual contact or systemic toxicity.

Chlorpyrifos Tests

The chlorpyrifos treatment (test five) caused a 100% reduction in louse numbers with no recovery. This residual efficacy was similar to that reported by Buchanan and Coles (1971) and Loomis et al. (1976) in New Zealand who used spray and spot-on chlorpyrifos formulations against L. vituli. Both studies reported that the residual efficacy was due to an ovicidal effect that eliminated reinfestation from hatching eggs.

Tests six and seven showed 100% reductions in louse populations on the untreated cattle when held with treated animals. This transfer of insecticide between cattle may have been from rubbing and/or a fumigant action. A similar phenomenon suggestive of fumigant action has been reported for Haematopinus suis (L.) (Surgeoner in press). The fact that not all animals need be treated may result in substantial savings in time and money required for louse control. These data indicate that the spot-on formulation of chlorpyrifos is efficient and effective requiring one application to produce 100% residual efficacy with neither mixing nor significant wetting of the cattle required.

Effect on Weight Gain

Although these trials were designed to evaluate the efficacy of insecticides, mean daily weight gains of cattle in the trials were also determined (Table II). The weight gain data are confounded as animals of both sexes were used, rations for some controls were different and housing conditions varied. Recognizing these variables, it should be noted that statistical analyses showed no significant differ- ences between weight gains of treated and untreated animals.

Acknowledgments

The authors wish to thank ICI Americas Inc., Shell Canada Ltd. and Dow Chemical of Canada Ltd. for the supply of insecticides and grants in-aide. Assist- ance from personnel of the Elora Beef Cattle Research Station, Ontario Ministry of Agriculture and Food and technical assistance of B. Beattie and S. Smith of the University of Guelph is also gratefully acknowledged. Financial assistance from the Ontario Ministry of Agriculture and Food is also gratefully acknowledged.

References

ANONYMOUS. 1979. Fly and louse control on beef cattle. Agdex 420/653. Ontario Ministry of Agriculture and Food.

BES NAN, R. S. and P. G. Coles. 1971. Control of lice on cattle with Dursban. N.Z. Vet. J. : 197-202.

CoLLINs, R. C. and L. W. DEwuirsT. 1965. Some effects of the sucking louse, Haematopinus eurysternus, on unsupplemented range cattle. J. Am. Vet. Med. Assoc. 146: 129-132.

CuMmMINsS, L. J. and N. E. TWEEDLE. 1977. The influence of light infestations of Linognathus vituli on the growth of young cattle. Aust. vet. J. 53: 591-592.

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HENDERSON, C. T. and E. W. TILTON. 1955. Tests with acaricides against brown wheat mite. J. econ. Ent. 48: 157-161.

JENSEN, R. E. and J. E. ROBERTS. 1966. A model relating microhabitat temperatures to seasonal changes in the little blue louse (Solenopotes capillatus) population. Georgia Agric. Exp. Sta. Tech. Bull. 55. 22 pp.

KEMPER, H. E., N. G. CorBETT, J. H. ROBERTS and H. O. PETERSON. 1948. DDT emulsions for the destruction of lice on cattle, sheep and goats. Am. J. vet. Res. 9: 373-378.

Lewis, L. F., D. M. CHRISTENSON and W. Eppy. 1967. Rearing the long-nosed cattle louse and cattle biting louse on host animals in Oregon. J. econ. Ent. 60: 755-757.

Loomis, E. C., A. N. WEBSTER and P. G. Loss. 1976. Trials with chlorpyrifos (Dursban) as a systemic insecticide against the cattle louse. Vet. Rec. 98: 168-170.

MatTTuyssE, J. G. 1946. Cattle lice, their biology and control. Cornell Univ. Agric. Expt. Sta. Bull. 832. 67 pp.

RicH, G. B. 1966. Pour-on systemic insecticides for the protection of calves from Linognathus vituli. Can. J. Anim. Sci. 46: 125-131.

SHEMANCHUK, J. A., W. O. HAUFE and C. O. M. THOMPSON. 1963. Effects of some insecti- cides on infestations of the short-nosed cattle louse. Can. J. Anim. Sci. 43: 56-64.

SURGEONER, G. A. Evidence of ovicidal activity by fumigant action using chlorpyrifos for control of Haematopinus suis (L.) Anoplura, Haematopinidae. Proc. ent. Soc. Ont. (in press).

TESKEY, H. J. 1960. Survey of insects affecting livestock in southwestern Ontario. Can. Ent. 92: 531-544.

WRIGHT, R. E. 1976. Efficacy of Ronnel as a pour-on and Coumaphos as a dust for control of cattle lice. Can. Ent. 108: 83-88.

(Received 1 May 1980)

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DISTRIBUTION OF MICROCTONUS AETHIOPOIDES, A PARASITOID OF THE ALFALFA WEEVIL (COLEOPTERA: CURCULIONIDAE) IN ONTARIO’

D. G. Harcourt’, C. R. EL.is’, and J. C. GUPPY’

Abstract Proc. ent. Soc. Ont. 110: 35-39 (1979)

Microctonus aethiopoides Loan, a bivoltine European parasitoid of the adult alfalfa weevil, Hypera postica (Gyll.), has become established throughout south- ern Ontario. A detailed survey of 41 counties in 1979 showed that incidence of parasitism caused by the spring generation of M. aethiopoides ranged from 13 to 92% and averaged 60. Dispersal in Ontario has been the result of recolonization from the United States. Reasons for its more rapid natural spread in Ontario are postulated.

Introduction

The braconid Microctonus aethiopoides Loan is a potentially important biological control agent of the alfalfa weevil, Hypera postica (Gyll.), in Ontario. Unlike other parasitoids of the weevil, this species attacks the adult stage. Hence, it enjoys a distinct advantage in that it is not forced to compete directly with Entomophthora phytonomi Arthur, a highly contagious disease organism that kills the weevil larvae and cocooned stages during recurrent epizootics (Harcourt et al. PO7491977 )

M. aethiopoides has two generations a year (Abu and Ellis 1976). The adults of the first brood attack the overwintered weevils in the spring during the period of oviposition. Those of the second brood attack the new generation of adults in the summer before they leave the field. Both sexes are sterilized and subsequently killed by the parasitoid when it emerges. The second generation of the parasitoid passes the winter as an immature larva inside the hibernating host. Its general biology has been outlined by several authors, e.g., Loan and Holdaway 1961, Neal and Bickley 1971, Van Driesche and Gyrisco 1979.

Of European origin, M. aethiopoides was first introduced into the eastern United States in 1957 and 4 years later was firmly established in New Jersey (Day et al. 1971). Through successive recolonization and natural dispersal, the braconid is now present in at least 14 eastern states (Dysart and Day 1976).

M. aethiopoides was first released in Ontario in 1970 and 1971 (Williamson 1971, 1972) and recoveries were made one or two years later at five widely separated points across the Province (Dysart and Day 1976). Surveys in 1973 and 1974 by Abu and Ellis (1976) suggested that the parasitoid was slow to spread but in 1975 intensive sampling at two release sites by these same authors revealed high levels of parasitism. In long-term study plots in the Bay of Quinte area, its impact was felt for the first time in 1978 when populations of summer

‘Contribution from the Ottawa Research Station (No. 596) of the University of Guelph. This research was supported in part by the Ontario Ministry of Agriculture and Food.

"Ottawa Research Station, Agriculture Canada, Ottawa, Ontario. “Department of Environmental Biology, University of Guelph, Guelph, Ontario.

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adult weevils were heavily attacked. This and numerous inquiries from extension personnel prompted us to determine the distribution of M. aethiopoides in south- ern Ontario.

Materials and Methods

During the spring of 1979, overwintered weevils subject to attack by adults of the first brood were collected from alfalfa fields in each county of southern Ontario. To ensure that larval stages of the parasitoid were present, samples from all areas were collected between 140 and 170°D >9°C. Sampling began in south- western Ontario on May 28 and was completed progressively later across the Province. The samples were taken with a standard 38 cm sweepnet and 200 to 1000 sweeps, each consisting of a single sweep of the net through approximately 180°, were taken at each of 85 locations in 41 counties. As a rule, 2 sites were sampled per county (Fig. 1).

The adult weevils were taken to the laboratory, placed in cages on a screened platform (Loan and Holdaway 1961), and held for a minimum of 4 weeks. Emerging larvae dropped through the mesh and pupated in a layer of glass wool.

Results and Discussion

A total of 4,617 weevils were taken in 35,000 sweeps and numbers/100 sweeps ranged from 0.2 to 78. Table I shows that the parasitoid was present in every county and at all sites sampled. Incidence of attack ranged from 13 to 92%, averaging 60.

These levels of parasitism are comparable to those reported for the spring generation of M. aethiopoides in the northeastern United States (Brunson and Coles 1968, Dysart and Day 1976, Van Driesche and Gyrisco 1979). However, in Ontario levels of parasitism for the summer generation have generally been higher (Abu and Ellis 1976, Harcourt and Guppy unpublished). In the north- eastern U.S. the adult weevils move from the field to aestivate soon after emer- gence from their cocoons (Blickenstaff et al. 1972). However, in Ontario dispersal from the field is delayed by cooler weather (Surgeoner and Ellis 1976) and in some years the weevils remain to feed for a considerable length of time. In eastern Ontario this period can extend for up to 6 weeks. This delay effectively increases the exposure time to the parasitoid and improves the chances of its survival. Furthermore, delayed dispersal and subsequent higher levels of parasitism would tend to enhance its rate of spread since the host weevil disperses freely before and after hibernation.

It is too early to judge what impact M. aethiopoides will have on population trends of H. postica in Ontario. Previous to 1978, numbers of the weevil oscillated under control of the fungus disease about a level close to the economic threshold. However, this organism is not entirely compensating in its action and periodic population eruptions, mostly of a local nature, have occurred each year. It is hoped that M. aethiopoides will damp these oscillations by killing a significant proportion of those individuals that escape disease in the larval and cocooned stages.

References

Abu, J. F., and C. R. ELLs. 1976. Biology of Microctonus aethiopoides, a parasite of the alfalfa weevil, Hypera postica, in Ontario. Environ. Ent. 5: 1040-42.

BLICKENSTAFF, C. C., J. L. HUGGANS, and R. W. SCHRODER. 1972. Biology and ecology of the alfalfa weevil, Hypera postica in Maryland and New Jersey, 1961 to 1967. Ann. ent. Soc. Am. 65: 336-49.

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LAKE HURON

2 LAMBTON 1

PARRY SOUND

HALIBURTON

GEORGIAN BAY

a % % 3

Ss %

LAKE ONTARIO

KILOMETERS

FicurE 1. Sampling sites for M. aethiopoides in southern Ontario, 1979.

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TABLE I. Parasitism of the alfalfa weevil in Ontario by the first generation of M. aethiopoides, 1979.

County Site % Parasitism County Site % Parasitism Brant 1 58.3 Lennox & Addington 1 TQ 2 12.9 D 91.7 Bruce 1 18.8 Lincoln 1 51.8 7 Sali Middlesex 1 59.4 Carleton 1 66.7 Norfolk 1 5328 D2 68.6 2 80.1 Dufferin i 90.0 Northumberland 1 43.3 DD 45.4 72 77.8 Dundas 1 33.3 3 Peal! D 54.5 Oxford 1 80.0 Durham 1 87.0 2 58.1 yD 65.0 Peel 1 31.6 Elgin 1 43.8 2 44.7 Dy 44.4 Perth 1 25.4 Essex 1 75.0 yD) 49.0 2 50.0 Peterborough 1 60.8 Frontenac 1 50.0 yD 70.0 2 80.0 Prescott 1 63.3 Grey 1 ye7/ D 68.0 2 2S Prince Edward 1 80.0 Glengarry 1 60.0 2 86.4 2 45.1 Renfrew 1 75.0 Grenville 1 TZ 2 595 2 55.0 Russell 1 60.0 Haldimand 1 36.7 2, 73.9 2 50.7 Simcoe 1 69.6 Halton 1 qs oD 38.0 2 86.9 3 53.8 Hastings 1 83.8 4 49.8 2 77.4 5 56.2 3 78.9 Stormont 1 38.9 4 91.7 2 44.0 Huron 1 37.8 Victoria 1 73.5 2 33.3 2: 66.6 Kent 1 63.2 Waterloo 1 19.3 2 40.0 Welland 1 57.5 Lambton 1 71.4 y 66.7 2 61.5 Wellington 1 69.2 Lanark 1 59.2 2 TAS 2 62.5 Wentworth 1 83.3 Leeds 1 56.0 2 65.5 2 56.6 York 1 86.2 2 81.7

BRUNSON, M. H., and L. W. CoLes. 1968. The introduction, release, and recovery of parasites of the alfalfa weevil in eastern United States. U.S. Dep. Agric., Production Res. Rep. 101. 12 pp.

Day, W. H., L. W. Coes, J. A. STEWART, and R. W. FUESTER. 1971. Distribution of Microc- tonus aethiops and M. colesi, parasites of the alfalfa weevil, in the eastern United States. J. econ. Ent. 64: 190-93.

DysarT, R. J., and W. H. Day. 1976. Release and recovery of introduced parasites of the alfalfa weevil in eastern North America. U.S. Dep. Agric. Production Res. Rep. 167. 61 pp.

Harcourt, D. G., J. C. Guppy, D. M. MacLeop, and D. TyrrELL. 1974. The fungus Entomophthora phytonomi pathogenic to the alfalfa weevil, Hypera postica. Can. Ent. 106: 1295-300.

Harcourt, D. G., J. C. Guppy, and M. R. BINNS. 1977. The analysis of intrageneration change in eastern Ontario populations of the alfalfa weevil, Hypera postica (Coleoptera: Curculionidae). Can. Ent. 109: 1521-34.

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Loan, C., and F. G. HoLtpAway. 1961. Microctonus aethiops (Nees) auctt. and Perilitus rutilus (Nees) (Hymenoptera: Braconidae), European parasites of Sitona weevils (Coleoptera: Curculionidae). Can. Ent. 93: 1057-79.

NEAL, J. W., Jr., and W. E. BicKLey. 1971. A study of Microctonus aethiops (Nees), a braconid parasite of the alfalfa weevil, Hypera postica (Gyllenhal). Univ. Md. Agric. Exp. Stn. Sci. Art. 1668. 61 pp.

SURGEONER, G. A., and C. R. ELLis. 1976. Effect of field applications of carbofuran on Hypera postica (Coleoptera: Curculionidae) and its parasitoids. Can. Ent. 108: 649-54.

VAN DRIESCHE, R. G., and G. G. Gyrisco. 1979. Field studies of Microctonus aethiopoides, a parasite of the adult alfalfa weevil, Hypera postica, in New York. Environ. Ent. 8: 238-44.

