J. ENTmIOL. Soc. BHI T COI.C~ I H I A 79 (1982). DI' c . 3 1. 1982 25

EFFECT OF A COMMERCIAL INSECTICIDAL SOAP ON GREENHOUSE (HOM: ALEYROD.) AND ITS PARASITOID, ENCARSIA FORMOSA (HYM: EULOPH.) C. S. PURITCH ' Environmcnt Canada. Pacific Forest Research Centre .506 W. Burnside Road. Vi ctoria, B.C. VIIZ 1\1.5

N . T01\KS' Agriculture Canada, Saanich ton Research Station . 8801 East Saanich Road, Sidney. B.C.

P . DOWi\EY3 B.C. Ministry of Agriculture clo 506 W. Burnside Road, Victoria , B.C. V8Z IM5 ABSTRACT Safer's Insecticidal Soap (IS) was topically applied at six concentrations to all growth stages of greenhouse whitefl y as wcll as larvae and adults of the \\'hitefh' parasitoid, the eulophid wasp Encarsia fo rlll osa. IS at 0.5 % ai causcd more than 94 % mortalit" of all whitefly larval stages and adults, and more than 112 ..5 '7.. mor· talit~ · of whitefl, pupae. Adults hatched from treatcd pupae occasionalh' sho\\'ed altered development. E. for lllosa adults were more tol erant to IS than \\·hitcfl,· a nd 81. 5 % survi" ed a 0.5 % IS treatment . It \\'as concluded that IS is an effecti ve pesticide for greenhouse whitefly and should be integrated with E. forlllosa in greenhouse trials.