WILLIAMSON, G. D. 1971. Insect liberations in Canada, 1970. Parasites and predators. Can. Agric. Lib. Bull. 34. 16 pp.

WILLIAMSON, G. D. 1972. Insect liberations in Canada, 1971. Parasites and predators. Can. Agric. Lib. Bull. 35: 16 pp.

(Received 12 December 1979)

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THE POTATO LEAFHOPPER, EMPOASCA FABAE (HOMOPTERA: CICADELLIDAE)

AND OTHER PESTS OF PEANUTS IN ONTARIO

C. R. ELLis and R. C. Roy University of Guelph, Guelph, Ontario N1G 2W1

Abstract Proc. ent. Soc. Ont. 110: 41-45 (1979)

Observations on peanuts in Ontario over a ten-year period showed that the potato leafhopper, Empoasca fabae (Harris), was the most consistent and important pest. The cutworms, Euxoa messoria (Harris) and Peridroma saucia (Hubner), were sometimes present and will occasionally require control. The tobacco thrips, Frankliniella fusca (Hinds) was not found and neither thrips nor aphids were important.

Introduction

Research was initiated in Ontario in 1970 to explore peanuts as an alternative crop on the sandy, tobacco lands of the Delhi area of southwestern Ontario. Early results were promising and the program was expanded in 1974 under the New Crop Development Fund of Agriculture Canada. Some pest problems were evident and in preparation for commercial production it became essential to identify insect pests as a first step towards obtaining efficacy data to support the Canadian registration of effective insecticides where necessary. Reported here are observa- tions on pests of Spanish and Valencia peanuts in Ontario over the 10-year period from 1970 to 1979.

Potato leafhopper, Empoasca fabae (Harris)

The most consistent and important pest every year was the potato leafhopper. Adults of this pest disperse into Ontario from the south each year and can be collected from various crops by the first week of June. These migrants colonized the peanuts and significant populations of nymphs were present by early July; 15/plant July 12, 1976, 8/plant July 13, 1977 and 13/plant July 12, 1978. In non-treated peanuts the population often reached 40 nymphs/plant in late July or early August. The numbers of adults swept from non-sprayed Spanish peanuts on three farms in 1978 are shown in Fig. 1. The initial influx_of migrant adults was typically followed by declining numbers until the second week of July when recruitment of first generation adults swelled the population to as many as 16 adults/sweep. A second peak began the last week of August as the peanuts were maturing and was not of significance.

Feeding by the potato leafhopper caused chlorosis of the leaves (Fig. 2C) followed by necrosis at the tip and margins of the leaves, a condition known as hopperburn (Fig. 2D), and this contributed to leaflet drop at the base of the plants (Fig. 2F). These symptoms became noticeable every year by July and indicated a pest problem requiring chemical control and, in fact, all the peanuts used in agronomic experiments were routinely protected by planting time treat- ments with systemic insecticide (carbofuran or aldicarb) and/or by foliar sprays of carbary].

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The potato leafhopper has been described as an important pest of peanuts in Virginia (Poos et al. 1947) and chemical controls are registered for this pest in the U.S.A. The efficacy of various chemical controls and the significance of these populations are discussed elsewhere.

120

ADULTS 25 SWEEPS

89

JUNE JULY AUG.

FIGURE 1. The seasonal abundance of adult potato leafhoppers on non-treated peanuts on three farms near Delhi, Ont., 1978.

In addition to chlorosis and hopperburn, an influx of adult leafhoppers was often associated with the presence of single wilted leaves on the tops of the plants (Fig. 2G). These flaccid leaves were more prevalent during times of moisture stress such as dry periods and in the mid-afternoon. That this symptom was related to the presence of adult potato leafhoppers was confirmed in field cages. These cages, 45 x 60 x 82 cm, each enclosed five peanut plants and were infested with from zero to six adult leafhoppers on July 5. Six days later on July 11, all of the cages with six leafhoppers contained “wilted leaves” whereas this symptom was absent in all the controls. The symptom was still appearing in the infested cages after eight days and by that time some of the leaves that were wilted earlier were reduced to a petiole stub without leaflets. A large influx of leafhoppers from July 7 to 13, 1977 resulted in the most noticeable symptoms during the years of this study. There is no evidence that E. fabae is a vector of viruses (Nielson 1968), and the cause of the wilting is not known.

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A second species of leafhopper became numerous in one area of non-sprayed peanuts near Delhi, Ontario the second week of July, 1978. This species was identified by Dr. K. G. A. Hamilton of the Biosystemics Research Institute, Ottawa as of Amplicephalus inimica (Say), the painted leafhopper. In no other instance was this species noticed on peanuts and it probably dispersed from surrounding

FIGURE 2. Foliar injury to peanuts at Delhi, Ont.; A, leaf removal by groundhogs; B, leaves chewed by cutworms, Peridroma saucia (Hubner); C and D, leaf injury by the potato leaf- hopper, C, chlorosis, and D, tip necrosis; E, cowpea aphids; F, basal leaf drop; G, wilted leaves associated with presence of potato leafhoppers.

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fields of weeds. Macrosteles fascifrons (Stal), the aster leafhopper, was collected as adults at densities of less than one per sweep from most unsprayed peanut fields in June and early July but also is not considered a pest of peanuts.

Cutworms

The dark-sided cutworm, Euxoa messoria (Harris), attacks a number of crops in southwestern Ontario and is a serious pest of tobacco (Cheng 1971, 73). This species occasionally injured peanuts by pruning leaves but some cutworms could be supported on peanuts without plant mortality. Rye is the preferred host for Oviposition in the fall and the first three instars feed on the rye until it is plowed under or broken down (Cheng 1971). Problems are most likely to be located where dark-sided cutworms have dispersed from rye into adjacent peanuts or possibly where a rye rotation crop has been plowed under.

Some field cages that covered unsprayed peanuts in 1977 were naturally infested with cutworms. Five of the 48 cages contained cutworms and damage was noticeable by July 11 (Fig. 2B). Some of the larvae were reared to adults and the identification confirmed by Dr. E. W. Rockburne of BRI, Ottawa, as the variegat- ed cutworm, Peridroma saucia (Hubner). This species is common in southwestern Ontario and periodically damages vegetable and field crops in the early season and is of most concern in mid-summer (Harris et al. 1977).

Thrips

The tobacco thrips, Frankliniella fusca (Hinds), causes its main visible injury to the developing leaflets and flower buds (Poos 1945). Although the effects of this injury on yield have been inconsistent (Smith 1972), insecticides are recom- mended in the USA for thrips control and there has been a program to develop host resistance. The tobacco thrips is present in Ontario but of minor interest and no controls are recommended for thrips on Ontario tobacco (Ontario Ministry of Asriculture and Food 1979). Plants with crinkled leaves and suspected of having thrips were examined during the period 1976-78. Thrips were rare and those few specimens collected from peanuts were identified by Dr. B. S. Heming of the University of Alberta as F. tritici (Fitch), the flower thrips. This species is com- mon on many plants but is not a pest of peanuts. Thrips should not be a problem on peanuts in Ontario.

Aphids

Although various alate aphids were found on peanuts in Ontario, in only one instance did colonization occur (Fig. 2E). Unfortunately the specimens were lost before identification could be confirmed. The species was most likely the cowpea aphid, Aphis craccivora Koch., a pest of peanuts in the USA and, although not reported from Ontario, present in Quebec and New York, areas that are contiguous with Ontario (Smith and Parron 1978). No problems are anticipated with aphids on Ontario peanuts.

Groundhogs

In checking for injury by leaf-feeding insects, the most common injury seen was that caused by groundhogs (Fig. 1A). The sandy soils being investigated for peanut production dried out quickly and the lush green peanut growth was an attractive food for groundhogs with burrows in banks and bush along field mar-

AA

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gins. The leaf removal on the tops of the plants (Fig. 1A) was easily distinguished from the leaf drop at the base of the plants associated with leafhoppers or other stress (Fig. 1F).

Acknowledgments

We thank Brian Beattie, Peter White and Godfrey Chu for valuable assistance in maintaining plots and in sampling. This research was supported in part by a New Crop Development Fund from Agriculture Canada and in part by the Ontario Ministry of Agriculture and Food.

References

CHENG, H. H. 1971. Assessment of tobacco losses caused by the dark-sided cutworm, Euxoa messoria (Lepidoptera: Noctuidae), Delhi, Ontario. Can. Ent. 103: 534-41.

CHENG, H. H. 1973. Observations on the bionomics of the dark-sided cutworm, Euxoa messoria (Lepidoptera: Noctuidae), in Ontario. Can. Ent. 105: 311-22.

Harris, C. R., H. J. SvEc and R. A. CHAPMAN. 1977. The effectiveness and persistence of some insecticides used for control of the variegated cutworm attacking tomatoes in southwestern Ontario. Proc. ent. Soc. Ont. 108: 63-8.

NIELSON, M. W. 1968. The leafhopper vectors of phytopathogenic viruses (Homoptera, Cicadellidae) taxonomy, biology and virus transmission. U.S. Dep. Agric. Tech. Bull. No. 1382. 386 pp.

ONTARIO MINISTRY OF AGRICULTURE AND Foop. 1979. Tobacco Production Recommendations. OMAF, Pub. 298. 44 pp.

Poos, F. W. 1945. Control of tobacco thrips on seedling peanuts. J. econ. Ent. 38: 446-8.

Poos, F. W., J. M. GRAYSON and E. T. BATTEN. 1947. Insecticides to control tobacco thrips and potato leafhopper on peanuts. J. econ. Ent. 40: 900-5.

SMITH, C. F. and C. S. PARRON. 1978. An annotated list of aphididae (Homoptera) of North America. North Carolina Agric. Expt. Sta. Tech. Bull. No. 255. 20 pp.

SMITH, J. C. 1972. Tobacco thrips-nematode control in Virginia-type peanuts. J. econ. Ent. 65: 1700-3.

(Received 3 January 1980)

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TWO NEW SPECIES OF ELAMPUS (HYMENOPTERA: CHRYSIDIDAE) FROM PUERTO RICO AND CUBA WITH NOTES ON ELAMPUS VIRIDIS CRESSON

J. T. HUBER’ and D. H. PENGELLY

Department of Environmental Biology, University of Guelph, Guelph, Ontario N1G 2W1

Abstract Proc. ent. Soc. Ont. 110: 47-51 (1979)

Two new species, Elampus puertoricensis Huber from Puerto Rico and E. cubanus Huber from Cuba, are described. The relationship of these species to other western hemisphere Elampus is discussed. E. rotundus Huber and Pengelly is newly synonymized with E. viridis Cresson. A key to species is presented.

Introduction

Only one species of Elampus, E. viridis Cresson from Cuba (Cresson 1865), has been described from the Caribbean region. Two new species are described herein, one from Puerto Rico and one from Cuba. The Puerto Rican species repre- sents the first record of the family Chrysididae from the island (Wolcott 1936, 1941).

Most of the. terminology used in this paper is the same as described in a revision of the North American Elampus (Huber and Pengelly 1977).

Key to Cuban and Puerto Rican species of Elampus

1. Apical truncation of third tergite circular or oval with a small ventral notch ACES PMI) ar he ih cases Racin nes does Matec soto e nwa cansasmonettiees set J)

— Apical truncation of third tergite crescent shaped (Fig. 6) 0... eeeeeeeeeeees EE EN ne Mc YBa Acasa cnaiand? sop balwednamodioscuseataettthecett cubanus Huber n. sp.

2. Head, thorax, and abdomen with extensive copper, gold, or red..................08 3000000008 dSonPuBeE REA IE EM AOU apt oa ed etna eden a puertoricensis Huber n. sp.

——glieads thorax, and abdOmen: GFEEM ...0.:0:06...ccadc0dsce.eheeoredeennce- viridis Cresson

Elampus puertoricensis Huber n. sp. (Figs. 1, 2, 4)

Holotype female. “Puerto Rico, Lajas, Sept.-Nov. 1960, M. Beauchamp.” (United States National Museum, Washington, D.C. Type no. 73819). Female (holotype). Length 5.4 mm. Bright green with gold and/or copper tinge or reflections on the following: scape, vertex especially in front of anterior ocellus, genae above, pronotum medially, in punctures of mesopleura and scutellum, in basal and lateral punctures of postscutellum, underside of postscutellar blade, propodeum, legs except for tarsi and apex of tibiae, posterior part of first and second tergites, third tergite except apically and along lateral margins. The copper colour is most pronounced laterally on the second tergite. Mesothorax red becom-

* Present address: Department of Entomology, University of California, Riverside, CA 92521. 47

Proceedings of the Entomological Society of Ontario Volume 110, 1979

e

: L

Pe Ohh ee holotype 2 ii 2

* 4 * [CRM Ae URN A UR UT 0.5 mm 7) EEE EEE, 0.5 mm Us 5

Ficures 1-6. 1, 2, 4, Elampus puertoricensis Huber n. sp., female. 1, face view of apical truncation of abdomen; 2, tarsal claw; 4, lateral view of fore femur. 3, 5, 6, Elampus cubanus Huber, n. sp., female. 3, tarsal claw; 5, lateral view of fore femur; 6, face view of apical truncation of abdomen showing variations.

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ing gold anteriorly between notaulices. Rims of punctures on scutellum, apex of postscutellar blade, and junction of propodeum and first tergite black. Flagellum and pedicel dark brown. Apex of tibiae and tarsi brownish-yellow. Fore wing clear basally, lightly brown-stained beyond venation. Sternites with a narrow, coppery- purple, longitudinal line medially. Lateral margins and apex of third tergite pink. Apical truncation of third tergite light brown above, dark brown below, with a dark brown rim.

Scapal basin smooth above, roughened to rugose below and laterally. Genal fringe somewhat setose, setae one ocellar-diameter in length and irregularly spaced. Pronotal punctures medium in size, densely spaced to contiguous medially. Base of fore femora below barely angular (Fig. 4). Tarsal claws with one small, vertical inner tooth (Fig. 2). First tergite smooth above basal pit with a few small, scatter- ed punctures lateral to it and mostly minute, densely to moderately spaced punc- tures along posterior margin. Second tergite with a narrow, indistinct, longitudinal smooth line medially extending about half the length of the tergite. Apical trunca- tion of third tergite oval with a very shallow ventral notch (Fig. 1).

Measurements (in mm) and ratios as follows: width/length of head 2.4; width/length of pronotum 1.7; width/length of tergites II and II 1.6, 1.6 respec- tively; width/height of apical truncation 0.50; length of flagellomeres I/II 1.7; fore wing length 3.6; stigmal length 0.33; radial sector length 0.18; distance between compound eyes 0.91; distance from median ocellus to clypeal margin 0.97; length of scape 0.44; POL 0.29;O0OL 0.26.

Male. Unknown. Biology. Unknown.

Remarks. The combination of the smooth, coppery-gold scapal basin, red and gold mesothorax, oval apical truncation with a very shallow ventral notch, and the single vertical, inner tooth in each tarsal claw separates E. puertoricensis from other Elampus.

E. puertoricensis is most closely related to E. viridis Cresson from North America and Cuba on the basis of the very short radial sector and the single, -vertical tooth in the tarsal claw. Together with E. gayi Spinola from South Amer- ica, these three species have in common a circular or oval apical truncation of the third tergite. The rather long, sparse genal fringe is unusual in that it is a male character, the females having a short, dense, setose fringe, at least in the North American Elampus.

Elampus cubanus Huber n. sp. (Fiss:)3)5,10))

Holotype female. [Cuba] ‘“Guane P. Rio, P. Alayo IX-1967. “(Biosystematics Research Institute, Ottawa).

Female (holotype). Length 4.8 mm. Green with occasional violet or blue tinge or reflections on the following: scape, scapal basin, genae, pro- and mesonotum, mesopleura. Flagellum and pedicel brown. Apex of tibiae and tarsi yellowish- brown. Fore wings tinged with brown beyond venation. Apical truncation of third tergite brown. Rims of punctures of scutellum, postscutellum, and apex of post- scutellar blade black.

Scapal basin rugose. Genal fringe short, dense, setose. Punctures on dorsum of pronotum moderately spaced medially. Base of fore femora below rounded with

49

Proceedings of the Entomological Society of Ontario Volume 110, 1979

a short, dense, setose fringe (Fig. 5). Tarsal claws with two inner teeth (Fig. 3). First tergite with minute, scattered punctures around basal pit, sparsely spaced on remainder of tergite. Second tergite with minute, densely spaced punctures. Apical truncation of third tergite crescent shaped, ventral notch less than half the height of truncation (Fig. 6).

Measurements (in mm) and ratios as follows: width/length of head 2.4; width/length of pronotum 1.9; width/length of tergites II and HI 1.3, 1.2 respec- tively; width/height of apical truncation 1.1; length of flagellomere I/II 1.6; fore wing length 3.3; stigma length 0.26; radial sector length 0.18; distance between compound eyes 0.82; distance from median ocellus to clypeal margin 0.88; length of scape 0.38; POL 0.28; OOL 0.26.

Male. Unknown. Biology. Unknown.

Paratypes: CUBA: Guane (1 2? ); Santiago de las Vegas, Habana (1 2) (University of Guelph, Guelph).

Other material examined. Baracoa (192) (United States National Museum); Guane P. Rio, IX-1967 (1¢@ ) (P. Alayo) (University of California, Davis).

Remarks. The length of three specimens (2 paratypes and specimen from Baracoa) ranged from 3.8-4.3 mm. The colour of the apical truncation of the third tergite varied from yellow to brown, and the shape varied as shown in Fig. 6. Puncation on the first tergite varied from smooth to moderate, and on the pronotum from moderate to sparse.

The combination of the rugose scapal basin and two inner teeth in each claw relates this species to E. hyalinus (Aaron) from North America. It differs from the latter by the brownish fore wings.

Alayo (1974) recorded E. viridis from Guane P. Rio and Santiago de las Vegas, Habana. These two records should be referred to E. cubanus n. sp. Possibly his other locality records should be referred to E. cubanus as well.

Elampus viridis Cresson

Elampus viridis Cresson, 1865. Proc. ent. Soc. Phil. 4: 103. Original description.

Elampus viridis: Norton, 1879. Trans. Am. ent. Soc. 7: 235. Redescription.

Elampus viridis: Provancher, 1881. Nat. Canad. 12: 303. Redescription. (?) Canadian record.

Elampus viridis: Aaron, 1885. Trans. Am. ent. Soc. 12: 219. Synonymy under Notozus marginatus Patton.

Ellampus viridis: Mocsary, 1889. Monogr. Chrysididarum. p. 78. Deserpiee quoted.

Ellampus viridis: Dalla Torre, 1892. Catalogus Hymenopterorum 4: 20. World catalogue.

Notozus viridis: Bischoff, 1913. Gen. Insectorum 151: 7. World catalogue.

Elampus viridis: Cresson, 1928. Mem. Am. ent. Soc. 5: 30. Type material.

Elampus viridis: Bodenstein, 1951. U.S. Dep. Agric., Agric. Monogr. 2: 719. Synonymy under EF. marginatus (Patton).

Elampus viridis: Alayo, 1974. Acad. Cien. Cuba. Serie Biol. 52: 12. Cuban records (= 2. cubanus n= sp»)-

Elampus rotundus Huber & Pengelly, 1977. Proc. ent. Soc. Ont. 108: 92 NEW SYNONOMY.

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Remarks. The holotype of E. viridis was examined in the Academy of Natural Sciences, Philadelphia. It is glued to a card and is in very poor condition with the head, pronotum, left wings, and part or all of four legs missing. The right fore wing and two complete legs are glued separately to the card. There is a pin hole through the mesothorax. Despite its condition three important characters vwiz., the apical truncation of the third tergite, tarsal claws, and radial sector are visible and permit the synonymy of FE. rotundus Huber and Pengelly with E. viridis to be made. The holotype is labelled as follows: “Cuba” (white label), “Type No. 2682” (red label), “3 teeth in claw” (pink handwritten label), “Elampus viridis (Type) Cresson. The specimen was almost destroyed in some way and was at first pinned” (pink handwritten label). There is, in fact, only a single tooth in each tarsal claw. A complete description and distribution in North America of this species is given (as E. rotundus) by Huber and Pengelly (1977). Since then, six specimens of E. viridis labelled “Havana, Cuba, Baker” were seen in the University of Cali- fornia, Davis. The Provancher record of FE. viridis occurring in Canada needs confirmation as his collection in Quebec City does not contain any specimens referrable to this species.

Acknowledgments

Sincere thanks are extended to the following people who allowed material of Elampus to be examined in their institutions or who provided material for study: Dr. K. V. Krombein, United States National Museum, Washington, D.C., Mrs. P. Francis, Academy of Natural Sciences, Philadelphia, and Dr. L. Kimsey, Depart- ment of Entomology, University of California, Davis. Dr. P. Alayo D., Academia de Ciencias de Cuba, Instituto de Zoologica, Havana, kindly donated specimens of E. cubanus to the University of Guelph. This work was supported, in part, by the Canada Department of Agriculture Grant 4033.

References

ALayo, P. D. 1974. Introduccion al estudio de los Himenopteros de Cuba. Superfamilia Bethyloidea. Serie Biologica No. 52. Academia de Ciencias de Cuba, Instituto de Zoologia. La Habana.

Huser, J. T., and D. H. Pengelly. 1977. A revision of the genus Elampus Spinola (Notozus duct) (Hymenoptera: Chrysididae) in America North of Mexico. Proc. ent. Soc. Ont. 08: 75-137.

Wo coTtT, G. N. 1936. “Insectae Borinquensis”. A revised annotated checklist of the insects of Puerto Rico. Puerto Rico Dep. Agric. Journal 20: 1-627.

Wo LcoTT, G. N. 1941. Supplement to “Insectae Borinquensis”. Puerto Rico Dep. Agric. Journal 25: 33-158.

(Received 28 April 1980)

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Proceedings of the Entomological Society of Ontario Volume 110, 1979

TEMPERATURE RELATIONSHIPS TO FORECAST HATCHING OF OVERWINTERED EGGS OF THE EUROPEAN RED MITE, PANONYCHUS ULMI (ACARINA: TETRANYCHIDAE)

ROBERT TROTTIER' and D. H. C. HERNE Agriculture Canada, Vineland Station, Ontario. LOR 2E0

Abstract Proc. ent. Soc. Ont. 110: 53-60 (1979)

The influence of temperature and humidity, and the importance of available moisture expressed as vapour pressure deficit on the development of overwintered eggs of European red mite, Panonychus ulmi (Koch), is described. The threshold for egg development was determined as ca. 5.6°C. Degree-day (dd) summations determined in the laboratory were field tested for their precision in predicting first and 50% hatch. Summation of 155 dd above 5.6°C after March 1 can be used to predict first hatch in the field, accurate to within one day; dd summations to 50% hatch were more variable but based on 250 dd after March 1, predicted and observed dates of 50% hatch were within three days. Biometeorological indices, based on dd summations above the temperature threshold 5.6°C, should prove useful in Integrated Pest Management programmes to forecast hatching time of overwintered P. ulmi eggs in widely different climatic areas.

Introduction

The European red mite, Panonychus ulmi (Koch), (ERM) is one of the major pests in peach and apple orchards. In southern Ontario P. ulmi has six to eight generations a year and must be controlled by acaricide treatments when mite numbers reach critical levels. In recent years, effort to reduce pesticide use in orchard ecosystems has directed our studies at Vineland Station toward develop- ment of biometeorological indices to optimize timing of pesticide applications for Laspeyresia pomonella (L.), Rhagoletis pomonella (Walsh) (Trottier, in press) and Phyllonorycter blancardella (Fab.) (Johnson, Trottier and Laing 1978). While the trend, in orchards under pest management, is to apply sprays only when ERM numbers reach critical levels, it is important to determine accurately the time of hatching of ERM overwintered eggs so that predictive models (Herne and Lund 1979) can be effective in predicting ERM critical levels during the summer. In Ontario, Herne and Trottier (1975) showed that the dates of first hatch of the ERM overwintered eggs varied greatly among the major apple growing areas, and the number of days between first hatch and full bloom (cv. McIntosh) ranged from 5 to 14 days. Wide variation was also observed in the relationship between fruit bud development and first hatch of the overwintered eggs. In peach orchards, overwintered eggs hatched usually within a 2-week period but in some years this took three weeks. Consequently a more accurate method, applicable to peach and apple orchards, was required to forecast hatching of overwintered eggs of the European red mite.

Predicting the beginning of hatch, or 50% hatch, on the basis of accumulated degree-days has been unsuccessful in England (Light et al. 1968). Extended hatching periods, variation from year to year in the date of peak hatch, and variation of peak hatch from one orchard to another are factors that rendered

‘Present address: Agriculture Canada, Research Branch, Research Program Service, K.W. Neatby Bldg., C.E.F., Ottawa, Ontario. K1A 0C6.

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forecasting difficult. Cranham (1972) showed however, that a close forecast of the date of 50% hatch in England depended on two factors, effectiveness of chilling and accumulated degree-days. In Japan, Tsugawa et al. (1961) have been successful in forecasting first hatch of ERM overwintered eggs from temperatures in March and April. However, hatching there was more synchronized than in Ontario; 99% of the hatch in the field occurred within ten days, mainly before the blossom period.

This paper reports on the influence of temperature, humidity, and vapour pressure deficit (V.P.D.) on the development of ERM overwintered eggs and describes methods of degree-day summations to forecast first and 50% hatch, and the subsequent testing of the indices under Ontario conditions.

Materials and Methods

Twigs infested with ERM overwintered eggs were collected in March from a sour cherry orchard near Vineland, Ontario. Twigs of ca. 1.5-cm diameter were cut in the orchard into 10-cm lengths. In an open-sided insectary, twigs were examined under a binocular microscope and a twig section bearing about 100 viable eggs was selected and ringed with polybutene stickem. Twigs were secured to wire mesh platforms with florists’ clay. Twigs and platforms were then placed in clear plastic containers (17 x 12 x 6 cm) and moved to the laboratory. In the laboratory, 100 ml of specific saturated salt solutions were poured into the bottoms of the containers to maintain the constant relative humidity (Winston and Bates 1960) and achieve a desired V.P.D. Containers were closed with clear plastic covers and moved into appropriate constant temperature cabinets with a 16L:8D photoperiod regime. Relative humidities were maintained within = 5% as follows: 10.0°C, 40 and 70%; 12.5°C, 70% R.H.; 15.0°C, 55, 70, and 80% R.H.; 17.5°C, 70% R.H.; 20.0°C, 70 and 85% R.H.

Each of the nine treatments was replicated three times. Hatching was moni- tored by examining the eggs daily in a S°C room with a binocular microscope and emerged larvae caught in the stickem were removed with a needle. Data were subjected to Duncan’s multiple range test. Multiple stepwise regression analyses were also conducted to determine the influence of temperature and humidity on development of ERM overwintered eggs. The temperature threshold of develop- ment was estimated by subjecting data for days to first and 50% hatch relative to constant laboratory conditions of 10 to 20°C, in increments of 2.5°C, and 70% R.H. to two types of mathematical treatments. One treatment consisted of solving the linear function: Y=a-+bx, where Y was the rate of development at tempera- ture X, and a and b were constants; the intercept and slope respectively. The second treatment consisted of solving the hyperbolic function (Trottier 1971): T = a:/(X-Th), where T was the time for first or 50% hatch at temperature xX; Th was the calculated temperature threshold, and a: was the minimal accumulated temperature in degree-days above Th.

The temperature threshold established from laboratory data that offered the least variation in degree days among the temperature treatments was used to calculate degree-days to first and 50% hatch in the field.

Two methods of dd summation were evaluated for estimating ERM egg development in the field. They were:

1) dd = dd: = (T max + T min)/2-Th

(T max + T min)/2-Th for T min=Th

(T max + Th)/2-Th for T min < Th 54

D2) dd = dda

Proceedings of the Entomological Society of Ontario Volume 110, 1979

where T max and T min are respectively the maximum and minimum temperatures for the day, and Th is the temperature threshold established in the laboratory.

Maxithum and minimum temperatures were recorded with an accuracy of + 0.5°C in standard Stevenson Screens located in the orchards. Degree-days (dd) were accumulated daily from March 1 and April 1 to the day of occurrence of first and 50% hatch in the field.

Degree-day relationships to first hatch in the field were tested by using the 1969-73 data from peach orchards in the Jordan-Vineland area (Herne and Trottier 1975). Degree-day relationships to first and 50% hatch were also tested by using biological and weather data from apple orchards in different climatic areas over the years 1971-1978.

Results and Discussion

Laboratory study

At all temperatures the rate of egg development to first hatch was about 1.5 times faster than to 50% hatch (Table 1). The interval between first hatch and

TABLE I. Days for hatching of diapause eggs of P. ulmi and percentage of eggs hatching at different constant temperatures and 70% relative humidity.

Temp Number Mean % No. Days for Hatching XG Eggs Hatch First 50% 100% 10.0 310 43.5a 38 (2.63 )* 56.0 (1.79) * 90 (1.1)* p25) 296 77.4b 28 (3.57) 43.5 (2.30) 83 (1.2) 15.0 298 56.4¢ 20 (5.00) 32.5 (2.08) 58 (1.72) 17.5 297 39.1d 15 (6.67) 23.5 (4.26) 49 (2.09) 20.0 306 56.5 c¢ 10 (10.00) 16.5 (6.06) 34 (2.94)

Means followed by different letter are significantly different from each other at the 0.05 probability level. * Percentage development per day in (_).

50% hatch increases as temperature decreases. Per cent hatch at 12.5°C was larger (P < 0.05) than at the other temperatures, while at 17.5°C per cent hatch was smalier (P < 0.05). Cranham (1972) found that the per cent hatch was greater at 15 than at 21°C. The linear and hyperbolic functions in this study were solved by using the interval to hatch data (Table II). The temperature threshold for development, 5.6 + 0.5°C, gave the least variance between temperature treat- ments; the coefficient of variability (C.V.) ranged from 11.3 to 15.3% for estimating mean dd to first hatch; from the interval to 50% hatch, the temperature threshold of 5.1 + 0.5°C allowed the best estimates (C.V. ranged from 11.5 to

TaBLe II. Temperature threshold (Th) and mean degree-days (dd), for development of over- wintered eggs of P. ulmi incubated at constant temperature and 70% relative humidity, estimated by two methods.

First Hatch 50% Hatch Function iC) ad == (S:D)): Th (°C) dd + (S.D.) Y=a+ bX V2 Betas (Qil72) 6.7 236.0 + (34.0) T = a:/(X-Th) 5.6 174.2 + (19.6) 5. 291.9 + (33.5)

* Standard deviation

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Proceedings of the Entomological Society of Ontario Volume 110, 1979

14.4% ). Table II shows that the temperature threshold 5.6°C, which produced the least variance is the best estimator for ERM overwintered egg development. Therefore dd to first hatch and 50% hatch in the field are predicted to approxi- mate 175 and 275 respectively. Cranham (1972) calculated the threshold of winter eggs of P. ulmi by fitting a linear regression between rate of development and temperature, but warned of the limitation of extrapolation methods. Although he calculated that the threshold was within the range 5.5-7°C, the lowest tempera- ture permitting development and eclosion of a high proportion of winter eggs was 9°C; for a small percentage it was 8°C.

Lees (1953) stated the threshold for post-diapause development of P. ulmi winter eggs was 7°C, although he did not indicate whether eclosion would occur. Parent (1965) used an extrapolation method and found the threshold of summer eggs to be 8.9°C. Mori (1957) also determined by extrapolation that the develop- ment threshold of summer eggs was 9.03°C but stated the real threshold was probably lower because the extrapolated line was merely theoretical and ‘practic- ally’ the line was s-shaped with the ends curved. Putman (1970) working with summer eggs, determined the lowest experimental temperature at which eggs completed embryonic development and hatched was 10.8°C., but considered the threshold to be 1 to 3°C lower.

At 10°C, but not at 15°C, V.P.D. influenced days to first and 50% hatch (Table III); days before hatching increased with low humidity. This may be due to the lower hatch recorded at low humidity (P < 0.05). No significant influence,

TABLE III. Effect of temperature and vapour pressure deficit (V.P.D.) on hatching of over- wintered eggs of P. ulmi under constant laboratory conditions.

Temp. V.P.D. R.H. Number Mean % No. Days for Hatching (2@) (mb) (% ) Eggs Hatch First 50% 100% 10 3.68 70 ano 43.5 a 384... S60laoO 15 3.41 80 298 49.0 a 19b 320b #£63b 10 7.36 40 267 13.7b 46c 66.7c 86a 15 7.67 55 298 25.8b 21b 35.56 }=60b

Means followed by different letter are significantly different from each other at the 0.05 probability level.

however, was found in our study for days to total hatch. Table I shows that optimum hatch occurred at 12.5°C and 70% R.H. or at a V.P.D. of 4.346 mb. Any departure below or above these conditions reduce per cent hatch (Table II).

Table IV shows the combined effect of temperature and V.P.D. on rate of development of ERM overwintered eggs. Temperature alone explains about 94% of the variance between treatments, and V.P.D. 97%. However, 99% of the variance is explained by the multiple regression models,

Y: = —0.0663 — 0.0134 X + 0.0616 X: Y: = —0.0369 — 0.0079 X + 0.0364 X:

where Y: is the rate of development to first hatch, Y, is the rate of development to 50% hatch, X is temperature, and X: is V.P.D. Therefore, temperature and avail- able moisture have a synergistic effect on rate of development. Furthermore, it is clear from Table IV, although relative humidity was constant (70% ), that V.P.D. increased from 3.682 mb at 10°C to 7.012 mb at 20°C. Tables I, III and IV show

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Proceedings of the Entomological Society of Ontario Volume 110, 1979

therefore, that available moisture expressed as V.P.D. has a significant influence on ERM egg development and that relative humidity is a less useful expression of ambient moisture conditions.

Mori (1957) showed with summer eggs of P. ulmi the importance of the amount of water vapour present in a given volume of air on embryonic develop- ment and hatching. For example at 17% R.H. the per cent of embryos developing (but not hatching) was 0 and 48% at temperatures of 15 and 20°C respectively.

TABLE IV. Effect of temperature (X) and vapour pressure deficit (V.P.D.) (X:) on rate of development (Y) of overwintered eggs of P. ulmi incubated at constant temperature and 70% relative humidity.

Rate of development*

Temp. V.P.D. First Hatch 50% Hatch (°C) (X) (mb) (X;) (Y 1) (Y2)

10.0 3.682 0.0263 0.0179 125 4.346 0.0357 0.0230 15.0 5.113 0.0500 0.0308 17/25) 5.997 0.0667 0.0426 20.0 7.012 0.1000 0.0606 Y-Intercept (a) —0.0663 —0.0369 Reg. Coeff. 1 (b:) —0.0134** —(0.0079*** Reg. Coeff. 2 (bz) + 0.0616** 010364525 R-Squared (R*) 0.9959 0.9994

= Rate of development; Y=a+ b.X + bX; ** Significant at the 0.01 probability level. (0.1 < S.L. < 0.05) *** Significant at the 0.05 probability level. (0.05 < S.L. < 0.01)

At 28-33% R.H. the per cent hatch was 0 and 13% at temperatures of 15 and 20°C respectively. A given volume of air with the same relative humidity obviously holds more water vapour at 20 than at 15°C.

Field Study

In Table V the lowest C.V. occurs with dd: summations indicating that this ‘is the more accurate way to calculate dd above 5.6°C to first hatch in peach orchards, and that summations should start from 1 March near Vineland, Ontario. For other fruit growing areas summations of dd: should start when maximum

TABLE V. Comparison of degree-day (dd) summations above 5.6°C (Th) to forecast first hatch of overwintered eggs of P. ulmi in a peach orchard.

Degree-day Summations

Including Excluding Date of March °C March °C First Hatch dd; dd, dd: dd, Mean 7 May iy N5y7/ 105 137 Coefficient of 19 15 8 20 19

Variation (% )

temperatures exceed 5.6°C. The C.V. was 8% for dd: summations starting in March compared to 15, 19 and 20% for the other methods. Therefore ca 155 dad: above 5.6°C after March 1 can be used to predict first hatch in the field. How- ever, this value is 20 dd: lower than the 175 dd established in the laboratory. Such

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Proceedings of the Entomological Society of Ontario Volume 110, 1979

a difference may be related to the influence of V.P.D. on rate of development (Table IV) which was not measured in the field. Based on 155 dd: above 5.6°C the predicted dates of ERM first hatch for apple orchards in different climatic growing areas were found to be accurate within one day (Table VI). Since 1975, predicted dates for first hatch of the ERM overwintered eggs, for all major fruit- growing areas, have been used by the extension horticulturists of Ontario as early warnings for the onset of ERM development.

In the laboratory study, dd summations to 50% hatch were found more variable than to first hatch (Table II). For two consecutive years observations were made in three apple growing areas in an effort to relate 50% hatch to dd apoves)-o © atter March 1. A’ sum of.250 dd: == .20. (S.D.) was found to be related to 50% hatch. This value is ca 25 dd: lower than the 275 dd established in the laboratory. This difference may also be due to the influence of V.P.D. (Table IV). Based on 250 dd:, predicted and observed dates of 50% hatch were found to be within three days (Table VII).

This study shows the value of biometeorological indices determined in the laboratory, in predicting biological events. However, such indices often must be modified after field testing to obtain acceptable accuracy for a specific field situation. The dd: summations above the temperature threshold (5.6°C), permit accurate forecasting of hatching time of the ERM overwintered eggs in widely different climatic areas. Such information is important and useful in the efficient operation of Integrated Pest Management programmes.

Acknowledgments

The authors thank Mr. C. T. Lund of this Station and E. Johnson now with Chipman Inc., for their assistance with experiments. We also thank Ontario Ministry of Agriculture and Food Extension Horticulturists for their assistance in testing the biometeorological indices in the different apple-growing regions of Ontario.

References

CRANHAM, J. E. 1972. Influence of temperature on hatching of winter eggs of fruit-treé red spider mite, Panonychus ulmi (Koch). Ann. appl. Biol. 70: 119-137.

HERNE, D. H. C., and R. TRoTTIER. 1975. Relationships between hatching of eggs of Euro- pean red mite and fruit bud development in Ontario peach and apple orchards. Proc. ent. Soc. Ont. 106: 4-8.

HERNE, D. H. C., and T. Lunp. 1979. Simulation model of European red mite population dynamics developed for a mini-computer. Can. Ent. 111: 449-507.

JOHNSON, E. F., R. TROTTIER, and J. E. LAING. 1979. Degree-day relationships to the develop- ment of Lithocolletis blancardella Fab. and its parasite Apanteles ornigis Weed. Can. Ent. 111: 1177-1184.

LeEEs, A. D. 1953. Environmental factors controlling the evocation and termination of dia- pause in the fruit tree red spider mite Metatetranychus ulmi (Koch) (Acarina: Tetrany- chidae). Ann. appl. Biol. 40: 449-486.

LicHT, W. I. St G., JoHN, M. E., GouLp, H. J. and CoGuiL1, K. J. 1968. Hatching of the winter eggs of the fruit tree red spider mite (Panonychus ulmi (Koch) ). Ann. appl. Biol. 62: 227-239.

Mor!, H. 1957. The influence of temperature and relative humidity upon the development of the eggs of fruit tree red spider mite Metatetranychus ulmi (Koch) (Acarina: Tetrany- chidae). J. Fac. Agric. Hokkaido (imp.) Univ. 50:.363-370.

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PARENT, B. 1965. Influence de la température sur la développement embryonnaire et post- embryonnaire du tétranyque rouge du pommier, Panonchus ulmi (Koch) (Acariens: Tetranychidae) Ann. Soc. ent. Qué 10: 3-10.

PUTMAN, W. L. 1970. Threshold temperatures for the European red mite Panonychus ulmi (Acarina: Tetranychidae). Can. Ent. 102: 421-425.

TROTTIER, R. 1971. Effect of temperature on the life-cycle of Anax junius (Odonata: Aeshnidae) in Canada. Can. Ent. 103: 1671-1683.

TROTTIER, R. Early warning system for apple pest management in Canada. Bull. OEPP (in press).

TsuGAWA, C., YAMADA, M. and SHIRASAKI, S. 1961. Forecasting the outbreak of destructive insects in apple orchards. III. Forecasting the initial date of hatch in respect of the ~ Overwintering eggs of the European red mite. Pananychus ulmi (Koch), in Aomori Prefecture. Jap. J. appl. ent. Zool. 5: 167-171.

WINSTON, P. W., and D. H. BATEs. 1960. Saturated solutions for the contro! of humidity in biological research. Ecology 41: 232-237.

(Received 27 December 1979)

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Proceedings of the Entomological Society of Ontario Volume 110, 1979

INFESTATION OF MACROSIPHUM AVENAE AND RHOPALOSIPHUM PADI (HOMOPTERA: APHIDIDAE) ON WINTER WHEAT IN ESSEX COUNTY, ONTARIO

W. H. Foott, A. H. TEICH and W. M. ELLIOTT Research Station, Agriculture Canada, Harrow, Ontario NOR 1G0

Abstract Proc. ent. Soc. Ont. 110: 61-63 (1979)

A widespread infestation of aphids on winter wheat was of great concern to growers in Essex County in June, 1979. It was found that light to severe infesta- tions on the heads of wheat at the time that kernels were half-filled did not reduce the yield or test weight of the crop. A heavy driving rain was effective in reducing aphid populations on the plants. Small plots sprayed with malathion demonstrated that effective control was available if necessary.

Introduction

Winter wheat growers in Essex County, Ontario were greatly concerned during June, 1979 because of aphid infestations in their fields. The aphids infested all visible parts of the plants, but of particular concern was the large numbers on the heads at a critical period of grain development. The kernels in many of the fields were only half-filled. A quick decision was necessary as to whether an aerial application of aphicide should be recommended.

The growers said that they had never experienced similar infestations, and the literature failed to provide any useable information on previous infestations, damage, or control studies on winter wheat in Ontario. Because of this lack of available information, our findings are published as a guide for future investigators.

Materials and Methods

Fields were examined in several areas of the county to determine the extent of the infestation, the species of aphids involved, and predator and parasite activity. Sample heads were placed in 70% alcohol and the aphids counted and identified later.

On June 19, a 240 m’ area in a field of the Fredrick variety of wheat at Harrow was divided in six equal parts and 150 plants/plot were examined to determine the percentage infestation. Three of these plots were treated with malathion 50 EC at a rate of 1.5 1/ha using a knapsack sprayer. After 24 and 48 hours all plots were examined to assess changes in infestations.

Kernels were removed from infested and uninfested heads on June 20 and examined in the laboratory to observe any injurious effects of the aphids. A 6.75 m’ area in each plot was harvested on July 30 to determine yields and test weights (kg/hl).

Results and Discussion

From our observations and those of about 70 growers who either attended meetings or contacted us, it was apparent that the infestation was widespread. Two

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species of aphids, namely, the English grain aphid, Macrosiphum avenae (Fabri- cius), and Rhopalosiphum padi (L.), sometimes referred to as the oat bird-cherry aphid, were present on most plants examined. The numbers of aphids per plant and the ratio of M. avenae to R. padi varied so greatly between plants and between fields that a determination of averages per field was meaningless. However, in two samples where counts were made in commercial fields there were 87 and 67/head. In general terms, it could be stated that the infestations ranged from light to severe, with most being in the moderate category. Each field that we observed had coccinellid and syrphid predators and some aphids had been parasitized.

The percentages of plants with infested heads in the six experimental plots before treatment on June 19 were similar (Table I). On June 20, there was a large decrease in the numbers of infested plants in the treated plots, but a small increase

TABLE I. Percentages of winter wheat plants infested with aphids before and after treatment with malathion.

Mean % of plants with infested heads

Date Untreated plots" Treated plots* June 19° USA) ae Oise 17.38 226 June 20° Soe =a ES 5.3 2a June 21 Uses les) (C58) aus 22.74

“ Means based on 3 plots, 150 plants examined per plot. » Treatments applied after counts made this date.

© Heavy rain occurred after counts made this date.

“ Standard error.

in the untreated plots. Despite their small size, large numbers of dead aphids were readily observed on the ground in treated plots. The few treated plants that remained infested usually had only 1 to 3 aphids/head.

The experimental plots and much of the county were affected by a storm soon after the records were taken on June 20. Approximately 24 mm of rain fell on the plots within a few hours and there was a moderately strong wind. Examina- tion on June 21 showed that this driving rain resulted in a substantial decrease in the number of aphids per head in untreated plots, although there was only a slight decrease in the percentage of infested plants (Table I). Large decreases were also observed in a commercial field where the average number per head was 78 before the storm and 15 after. Limited data from a commercial field showed that 74% of the adult aphids on the heads were R. padi on June 19 but only 4% were of this species on June 21, so this smaller species appeared to have suffered more from the rain than M. avenae. It was also noted that the rain had a minimal effect on predators and that adult parasites were emerging from the mummified aphids.

An insecticide treatment was not recommended when we met with the growers on the evening of June 21 because there was no evidence from our examination that kerriels had been injured up to that time, the rain had substantially reduced aphid populations on the heads, and predators and parasites of aphids were active in the fields. This recommendation appears to have been correct; the treated and untreated plots had similar yields, 4197 and 4407 kg/ha respectively. These yields were not less than in plots of the previous year when there was no significant aphid infestation. Likewise the mean test weights of 70.9 for untreated and 71.0 kg/hl for treated plots were not statistically different. Nevertheless, we had some concern at the time because the amount of rainfall varied widely throughout the

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county, with some areas receiving only one-half that recorded at the research station. However, there was a record high yield in the county of 4100 kg/ha and there were no test weight problems — a certain symptom of insect or disease damage.

Conclusions

Light to severe aphid infestations on the heads of winter wheat during the first half of grain filling did not reduce yields or test weight. A heavy, driving rain effectively reduced aphid populations and was a major factor in advising growers not to treat their fields. It was demonstrated that an application of malathion at the recommended rate would have provided effective control if a treatment had been necessary. The decision not to recommend an aerial application of insecti- cides saved the growers approximately $25/ha. There were about 28,745 ha of winter wheat in Essex County in 1979.

(Received 18 January 1980)

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Proceedings of the Entomological Society of Ontario Volume 110, 1979

GROUND BEETLES IN THREE TILLAGE PLOTS IN ONTARIO AND OBSERVATIONS ON THEIR IMPORTANCE AS PREDATORS OF THE NORTHERN CORN ROOTWORM, DIABROTICA LONGICORNIS (COLEOPTERA: CHRYSOMELIDAE)

B. M. J. TYLER’ and C. R. ELLIs Department of Environmental Biology, University of Guelph, Guelph, Ontario NIG 2W1

Abstract Proc. ent. Soc. Ont. 110: 65-73 (1979)

Adults of 23 species of ground beetles (Coleoptera: Carabidae) were collected at Elora, Ontario, from corn fields (Zea mays (L.)) prepared with zero, minimum and full tillage. The six most numerous species, in a decreasing order of abun- dance were: Pterostichus melanarius Ill., Clivina fossor L., Agonum muelleri Hbst., Bembidion quadrimaculatu:n oppositum Say, P. lucublandus Say, and Harpalus affinis Schr. The seasonal abundance of these species in the three tillage systems were similar. The species most reduced in the full-tillage system were A. muelleri, P. lucublandus, and H. affinis.

Adults of P. melanarius, C. fossor, A. muelleri, B. q. oppositum, Tachys sp., Trechus apicalis Mts., Harpalus pensylvanicus DeG., and several carabid larvae became radioactive when confined with the natural fauna of soil samples includ- ing larvae of northern corn rootworm that were labelled with *P; and Carabus nemoralis Mull., C. fossor, and P. melanarius became radioactive when confined in similar free choice cages with rootworm eggs labelled with '°I. Probably these beetles preyed on rootworms in the field.

Introduction

Predation and tillage are two factors that influence corn rootworm survival. The ground beetles (Coleoptera: Carabidae) Pterostichus lucublandus Say (Kirk 1971) and Harpalus pensylvanicus DeG. (Kirk 1973) were reported to feed on rootworms; and Musick and Collins (1971) speculated that numbers of rootworm larvae were smaller in a reduced-tillage system than in a conventionally-tilled system because the numbers of predators were greater. Musick and Collins’ hypothesis is plausible because, according to Anderson and Huber (1972), the numbers of the predacious ground beetle, Bembidion quadrimaculatum oppositum Say, were greater in a minimum- than in a full-tillage system. Because the northern corn rootworm is a major pest of corn in Ontario and because knowledge of its natural controls is limited, it is important to investigate if the carabids occurring in Ontario are predators of rootworms and if reduced tillage favours their popula- tions. Reported here is a list of the species of carabids found in corn fields at Elora, Ontario, a comparison of the species and numbers in three tillage regimes and some notes on their importance as predators of rootworm eggs and larvae.

Materials and Methods

Adjacent plots of corn prepared with zero, minimum, or full tillage as described by Tyler and Ellis (1974) were at the Ontario Ministry of Agriculture and Food Research Station at Elora, Ontario. The schedule of operations they described for the tillage systems, the seed treatments, and the herbicide and fertilizer applications were the same each year from 1970 to the spring of 1975

‘Present address: 1041 Brookview Ave., Burlington, Ontario L7T 1V7 65

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with three exceptions. The plot with minimum tillage was not disced as thoroughly in 1974 as in other years because the ground had started to freeze. The corn in the plot with full tillage was harvested as silage in 1974 and not incorporated into the soil; and P.A.G. SXIII was the variety planted in the zero- and minimum- tillage plots while Funk’s G4082 was planted in the full-tillage plot in 1975. Each tillage treatment contained four replicate-areas (56 x 30 m) and both the treat- ments and replicates were separated by 3-m strips that were without corn.

Adult carabids were collected from pitfall traps. These traps were 2.4-m eaves troughs closed at each end with end pieces and placed in the soil level with the soil surface. The traps were covered with plywood strips (0.2 x 2.6 m) that were held about 2 cm above the ground surface to keep out debris and rain but allow arthropods to enter. Water was never found in the traps. One trap was randomly positioned in each replicate-area and all traps reset every two weeks from 9 May until 8 Oct. Carabids that fell into these traps during a 48-hour period were collected by hand or with a portable vacuum, stored in 70% ethanol, and later sorted. The data were transformed with logw (x + 1) for analyses of variance and the means compared with Duncan’s new multiple-range test.

The predator-prey relationships between. carabids and rootworm larvae and eggs were investigated by confining suspected predators with labelled rootworms. The larvae and eggs were previously labelled and were then placed into containers filled with soil and roots from the base of corn plants in the field. Organisms already in the soil were unlabelled and provided the predators with alternatives to radioactive rootworms for food. Although this experimental design reduced the forced feeding problem when predators are confined alone with prey, there was the disadvantage that secondary and primary predators could not be differentiated.

Rootworm larvae were labelled with “P by confining them in petri dishes for 48 hours with the roots of corn seedings that had been immersed for 24 hours in a ’P solution (Na:*PO: in HCI solution) The larvae were then rinsed in distilled water and twenty were placed into each of three containers (2000 cc) filled with the soil and corn roots. Twenty-four hours later, the insect fauna in the containers were supplemented with carabid adults and larvae (Table I) collected from pitfall traps. The containers were sealed and stored in an environmental chamber at 24 + 1°C with a 16-hour photoperiod. After two weeks, the arthropods were recovered by washing the soil through a series of screens with openings of 2 mm, 425 »m, and 177 um. The beetles and larvae were then rinsed with distilled water and preserved in 70% ethanol until their radiation could be determined. Single specimens also collected from pitfall traps but not exposed to “P were the controls. All organisms were removed from the ethanol, dried on filter paper, and placed into vials. An equal amount of a scintillation liquid, composed of toluene (liquid scintillation counting grade) and the fluors PPO (2,4-diphenyloxazole) and POPOP (p-bis- 2-[(5-phenyloxazole)] benzene), was then added to each vial. The contents of each vial were monitored for radiation with a liquid scintillation counter within two half-lives of *P.

Rootworm eggs were labelled with “I by immersing them for one hour in a solution of Na’ in sodium thiosulphate. The eggs were rinsed with distilled water and 100 were placed in two containers filled with soil and roots. Adults and larvae of carabids were collected from pitfall traps and divided into three groups. The first group (Table I) was placed in the two containers 24 hours after the labelled eggs had been added. The containers were then sealed. The last two groups were used for controls. Individuals from one group were placed in separate containers with soil that was sterilized and contained no radioactive eggs. Because there was

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Proceedings of the Entomological Society of Ontario Volume 110, 1979

TABLE I. A list of carabid species exposed in containers to radiolabelled rootworm eggs and larvae for 14 days and the number labelled.

Rootworm Stage Number Number Labelled Carabid Species Recovered Labelled Larvae with *P Adults Agonum muelleri Hbst. 1 1 Bembidion quadrimaculatum oppositum Say 2 1 Carabus nemoralis Mull. 1 0 Clivina fossor L. 5 2 Harpalus pensylvanicus DeG. 2 1 Prerostichus lucublandus Say p, 0 P. melanarius Ill. 9 5) Tachys sp. 4 1 Trechus apicalis Mts. 1 1 Larvae (several spp.) 6 6 Eggs with '°I Adults Agonum muelleri Hbst. 31 0 Bembidion quadrimaculatum oppositum Say p 0 Carabus nemoralis Mull. 14 1 Clivina fossor L. 3 D Harpalus affinis Schr. 1 0 Lasiotrechus discus F. 1 0 Patrobus longicornis Say 1 0 Prterostichus lucublandus Say 18 0 P. melanarius Ml. 16 2 Tachys sp. 6 0 Trechus apicalis Mts. 8 0 Larvae (several spp.) 4 0

a possibility that the “I solution would diffuse from the eggs and contaminate the carabids, single specimens of A. muelleri, C. nemoralis, C. fossor, P. lucublandus, P. melanarius, T. apicalis, and Tachys sp., composing a second control group, were each sealed in a container with soil contaminated with radioactive rinse water. All containers were kept in a growth chamber maintained at 15 + 1°C and with a 12-hour photoperiod. After two weeks, carabids were screened from the soil, rinsed in distilled water, and placed in separate vials. An equal amount of 70% ethanol was added to each vial and the radiation was monitored with an automatic gamma counter within one half-life of “I. Organisms with high counts were rinsed with distilled water and recounted.

Radiation counts in both experiments were adjusted for the decay of the isotopes by using standards and were expressed as counts per minute. The average counts per minute of each arthropod was compared with those of the control groups using Scheffe’s Test (Guenther 1964).

Results and Discussion

Twenty-three species of carabids were collected from the pitfall traps (Table II) and 13 of these species were common to each tillage system; namely Harpalus pleuriticus Kby., Notiophilus aquaticus L. and the 11 species of Table II. Ptero- stichus melanarius Ill. was the most abundant composing 64% of the total number collected from each tillage regime (Tables II and III). This species attained maximum numbers in all tillage plots in July (Fig. 1A). The next most abundant

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Proceedings of the Entomological Society of Ontario Volume 110, 1979

400 @ TILLAGE N ie bascdekenes a Full PN e—-—e Minimum \ Pterostichus melanarius Ill.

@ @ @ @ e @ @

AVERAGE NUMBER PER- TRAP

i . Clivina fossor L. 10 :

oe

° es o .2

. °

of

of

o- WS wo

Pe, ®e ®e, 2e

July . | Sept. COLLECTION DATES

FIGURE 1. The seasonal abundance of adult carabids in corn fields under three tillage systems at Elora, Ont.: A, Pterostichus melanarius; B, Clivina fossor.

species were Clivina fossor L. (Fig. 1B), Harpalus affinis Schr. (Fig. 2A), P. lucublandus Say (Fig. 2B), Agonum muelleri Hbst. (Fig. 2C), and Bembidion quadrimaculatum oppositum Say (Fig. 2D). The seasonal abundance of these species in the three tillage systems were similar and maximum numbers were collected on the same dates in the three tillage systems. Instances when one species was statistically more abundant (P = 0.05) in one tillage system than the others are tabulated in Table IV. In general, C. fossor was more numerous in the tilled

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Proceedings of the Entomological Society of Ontario Volume 110, 1979

NUMBER PER TRAP

AVERAGE

TILLAGE Acceesecen a Full e—-—@ Minimum

Harpalus affinis Schr.

o- WO Ww

July Aug. Sept.

Pterostichus lucublandus Say

=~ wo ao N © ms /

15

10

Oo- wo oa

May July Aug. Sept. Oct.

Bembidion quadrimaculatum oppositum ay

om wan

COLLECTION DATES

FIGURE 2. The seasonal abundance of adult carabids in corn fields under three tillage systems at Elora, Ont.: A, Harpalus affinis; B, Pterostichus lucublandus; C, Agonum muelleri; D, Bembidion quadrimaculatum oppositum.

systems (Fig. 1B) whereas P. melanarius was less numerous in the full-tillage system during maximum abundance in July (Fig. 1A). Full tillage resulted in generally lower numbers of H. affinis (Fig. 2A), P. lucablanbus (Fig. 2B), and A. muelleri (Fig. 2C). The differences between zero and minimum tillage were not consistent and, in fact, the total numbers collected in the minimum was greater than in the full tillage system (Table II).

A number of carabid adults and larvae became labelled (P = 0.05) when

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Proceedings of the Entomological Society of Ontario

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Proceedings of the Entomological Society of Ontario Volume 110, 1979

TABLE IV. Dates when adults of any one species of carabids were more abundant in corn fields managed with either full, minimum or zero tillage.

Date Species Significant Differences (P < 0.05) 23 June Clivina fossor L. more numerous in the full- than in the zero- or in the minimum-tillage plots 7 July Pterostichus more numerous in the zero- and minimum- than in the melanarius Ill. full-tillage plot 25 July C. fossor more numerous in the full- and minimum- than in the zero-tillage plot 28 Aug. Bembidion more numerous in the minimum- than in the full-tillage

quadrimaculatum — plot oppositum Say ii; C. fossor more numerous in the minimum- than in the full-tillage plot

confined with radioactive rootworms (Table I). The apparent predacious nature of most of the carabid species in these experiments concurred with observations in the literature. A. muelleri, B. q. oppositum, C. fossor, H. pensylvanicus, P. melanarius, and Trechus spp. were reported to feed on immature stages of insect pests (Fox and MacLellan 1956; Wishart et al. 1956; Mitchell 1963; Johnson and Cameron 1969; Best and Beegle 1977 a, and b). Because of the experimental design we can conclude that the carabids that became labelled were either preda- tors of rootworms or were involved in a food chain that included rootworms. Some of the ground beetles may have fed on labelled rootworm eggs and larvae but were no longer radioactive at the time of monitoring. P. melanarius became radioactive when confined with both larvae and eggs. Because a relatively high proportion of this species became labelled with “P and because it was the most

abundant carabid in all tillage regimes from July to the end of Sept., P. melanarius was the most influential carabid predator for reducing the numbers of rootworm larvae. C. fossor, the second most abundant carabid, also became radioactive from both eggs and larvae. However, because this species was significantly less abundant in the zero-tillage system, it probably had less impact as a predator of rootworms in this regime than in the minimum- and full-tillage regimes. All six carabid larvae became labelled with “P indicating they were active predators during the labora- tory studies and may be in corn fields. In general, because more individuals and species were radioactive after confinement with the larvae than with the eggs, carabids are probably more important as predators of rootworm larvae in the field.

Acknowledgments

The authors extend their thanks to Mrs. R. J. Hines, Dr. I. R. Tizard, Dr. G. A. Robinson of the University of Guelph. This research was supported by the Ontario Ministry of Agriculture and Food and in part by Grant No. A 6500 to C. R. Ellis from the National Research Council.

References

ANDERSON, M. J. and R. T. Huser. 1972. A comparison of the effects of two corn tillage

systems on adult populations of selected ground beetle species. Proc. N. Centr. Br., ent. SOG. Amer 21. lige

Best, R. L. and C. C. BEEGLE. 1977a. Food preferences of five species of carabids commonly found in Iowa cornfields. Environ. Ent. 6: 9-12.

Best, R. L. and C. C. BEEGLE. 1977b. Consumption of Agrotis ipsilon by several species of carabids found in Iowa. Environ. Ent. 6: 532-534.

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Proceedings of the Entomological Society of Ontario Volume 110, 1979

Fox, C. J. S. and C. R. MACLELLAN. 1956. Some Carabidae and Staphylinidae shown to feed on a Wireworm, Agriotes sputator (L.), by the precipitin test. Can. Ent. 88: 228-231.

GUENTHER, W. C. 1964. Analysis of Variance. Prentice-Hall Inc., Englewood Cliffs, New Jersey. 199 pp.

JOHNSON, N. E. and R. S. CAMERON. 1969. Phytophagous ground beetles. Ann. ent. Soc. Amer.

62: 909-914.

KirK, V. M. 1971. Ground beetles in cropland in South Dakota. Ann. ent. Soc. Amer. 64: 238-241.

Kirk, V. M. 1973. Biology of a ground beetle, Harpalus pensylvanicus. Ann. ent. Soc. Amer. 66: 513-518.

MITCHELL, B. 1963. Ecology of two carabid beetles, Bembidion lampros (Herbst) and Trechus quadristriatus (Schrank). I. Life cycles and feeding behaviour. J. Anim. Ecol. 32: 289-299.

Musick, G. J. and D. L. CoL.ins. 1971. Northern corn rootworm as affected by tillage. Ohio Rep. Res. 56: 88-91.

TYLerR, B. M. J. and C. R. ELtis. 1974. Adult emergence, oviposition and lodging damage of northern corn rootworm (Coleoptera: Chrysomelidae) under three tillage systems. Proc. ent. Soc. Ont. 105: 86-89.

WIsHaRrT, G., J. F. DOANE, and G. E. MAYBEE. 1956. Notes on beetles as predators of eggs of Hylemya brassicae (Bouché) (Diptera: Anthomyiidae). Can. Ent. 88: 634-639.

(Received 25 June 1979)

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Proceedings of the Entomological Society of Ontario Volume 110, 1979

A COMPARISON OF DEVELOPMENT AND FECUNDITY IN NORTH AMERICAN AND EUROPEAN POPULATIONS OF THE CEREAL LEAF BEETLE, OULEMA MELANOPUS (COLEOPTERA: CHRYSOMELIDAE)’

J.C. GUPPY Ottawa Research Station, Agriculture Canada, Ottawa, Canada K1A 0C6

Abstract Proc. ent. Soc. Ont. 110: 75-78 (1979)

North American and European populations of the cereal leaf beetle, Oulema melanopus (L.) were observed side by side under controlled conditions. Beetles from North America were more fecund and after 10 months of storage oviposited over a longer period than European beetles even though total longevity did not differ. Duration of the egg stage at 5S constant temperatures was identical in both populations but larval development differed significantly at 17° and 31°C, suggest- ing adaptation to different temperature ranges in the two populations.

Introduction

In 1975, studies on the life system of the cereal leaf beetle, Oulema melano- pus (L.) were initiated at Ottawa to determine, in part, its economic potential and environmental limits in Ontario. Because the insect was scarce and sporadic through most of its native range (Haynes 1973) its rapid spread in the U.S. mid- west and into Ontario during the 1960’s suggested that a more vigorous strain may have developed in North America. Therefore, it was of interest to determine the factors that affect the fitness of the different populations. This is a report on some aspects of the comparative biology of beetle populations derived from Europe and North America and maintained at Ottawa under identical conditions during a two-year period.

Methods

Adults of O. melanopus were field-collected during the summer following pre-hibernation feeding by D. L. Haynes of Michigan State University at East Lansing, Michigan, and by K. P. Carl of the Commonwealth Institute of Biological Control, at Delémont, Switzerland. After roughly eight months of storage under conditions as described by Connin et al. (1968) the beetles of each population were released by the writer into separate ovipositional cages containing potted Laurier barley and held at 25°C and 60% R.H. with a 16:8h LD photoperiod. The barley seedlings, 10 to 15 cm high, were renewed daily and examined at intervals of 4-6 h during the daytime to obtain freshly laid eggs.

Developmental rates of the egg and larval stages were compared by side by side rearing of samples taken from each ovipositional cage, following the methods of Guppy and Harcourt (1978). Observations were made at 5 temperatures 17°, 22°, 25°, 27°, and 31°C using 50 to 100 eggs and not less than 30 larvae of each population.

For studies on the adult stage, individuals of each population were reared on potted barley under conditions as described above and the resulting adults stored at 5°C. Following 27, 35, and 42 weeks of storage, 10 sexual pairs of beetles,

‘Contribution No. 602 Ottawa Research Station, Agriculture Canada 75

Proceedings of the Entomological Society of Ontario Volume 110, 1979

from each colony each period, were caged individually in plastic cages (17 x 8 x 4 cm) and supplied with barley seedlings held in 25 ml vials. Mating frequency was recorded during two one-hour periods at mid-morning and mid-afternoon each day for 10 days. Eggs were counted every second day. Size of beetles was com- pared by measuring the length of the right elytron of all female beetles in these tests.

Data were compared using t-tests to determine statistical significance.

Results and Discussion Development

The duration of the egg stage was the same for both the North American and the European populations at each of the five experimental temperatures (Table I). However, developmental time for the European larvae was significantly

TABLE I. Mean duration + S.E. (days) of the egg and larval stages of two populations of Oulema melanopus at constant temperatures.

Stage and Temperature (°C)

Population / 2 2S Dal 31

Egg N.A. 113220205 6.0 + 0.07 49+ 0.04 AVoy se O08 3.8 == 0106 EUR. tiles yeu ORO) 620 ==) 0207. ANS) ae()0)8} AV) s=(0)(0)3) Bats ae W.O7/

Larva N.A. 73h a (0) P27) 10.3 + 0.09 83) == OND 712 = ]0106 63)-= On EUR. 1NCG,) aust (01S) LOG == OFS: 8.1 + 0.06 Wsyae (Ysi'8) 6.9 + 0.14

t-value’ 2Z8Oe%5 1.41 [E42 0.39 Sli

"For difference in larval development **Significant at 1% level

shorter at 17°C and longer at 31°C than for the North American larvae. At 17°C the difference in developmental time between the two populations was spread equally among all instars but at 31°C this differential occurred mainly during instars 3 and 4. When the data were compared to rate of development curves as given by Guppy and Harcourt (1978) the rate for the North American larvae declined slightly at 31°C as expected while that for the European larvae declined sharply. A decrease in the rate of development in response to increased tempera- ture is a type of stress reaction to temperatures approaching the upper limit for an insect and it is often more evident in the later instars (Guppy and Mukerji 1974). Since response of both groups of larvae to the three intermediate tempera- tures was similar, the data suggest that the two populations differ in temperature limits only.

Fecundity

Table II shows that the numbers of eggs laid by laboratory reared females of the two populations after each of three storage periods was not significantly different even though the mean number laid by the North American beetles was consistently higher. However, standard errors were high due to using only 10 pairs of beetles per test. When the data from the 3 storage durations were pooled (Table II), the number of eggs laid by the North American beetles was signifi- cantly greater than that laid by the European beetles. Further evidence of this

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disparity was indicated by the distribution in number of beetles classified by egg production categories as follows:

No. eggs laid 0-100 101-200 201-300 301-400 N.A. beetles 12 8 4 6 Eur. beetles 20 7 2 1

This difference in the number of eggs laid was observed in the original beetle populations received from Michigan and Switzerland when it became apparent

TABLE II. Fecundity of two populations of laboratory reared females of Oulema melanopus.

Mean number of eggs per beetle + S.E.

Test Weeks No. Storage N.A. Eur Difference t-value 1 ay) 186.3 + 28.9 124.9 + 31.3 61.4 Lei) 2 35 196.3 + 34.0 112.6 + 26.8 83.7 1.93 3 42 126.0 + 46.4 58.4 + 20.5 67.6 1.20 Average 169922271 102.4 + 19.0 67.5 PES ayert

**Significant at 1% level

that the European beetles laid fewer eggs after being placed into the oviposition cages. However, this may have been due partly to differences in pre-hibernation food quality or some other unknown factor affecting the beetles prior to storage. The results obtained from laboratory reared beetles indicate that true differences exist. There was no difference in elytral size between populations of laboratory reared female beetles from North America or Europe.

Oviposition activity and longevity

Following 27 weeks of storage the pre-ovipositional period for the European beetles was four days longer (Table HI), but after storage periods of 35 and 42 weeks it was the same as that of North American populations. This indicates a

TABLE III. Mean number of days + S.E. post-storage longevity and ovipositional activity of adult females of Oulema melanopus.

Weeks Pre-ovipositional Ovipositional Post-storage storage period period life span N.A. 27 joo) a Oe DONA aie 446+ 5.41 35 4.0 + 0.37 PA Soy aust 8) 0) 41.0 + 4.45 42 == leOS QLD AO 3758) a= nS Eur. Di], 98 == 0596" = 23.1 + 6.06 Dee = ON) 85) 5.3 + 0.67 19.4 + 3.69 SEY) sasha) 42 Vio as O57) MIE OR 284 SOs 14a **t — 4.28, significant at 1% level *t — 2.60, significant at 5% level

difference in requirements for hibernation. After 42 weeks of storage, length of the ovipositional period of European females was half as long as that of North American females. There was no significant difference between populations in overall longevity.

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Mating behaviour

In the original stock, caged in lots of 50 to 70 beetles, the European beetles appeared to be more sedentary and mating appeared to be less frequent among these beetles than those from Michigan. However, in the laboratory reared popula- tions there was no difference in the general activity level and feeding, nor was there a difference in mating frequency. Beetles of both groups generally mated twice per day and averaged about 9 matings in 10 days.

Conclusion

Since the origin of O. melanopus in North America is unknown, we cannot conclude from the data presented here that a biological strain of the insect has — developed therein but only that one population in North America is different from one in Switzerland in terms of fecundity and temperature limits for larval develop- ment. The differences observed may be important adaptations of the life system of the two populations. These differences were readily detected and more profound ones may exist.

References

Guppy, J. C. and D. G. Harcourt. 1978. Effects of temperature on development of the immature stages of the cereal leaf beetle, Oulema melanopus (Coleoptera: Chrysomelidae). Can. Ent. 110: 257-263.

Guppy, J. C. and M. K. MUKERJI. 1974. Effects of temperature on development rate of the immature stages of the alfalfa weevil, Hypera postica (Coleoptera: Curculionidae). Can. Ent. 106: 93-100.

(CONNIN, R. B., D. L. Coss, J. C. ARNSMAN and G. LAWSON. 1968. Mass rearing the cereal leaf beetle in the laboratory. U.S. Dep. Agric. Res. Serv. ARS 33-125. 11 pp.

Haynes, D. L. 1973. Population management of the cereal leaf beetle, Jn P. W. Geier, L. R. Clark, D. J. Anderson, and H. A. Nix (Eds.), Insects: Studies in population management. Mem. ecol. Soc. Aust. 1: 232-240.

(Received 1 February 1980)

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SUSCEPTIBILITY OF CULEX SPP. AND AEDES SPP. LARVAE (DIPTERA: CULICIDAE) TO TEMEPHOS AND CHLORPYRIFOS IN SOUTHERN ONTARIO

B. V. HELSON, G. A. SURGEONER and W. E. RALLEY Department of Environmental Biology, University of Guelph, Guelph, Ontario N1G 2WI1

Abstract Proc. ent. Soc. Ont. 110: 79-83 (1979)

At 19°C, 24-hr LCs’s for fourth-instar Culex pipiens (L.), Culex restuans Theo- bald and Aedes vexans (Meigen) to temephos (Abate®) were 1.03, 1.15 and 3.00 ppb (ug/1), respectively. No evidence of resistance could be detected in Culex spp. larvae from sites treated repeatedly over three years with temephos (LCs = 0.92 ppb). At 14°C, 24-hr LCs’s of fourth-instar Ae. stimulans (Walker), Ae. euedes Howard, Dyar and Knab, Ae. canadensis (Theobald) and Ae. excrucians- fitchii were 5.11, 2.47, 4.42 and 3.33 ppb, respectively. The 24-hr LCw’s of C. pipiens and C. restuans fourth-instar larvae to chlorpyrifos (Dursban®) were 0.46 and 0.41 ppb, respectively, at 19°C.

Introduction

Following the 1975 outbreak of St. Louis Encephalitis, SLE, (Mahdy et al. 1979) many municipalities in southwestern Ontario initiated mosquito larviciding programs. Control efforts were directed primarily against Culex pipiens, the sus- pected vector of SLE in Ontario (Helson et al. 1980). Larval control of other species has also been undertaken because of their annoyance to humans or their potential as vectors of other arboviruses. Although chlorpyrifos (Dursban®) has been used by some municipalities (MacKenzie 1977) temephos (Abate®) has been used most commonly in Ontario.

Resistance of mosquito larvae to organophosphorous insecticides, including resistance to temephos and chlorpyrifos (Gillies et al. 1968b), can develop as a consequence of continuous extensive exposure (Georghiou et al. 1975). Conse- quently, it is important to regularly monitor the susceptibility of larval populations to determine if resistance is developing before control failures occur.

The susceptibility of species of mosquitoes most commonly being controlled in southern Ontario is presented in this paper. The only published data for mos- quito susceptibility in southern Ontario is that by Brown et al. (1954) for DDT. Our data were collected from various regions of the province with no known history of insecticide treatment and are considered to represent unexposed popu- lations. This study should provide baselines for future comparisons to determine if resistance is developing. Tests were also conducted on C. pipiens and C. restuans larvae collected from sites which had been treated at least 10 to 20 times with temephos from 1976 to 1978, to determine if resistance was developing.

Materials and Methods

Mosquito larvae were collected from natural breeding sites in various counties of southern Ontario, predominately Essex, Niagara and Wellington. In areas where Culex spp. larvae were being controlled few larvae could be collected from breed- ing sites. Consequently, oviposition pools (Surgeoner and Helson 1978) were placed immediately adjacent to treated sites. C. pipiens and C. restuans egg rafts and larvae were collected weekly from these pools, transported to the laboratory

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at the University of Guelph and reared to 4th-instar for testing. Because resistance is a genetic phenomenon, populations adjacent to regularly treated sites should exhibit resistance if present.

In the laboratory, larvae were identified and 25, 4th-instars placed into a 200 ml Lab-Tek® plastic specimen ,container containing 199 ml of distilled water. Larvae of Ae. fitchii (Felt and Young) and Ae. excrucians (Walker) were not separated because of the handling and possible injury required to separate these species. A fresh 200 ppm (mg/1) stock solution of technical temephos (95.7% ) or chlorpyrifos (99.0% ) in 99, Mol % acetone was prepared before each test. Appropriate solutions were prepared by serial dilution so that 1 ml of solution when added to 199 ml of water provided the desired insecticide concentration. The 1 ml solutions were dispensed into each cup using a 1 ml Eppendorf® automatic pipette. The contents were stirred and covered with a cardboard lid to reduce evaporation.

Each concentration was tested against two or three groups of 25 larvae each. One ml of acetone was added to the controls. All larvae were then transferred to an incubator and held at 19 + 1°C for the summer species and 14 + 1°C for the spring species. These temperatures were selected as they represent water tempera- tures to which the 4th-instar larvae would be exposed in field situations in southern Ontario.

Mortality was assessed after 24 hr. Dead and moribund larvae were com- bined for mortality determinations. Larvae were considered moribund if unable to flex head to siphon when stimulated with a probe. Only tests with 3 to 5 concen- trations, providing average mortalities between 10 and 90% were included. Tests with control mortalities greater than 20% or with greater than 10% pupation were excluded also. Results were analyzed by an APL probit analysis program based on Finney (1971) to provide 24-hr LC» and LCw values.

Results and Discussion

The LCs and LCw values for temephos (Table I) against C. pipiens larvae were similar to other studies, using a variety of techniques, from different areas of

TABLE I. 24-hr LCs. and LCw (ppb) values for temephos using fourth-instar larvae of selected mosquito species collected in southern Ontario.

No. of Temp. EG=5 95% (G) Ge |LOies 95% CL* Species Year ©) Trials: °C Lower Upper Lower Upper C. pipiens 1977 14 19 0.98 0.88 1.08 ey 1.60 1.84 1978 3 19 1.24 1.08 1.40 2.15 1.78 DD. C. restuans 1977 il 19 V2) 1.05 1.37 gpr7) 1.96 2.58 1978 3 19 1.03 0.79 1 27/ 1.92 1.02 2.82

C. pipiens-restuans 1978 12 19 0.92 0.80 1.04 1.70 1.43 eS 7/ (previously treated

sites )

Ae. vexans S77 8 19 3.00 B95) 2.49 4.85 3.81 5.89 Ae. stimulans 1977 33 14 4.86 3.96 5.76 6.78 S25) 8.31

1978 10 14 5.19 3.50 6.88 8.34 5.62 11.06 Ae. euedes 1978 6 14 2.48 2.03 2.93 4.65 Be5)7/ S03 Ae. canadensis 1977 1 14 4.42 — — 9.59 — — Ae. fitchii-excrucians 1977 1 14 4.26 = — 5.66 — —

1978 2 14 2.88 2.80 2.96 6.38 3.83 8.93

* Confidence limits of mean LC values.

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the world (Anonymous 1970; Jones et al. 1976; Rettich 1976; Rettich 1977; Sinégre 1967; Sutherland 1971; Sutherland and Evans 1976). The mean LCs value in those studies was 0.90 ppb with a range of 0.32-1.6 ppb and the mean LC» was 1.61 ppb with a range of 0.54-2.8 ppb. The susceptibility of C. pipiens in Ontario was within this range. By contrast, values of ca. 100 ppb have been recorded for resistant populations of C. pipiens (Georghiou et al. 1975).

The ratio of the LC» to LC» value is indicative of the state of susceptibility in mosquito populations (Gillies et al. 1968a; Pelsue et al. 1972). Susceptible populations generally have an LC» approaching but not exceeding twice the LCs value. As the proportion of tolerant individuals increases in a population, the LCw/LC» ratio increases to greater than two. Eventually, when resistance is well established the LCw/LC» ratio again approaches two, due to elimination of sus- ceptible individuals from the population. For field populations of C. pipiens in Ontario, the mean LC»#»/LC» ratios in 1977 and 1978 were 1.81 and 1.73, respectively, indicating a susceptible population. No larvae tested from various regions of the province demonstrated consistent ratios greater than two.

The likelihood of resistance in C. pipiens and C. restuans populations was evaluated further by collecting larvae from regions of Niagara and Essex Counties where larviciding had taken place as required in 1976, 1977 and 1978. LC» and LC» values for these larvae were not significantly different from populations without prior insecticide exposure. The LCw/LC» ratio of 1.84 was also indicative of a susceptible population.

The susceptibility of C. restuans populations to temephos was similar to that of C. pipiens. Values obtained for C. restuans (Table I) were slightly higher than those in two other studies where the LC» value ranged from 0.30-0.49 ppb and the LC» from 0.46-1.1 ppb (Jones et al. 1976; Sutherland and Evans 1976).

TABLE IT. 24-hr LCs) and LC values (ppb) for chlorpyrifos using fourth-instar Culex restuans and Culex pipiens larvae collected in southern Ontario.

No. of Temp. 1G; 95% (G) Gi Wes 95% CL Species Weal enialsiia © Lower Upper Lower Upper C. restuans 1978 Bee To Oli on) Osa Moos 092) 1.04 C. pipiens 1978 2 19 0.46 0.26 0.66 0.88 0.72 1.04

* Confidence limits of mean LC values.

As shown here (Table II) and in earlier studies (Sutherland and Evans (1976), Sinégre (1967) and Rettich (1977)) chlorpyrifos is more toxic than temephos to C. pipiens and C. restuans. Our results were similar to other studies which reported LC» values ranging from 0.13 (Steelman ef al. 1967) to 3.0 ppb (Mulla et al. 1966).

Ae. vexans was less susceptible to temephos than C. pipiens or C. restuans which agrees with Rettich (1977) and Sutherland and Evans (1976). The LCs value of 3.00 ppb was slightly higher than that obtained by Rettich (1977) but may be explained by the fact that our studies were conducted at slightly lower temperatures (19°C vs ca. 22°C). The LC»/LC» ratio of 1.6 indicates that the Ae. vexans population was susceptible.

Spring Aedes spp. larvae were also less susceptible to temephos than Culex spp. LCs values were higher than reported for Ae. stimulans in New Jersey (ca. 5

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ppb as compared to ca. 1 ppb (Sutherland 1971)) and Ae. canadensis in New Jersey and Pennsylvania (4.4 ppb as compared to <1.5 ppb (Sutherland and Evans 1976; Jones et al. 1976) ). We believe that the susceptibility values for Ae. euedes and Ae. fitchii-excrucians are the first to be reported in the literature. Again, the LCw/LC» ratios were less than two for those spring Aedes spp. tested more than twice.

The LCs and LCw values reported here generally agree with those of other studies. They are slightly higher for spring Aedes spp. and Ae. vexans but these differences are considered insignificant as Rettich (1976) has shown 2-3 fold difference in susceptibility of C. pipiens and Ae. cantans 4th-instar larvae of different sizes. Differences may also be explained by inherent variations in natural populations, differences in experimental and holding conditions. Marked differ- | ences in susceptibility of Aedes sp. larvae at different temperatures to temephos have been observed by the authors and will be reported elsewhere. Evidently, resistance of mosquito larvae to organophosphorous insecticides does not exist at present in southern Ontario. Results reported here should serve as baselines for future comparisons, if resistance is suspected.

Acknowledgments

The authors wish to thank Mr. Scott MacDonald, Mr. Carl Nielsen and Mr. Blair McAteer for technical assistance. This research was funded by the Ontario Ministry of Environment through the Ontario Pesticide Advisory Committee.

References

ANONYMOUS. 1970. Abate insecticide in public health programs. Comprehensive Research and Development Manual. Cyanamid International, Wayne, New Jersey. 66 pp.

Brown, A. W. A., J. A. ARMSTRONG and D. G. PETERSON. 1954. Investigation of suspected resistance of mosquitoes to DDT in southern Ontario. Mosq. News 14: 192-194.

FINNEY, D. J. 1971. Probit Analysis. 3rd ed. Cambridge Univ. Press, New York. 333 pp.

GEORGHIOU, G. P., V. ARIARATNAM, M. E. PATERNAK and C. S. LIN. 1975. Evidence of organophosphorous multiresistance in Culex pipiens quinquefasciatus and Culex pipiens pipiens in California. Proc. Calf. Mosq. Control Assoc. 43: 41-44.

GILLIES, P. A., D. J. WOMELDORF and K. E. WHITE. 1968a. Interpretation of resistance in California Aedes nigromaculis larvae. Proc. Calif. Mosq. Control Assoc. 36: 78-81.

GILLIEs, P. A., D. J. WOMELDORF and K. E. WHITE. 1968b. Cross-tolerance of California Aedes nigromacunlis (Ludlow) larvae to EPN, Abate and Dursban. Proc. Calif. Mosq. Control Assoc. 36: 85.

HELSON, B. V., G. A. SURGEONER and R. E. WRIGHT. 1980. The seasonal distribution and species composition of mosquitoes (Diptera: Culicidae) collected during a St. Louis Encephalitis surveillance program from 1976-1979 in southwestern Ontario. Can. Ent. (in press).

JonEs, G. E., D. F. CARROLL and W. WILLS. 1976. Susceptibility of Pennsylvania mosquito larvae to Abate®, Dursban® and Baytex®. Proc. N.J. Mosq. Control Assoc. 63: 161-164.

MACKENZIE, D. L. 1977. Mosquito Control. Municipal Abatement Programs: 1976. Ont. Min. Environ. Publ. 184 pp.

Manupy, M. S., J. M. JosHua and L. SPENCE (Editors). 1979. Arboviral encephalitides in Ontario with special reference to St. Louis Encephalitis. Ont. Min. Hlth. Publ. 364 pp.

MULLA, M. S., R. L. METCALF and G. Kats. 1966. Laboratory and field evaluations of new mosquito larvicides. Mosq. News 26: 236-242.

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PELSUE, F. W., G. C. MCFARLAND and P. A. GILLIES. 1972. Public health protection chemical resistance in larval Culex pipiens quinquefasciatus Say and Culex peus (Dyar) in the southeast mosquito abatement district. Proc. Calif. Mosq. Control Assoc. 40: 25-29.

RETTICH, F. 1976. Changes in susceptibility to temephos, pirimiphosmethyl, fenitrothion and bromophos during preimaginal development of mosquitoes. Acta ent. bohemoslov 73: 382-387.

RETTICH, F. 1977. The susceptibility of mosquito larvae to eighteen insecticides in Czecho- slovakia. Mosq. News 37: 252-257.

SINEGRE, G. 1967. Toxicité de 4 insecticides sur quelques especes de Culicides et sur la faune des gites larvaires. Interdépartmentale pour la demoustication du littoral méditerraneen. Docu. #8. pp. 78.

STEELMAN, C. D., J. M. GassteE and B. R. CRAVEN. 1967. Laboratory and field studies of mosquito control in waste disposal lagoons in Louisiana. Mosg. News 27: 57-59.

SURGEONER, G. A. and B. V. HELSON. 1978. An oviposition trap for arbovirus surveillance in Culex sp. mosquitoes (Diptera: Culicidae). Can. Ent. 110: 1049-1052.

SUTHERLAND, D. J. 1971. Susceptibility of New Jersey mosquito larvae to DDT, Abate and Baytex. Mosq. News 27: 482-487.

SUTHERLAND, D. J. and E. S. Evans, Jr. 1976. Insecticide resistance in New Jersey mosquitoes. A five-year summary. Proc. N.J. Mosq. Control Assoc. 63: 176-181.

(Received 1 February 1980)

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Proceedings of the Entomological Society of Ontario Volume 110, 1979

POPULATION CHANGES OF THE NORTHERN CORN ROOTWORM (COLEOPTERA: CHRYSOMELIDAE) AND CORN YIELD LOSSES IN SOUTHWESTERN ONTARIO

B. C. SMITH

Agriculture Canada, Research Station, Harrow, Ontario NOR 1G0

Abstract Proc. ent. Soc. Ont. 110: 85-91 (1979)

Methods are described for estimating population density of eggs and larvae of the northern corn rootworm, Diabrotica longicornis (Say), and for assessing effects of larvae on yield of corn by comparing plots treated with soil insecticides with non-treated plots. Mean density of larvae in non-treated plots with areas ranging from 16-66 m° was 6.3/plant and mean loss in yield was 0.7 tonnes/ha from 1975-78. Soil treatments of 10% granular carbofuran and phorate applied at a rate of 1.0 kg ai/ha reduced rootworm populations by a mean of 2.9 larvae/plant and increased yield by 14.2%. Addition of superphosphate partly compensated for losses caused by rootworms. The insecticides had comparable efficacies. Dry soil conditions in 1978 were responsible for reductions in density of larvae and in efficacy of insecticides. Yield stimulation by carbofuran occurred at some sites in 1976. A regression equation based on density of larvae and weight of ears in 1977 indicated a loss in yield of 2.5%/larva. Measurements of larval density were less variable in 66 m° plots than in smaller ones, and samples in 22 m? plots of 8% of the area were less variable than those of 4%.

Introduction

The northern corn rootworm, Diabrotica longicornis (Say), is recognized as a pest of corn in southern Ontario (Ont. Ministry Agric. and Food 1974) but there is insufficient information on its economic importance and control. Bereza (1975) reported that the rootworm was becoming more abundant. Tyler and Ellis (1975) described the effects of different tillage systems on egg density and on emergence of adults, and indicated the need for further research on damage caused in full tillage fields. Establishment of the northern corn rootworm in Quebec (Guibord 1976) and the western corn rootworm, Diabrotica virgifera Le Conte, in Ontario (Foott and Timmins 1977) may lead to greater damage under Canadian conditions. In the United States, loss in yield has been related to density of root- worm populations, extent of lodging, and root damage rating (Chiang 1973). Apple et al. (1977) compared plots that were treated with granular carbofuran with non-treated checks in studies conducted in seven states from 1971-74 and reported significant overall losses in three states ranging from 7.5-25.5% of yield. These losses were associated with mean populations of 11.6-22.8 larvae/plant. Pimentel et al. (1978) found that mean densities ranging from 0.4 to 1.0 larvae/ plant caused reductions in yield of 7-22% in New York State. Petty et al. (1969) estimated losses of 0.8% in high density and 1.4% /larva in low density popula- tions. The object of this study was to describe larval populations of the northern corn rootworm and their effects on the yield of corn.

Materials and Methods

Field experiments to determine the effects of northern corn rootworm larvae on yield of corn were conducted in cooperation with growers. Plots were estab- lished on clay and clay-loam soils at various sites in southwestern Ontario from 1975 to 1978. The names and locations of sites were: Campbell and Dawson in

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Proceedings of the Entomological Society of Ontario Volume 110, 1979

Kent, Harper and Selves in Perth, Oil City and Sharp in Lambton, and Stumpf in Middlesex county. Sites selected had been cropped to corn for at least two previous years (continuous corn), had lodging damage, and had a mean density of at least 2.0 rootworm eggs per kg of soil in the spring.

Soil samples for determining density of eggs were collected using a spade with a 15 x 20 cm blade or, when specified, a 6.3 cm i.d. x 15.0 cm high core sampler. The soil sample at a site consisted of one spadeful of soil taken from each of 25 locations to a depth of about 15 cm. The 25 subsamples were taken at intervals of 4 m with alternate left and right turns to the direction of travel. The subsamples from a site were mixed in the laboratory and eggs were extracted from soil units of one litre from soil that was held for two days at 20°C and about 65% RH. At least six units were examined for eggs and density was expressed as numbers per kg of soil. Eggs were separated from soil by sieves (Lawson and Weekman 1966) and magnesium sulfate flotation (Chandler et al. 1966; Matteson 1966). Eggs were counted using a binocular microscope. When the core sampler was used, two or three cores were collected between plants in the rows in June and numbers of eggs per kg of soil were recorded.

Plant roots and the associated soil for determining number of larvae were usually collected during the first two weeks of July. A block of soil about 23 cm in diameter and 15 cm deep was removed with each root system. Roots were washed and the soil was sifted through screens to remove larvae. Three to eight roots were sampled per plot with one or two being selected per row. Larvae of the northern and western rootworm were not distinguished in the larval counts. How- ever, from observations on adult populations the western rootworm comprised about 1, 6, and 20% in 1976, 1977, and 1978 respectively.

Granular insecticides, carbofuran and phorate, were applied to the soil at planting through cone seeders attached to a 3-row International 185 planter. Granules were dropped in a 15 cm band over the seed furrow and covered with soil by dragging a heavy V-shaped chain behind the press wheel. The numbers of larvae and the yield in the treated plots were compared with those of non-treated checks.

Plots were of 4 sizes: about 16 m’ (3 rows x 6 m); 22 m’ (4 rows x 6 m); 44 m* (4 rows x 12 m) and 66 m’ (6 rows x 12 m). Row spacing was 91 cm and plant density was reduced to about 25 plants/6 m of row when plants were 15 cm high. The treatments were replicated 3 to 6 times in randomized blocks.

Plots were planted in May and the practices of cooperating growers were followed in the application of fertilizers and herbicides. In 1975, these materials were experimental variables at Oil City where the level of soil phosphorous was low. They were applied by hand during planting at the following application rates: superphosphate, 67.0 kg/ha; lime, 100.0 kg/ha; and Sutan and atrazine at 4.0 and 1.0 kg/ha respectively.

Yields were determined by hand-harvesting the ears in October and were based on the weight of grain at 15.5% moisture of all plants or of plants in 1 or 2 rows per plot.

In 1977, relationships between the density of rootworm larvae at plots where 8 plants were sampled and various plant measurements were investigated at all sites. Height of ear from ground and per cent of plants with under-sized ears were measured on all plants in a plot about a week before harvest. In the laboratory, ear weight and per cent of plants with ears < 100 g dry weight were measured on corn harvested at 15.5% moisture from 2 rows/plot.

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Data were analysed using analysis of variance, Duncan’s Multiple Range Test, “t” test, and correlation and linear regression. When necessary, data were trans- formed using arc sin. Differences reported are for those that are significant at the 5% level unless otherwise stated. Means are expressed with standard errors.

Results and Discussion

The density of rootworm larvae at plots not treated with soil insecticides varied from 0.8 to 16.5 larvae/plant and yield varied from 2.0 to 9.1 tonnes/ha from 1975 to 1978. In 1975 at Oil City, all plots except those that were treated with carbofuran had high densities of rootworm larvae (Table I). Addition of

TasBLeE I. Effects of carbofuran, superphosphate, lime, and herbicides on populations of northern corn rootworm larvae, height of ear from ground, weight of fresh ear, and yield of corn (Pioneer 3909) at Oil City, Ontario in 1975."

Rate of Weight

application of Larvae/ Height of of fresh Yield Treatment kg/ha plant” ear cm‘ ear, g° tonnes/ha Carbofuran 1.0 0a" 88.1 a" 263.6 a® Spomas Superphosphate 67.0 16.5 b 73.7 ab 204.1 b 2.8 ab Lime 100.0 13.55 79.0 ab 212.6 ab 22D Sutan, atrazine 4 and 1 15.85 72.5 ab 198.4 b 2.1 b Non-treated check 11.85 ND alab 170.1 b 2.0 b

“Mean number of eggs was 82.6/kg of soil. Planting and harvest dates were 25 May and 15 October respectively.

» Means of 5 plants in each of 6 replicates of 44 m? plots on 16 July.

“N =-30

* Means in column followed by the same letter are not significantly different at the 5% level by Duncan’s Multiple Range Test.

superphosphate compensated for the yield reduction of 1.2 tonnes/ha caused by rootworms at a density of 11.8 larvae/plant in check plots. This response to fertilizer was observed only at Oil City, and was probably attributable to the low level of phosphorus at this site in 1975.

In the 17 fields sampled at various sites from 1976-78, the density of root- worm larvae was significantly lower in treated than in non-treated plots in ten comparisons where carbofuran was used and in 11 where phorate was used. Yield was consistently higher in treated than in non-treated plots. Differences in yield were significant in four comparisons where carbofuran was used and in three where phorate was used. Pooling of the yearly data of the various sites usually resulted in a significant difference in yield.

Analysis of the combined data of the Harper, Oegema, Sharp and Stumpf sites in 1976 indicated that the densities of rootworm larvae in both 16 m’ and 66 m* plots were significantly (P < 0.01) higher in non-treated check than in treated plots (Table II). Measurements of larval density were less variable in plots of 66 m* than in those of 16 m’ (Table III). Plots that were treated with carbofuran and phorate did not differ significantly in larval density. However, the yield of plots that were treated with carbofuran significantly exceeded that of non-treated checks whereas those treated with phorate were similar to checks (Table II). Yield stimulation by carbofuran has been described by Apple (1971) and Daynard et al. (1975). Carbofuran and phorate reduced larval density by 64.0-75.0% in 1976 and the overall loss at non-treated plots was 0.7 tonnes/ha which amounted to 10.7-12.7% of the potential yield.

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TABLE II. Mean population of rootworm larvae and yield of corn for plots treated with soil insecticides and for non-treated check plots for all sites in 1976.*

Area of plot Rate of application Larvae/ Yield m° Treatment kg ai/ha plant” tonnes/ha”" 16 Carbofuran 10G 15) Dea dala 16 Phorate 10 G iT) 21a 6.0 b 16 Check SPDib 5.8 b 66 Carbofuran 10 G 1.0 2.la 90D 66 Phorate 10 G 1.0 ESV Se 66 Check 5.0 b 4.8c

“Sites and hybrids were: Harper, Sharp, and Stumpf with P.A.G. SXIII and Oegema with Pioneer 3909. Mean number of eggs were 3.0-10.4/kg of soil. Planting and harvest dates were 26-27 May, 7-26 October respectively.

"Means were based on N = 8 for treated and N = 16 for non-treated 16 m? plots and N = 12 for 66 m* plots. Means in column followed by the same letter are not significantly different at the 5% level. Means within péot classes were compared using Duncan’s Multiple Range Test and between classes using “t” test.

°“N = 4 plants/16 m’ plot and N = 6 plants/66 m’ plot.

*N = 1 row/plot.

TABLE III. Density of rootworm larvae and the yield of corn for plots and samples of different sizes treated with soil insecticides and non-treated check plots in 1976 and 1977.

Larvae/plant, Yield, tonnes/ Treatment mean and SE ha, mean and SE 1976° Carbofuran 10 G 1055) ea) eI 9 fa lee | )-7/ Phorate 10G Dalston (eS 6.0 + 0.4 Check 9D e4 Sree U4! 1976” Carbofuran 10 G Dey a9 6.6 + 0.9 Phorate 10G DQ Sela S21 SS05 Check 50:22 0:6 48 =203 1977° Carbofuran 10 G 6 ==103 10.4+ 0.9 Phorate 10G Icy sus( 0) 74 10.8 + 0.9 Check 4.57207 10:2 209 1977: Carbofuran 10 G ley (02 9.9+ 0.8 Phorate 10 G 2312-1033 10.22307 Check 5.0 + 0.6 8.7 + 0.8

*In 16 m° plots and means based on N = 8-16 with larval samples of 5% of plot area and yield samples of 33% of the crop.

*In 66 m* plots and means based on N = 12 with larval samples of 2% of plot area and yield samples of 33% of the crop.

‘In 22 m* plots and means based on N = 16 with larval samples of 4% of plot area and yield samples of 50% of the crop.

1In 22 m?® plots and means based on N = 16 with larval samples of 8% of plot area and

yield based on 50% of the crop.

Measurements of larval density in 22 m’ plots using a sample that included 8% of the area were less variable than those using 4% (Table III). Analysis of the combined data of the Campbell, Dawson, Selves, and Sharp sites in 1977 indicated that the population density of corn rootworm larvae was significantly (P < 0.01) higher in non-treated check than in treated plots (Table IV). Plots treated with carbofuran and phorate were not significantly different from each other in larval density or yield but they significantly exceeded non-treated check

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plots in yield (Table IV). Carbofuran and phorate reduced larval density by 60.6% in 1977 and the overall loss at non-treated plots was 1.0 tonnes/ha which amounted to 9.9% of the potential yield. Populations were not significantly differ- ent in 1978. Analysis of the combined data of the Campbell, Dawson, and Oil City sites in 1978 indicated that the density of larvae and yield were unaffected by the use of soil insecticides (Table IV). The low levels of rootworm populations and

TABLE IV. Density of rootworm larvae and yield of corn for plots" treated with soil insecticides and for non-treated check plots for all sites in 1977 and in 1978.

Rate of application Larvae/ Yield, tonnes Treatment kg ai/ha plant” /ha” 1977° Carbofuran 10 G 1.0 ea 99a Phorate 10 G 1.0 2.0 a 10.3 a Check 4.7 b 9.1h 1978° Carbofuran 10 G 1.0 inva 4.6a Phorate 10 G 1.0 Ilva 44a Check 0.8 a 4.34 * Plots were 22 m’. > Means were based on N = 32 for 1977 and N = 12 for 1978; means in column followed by the same letter are not significantly different at the 5% level by Duncan’s Multiple

Range Test.

°N = 4-8 plants/plot in 48 plots in 1977 and N = 4 plants/plot in 1978.

*N = 2 rows/plot.

“Sites and hybrids were: Campbell with Pioneer 3780A, Dawson and Sharp with Pioneer 3784; and Selves with Pioneer 3978. Mean numbers of eggs were 2.5-7.0/kg of soil. Planting and harvest dates were 11-20 May and 5-25 October respectively.

* Sites and hybrids were: Campbell with P.A.G. SX 121; Dawson with United 134; and Oil City with P.A.G. SX 12. Mean numbers of eggs were 2.0-3.9/kg of soil. Planting and harvest dates were 11-23 May and 1-17 October respectively.

low yield in 1978 were probably caused by unusually dry soil conditions. Mihm et al. (1974) showed that contact moisture was necessary for egg hatching of the western corn rootworm and this probably also applies to the northern.

Substitution of the 1977 data for density of rootworm larvae in non-treated check and treated plots in the relationship between larval density vs ear weight (Table V) indicated a 7.4% reduction in potential yield in non-treated plots. More work is needed to separate the effects or interactions of corn rootworms and other adverse factors on ear weight, size, and height.

The results of investigations conducted from 1975 to 1978 on northern corn rootworm based on comparisons of plots treated with soil insecticides and non- treated checks showed that populations with a mean density of 6.3 larvae/plant were responsible for a mean loss of 0.7 tonnes/ha that amounted to 14.2% of the potential yield. Carbofuran and phorate treatments did not differ significantly in efficacy or in their capacity to increase yield of treated plots over checks. There were on average 2.9 fewer larvae/plant in treated plots and the yield was 0.7 tonnes/ha greater (Table VI).

Density of larvae and yield of corn varied widely depending on year and site. Mean density of larvae ranged from 0.8-11.8/plant and losses from O-1.2 tonnes/ ha. Depending upon local conditions, the mortality caused by carbofuran and phorate ranged from 0-100% and the mean was 59.9%. The density of rootworm larvae in southwestern Ontario was lower and the losses caused were about the

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TABLE V. Relationships between plot variables including number of corn rootworm larvae per plant and various measurements on grain corn* at the Campbell, Dawson, Selves, and Sharp sites in 1977.

Correlation Variables” Slope Intercept coefficient* Larvae vs ear weight, —5.50 223.37 —0.23* g Larvae vs ear —1.16 93529 —0.18 height, cm Larvae vs under- 2.27 4.4] 0.39** sized ears, % Ear height, cm vs NOD) TNANG 0.82% ear weight, g Unlersized ears, % —2.37 233.50 —0.79** vs ear weight, g Ear height, cm vs —0.63 67.98 —0.69** undersized ears, % Per cent plants with ears —2.37 233.50 —0.80** = 100 g vs ear weight, g Per cent plants with ears —0.77 98.38 —0.70**

= 100 g vs ear height, cm

* Corn varieties were Pioneer 3780A, Pioneer 3784, and Pioneer 3978. » Number of pairs = 48. ° * — significant at 5% and ** = significant at 1%.

Same as reported for Nebraska, Wisconsin, and Missouri from 1971-74 by Apple et al.