INTRODUCTION the use of thc parasitoid, E. formosa. has en· The g reenhouse \\·hite fh·. Triale /trodes countered problems. If this small \\'asp is introduc­ vaporarioruln. \Vest\\·ood. ( Homopt e r a: ed at the wrong stage of whitefly development , it Al eyrodidae) is a serious pes t of greenhouse plants. will di e out and additional introductions will be infesting a wide variet" of ornamentals and most necessa ry. Since thc wasp's rate of development is vegetabies, especiallv' cucumbers and tomatoes temperature dependent, being optimum at 21 to (Harris 1974). Besides causing direct damage to 27 °C , temperatures below this level prevent it from plants as a result of feeding on the leaf sap, their breeding as fast as whitefl,·. Whitefl" can therefore honeydew stimulates the growth of soot,· mold cause su bstantial plant damage before the fun gi \\'hi ch disfi gure lea" es and interfere with parasitoid can catch up. E. fo rmosa is Yen' sensitive photo s ~ · nthesi s . to most pesticides and treatments to control the Chemical control of whitefl,' has se,-eral d isad· whitefl" or other pests can easily el iminate vantages. Whitefly eggs arc highl,' res istant to the parasitoicl . almost all insecticides (Harris 1974) and Iar val and Ob,'iously, the best approach to controlling pupal stages are much less se nsitivc than adults \Vhit e fl~ ' would bc onc in which thc parasitoid was (French el al.1973). This variation in the tolerance integrated \\'ith a suitable pesticide that has the of different growth stages coupled with the par· ability to reduce the \\'hitefly population w ithout thenogenic reproduction of whitefly necessitates the harming the wasp. R ece ntl~ ' a fatt" acid salt for· use of repeated spra,'s dllring the growing sea.,o n. mulation has been registered' for the control of Whitefly has been shown to rapid Iv de,'e!op whitefl ,·. This product has also been reported to be r es istancc to most organochlorine and fairl y innocuous to man" hym enopte rous organophosphorous compounds such as BHC and parasitoids. (S . F. Condrashoff, unpublished malathion (Harris 1974). Chemical treatment ma,' data') . It 'HtS decided thcrefore to test this product also encounter a produce problem ",ith ph,·totoxici. for its effect on both T. vapo rariol'1ll11 and E. for­ ty, environmental hazards, and cost. mosa to establish its potential for inclusion in an in· . Enca rsia formosa Cah a n ( H yme nop : tegrated control program for whitefl,·. Eulophidae) has been used successfully in biological control programs against w hit e fl ~ · . Unfortunatcl", MATERIALS AND METHODS Treatments consisted of a water control and 6 concentrations of Safcr's Insecticidal Soap (IS), a CUfn'llt Addrt'...... : 'Safer Agro-Cht:'1ll Ltd . (jiGI J.\irkpalrick Crl':-oct:'l1t. H.B. 1'.'3. \ ' jc­ toria. B,C. VBX .3XI 'Safer'.s In.'.t:'cti cidal Soap (IS). !Hetired. 2810 Graham 51 .. Victuria. B.C. 2S. F. CondrashofL .527 1 Old \\' Saanich Hel ., n .H.•. 3. Victoria, lB.\.. \(inislry of Forests. 1-1 .50 CUH:' Trllllen t SI . Victoria, B.C . fl .C. VBX 3X I. 26 j . E:-:TmlOl., Soc. BrUT, C ()I. U~ 1 1l 1 " 79 (1982), DIOc. 3 1, 1982 commercial 50.5 % fatt,· aeid salt formulation were dead. Pupae were assessed 6 davs after treat­ (Puritch et 01. 1980). Treatments were applied to ment. Fungal growth on the leaf surface made later 0.01, 0.05, 0. 10 , 0 ..50, 1.0 and 1.5 % vlv concentra­ assessments unreliable. Ahnormalities of hatched tions. Tests were carried ou t on every growth stage 1st instars or adults were noted. of whitefly, vis. eggs: 1st , and 2nd and 3rd instars; Adult whitefli es were collected for testing using pupae, and adults. were obtained from a small vacuum-suction device. The vial containing Agriculture Canada greenhouses, where they were the collected whiteflies was chilled bv placing it on being reared a., part of a biological control ice for I min. This treatment immobilized the program. adults and they were separated into individual petri [n the egg bioassa~ ', cucumber lea,'es infes ted di shes , each dish containing 20-30 adults, Each dish with large numhers of freshh' laid whitefly eggs. was chilled again. and the immobilized adults were were selected and taken to the laborator,·. Each leaf sprayed to wetness using the chromatographic was cut into sections. with each seetior{ co ntaining mister. The adults were counted and the dishes at least 50 eggs. The sections were randoml\' assign­ were left uncovered within cages at 22 °C for 24 ed to one of the se,'en treatments. Three replicate Ius., when the\' were assessed · for mortality. A se­ samples ,," ere used per treatment. An a rea within cond group of whitefly adults was treated in the the leaf section was ou tlined with tanglefoot and same manner as just described but the petri d ishes cl eared of all debris, dead eggs and other instar were cO"ered imm e d i at e l~ ' aft er sprayi ng and kept stages. Normal looking eggs were then counted. The co vered for 24 hrs. before assessment. samples were su bsequentl y sprayed to wctness with A bioassay of the toxicity of IS to E, forlllosa their designated treatment usin g a chromatographic that were parasiti zing whitefl ,' scales was made. us­ mister and put on wetted cotton pads in open petri ing the same procedures described for whitefly lar­ dishes. These dishes were placed on laboratory ben­ vac and pupae. Thc assess ments were madc 10 and ches under fluorescent li ghts, at 22 °C for incuba­ 15 da,'s after treatment. Adult E. formosa were tion. After 3 or 4 days all the hatched eggs were treated in a simil ar manner to the adult whitefl y counted and removed. Another assessmcnt was bioassay where the petri dishes were left unco\'ered lIIade 10 days after treatment, which is the normal within cages after spraying. incubation period for whitefly eggs . If normal eggs All tests were corrected for control mortalit,· lIS­ were still evident after the 10-day assessment, obser­ ing Abbott's formula: vations continued until they hatched or desiccated. p -P P = _o__ c X 100 Bioassay of the 1st, 2nd, 3rd instars and pupae t foll owed the basic procedure outlined for the 100 - Pc whitefly eggs. No tanglefoot was used on leaf sec­ tions containing 2nd, 3rd instars or pupae because where Pt = correctly mortality; Pc = control mor­ these stages are immobile. Assessments were made 4 tality (average control mortality as used in the days after treatment of the 1st. 2nd and 3rd instar calculations) and Po = observed mortality. Results stages. The samples were also observed 8 days after for each growth stage were statisticall y analyzed 11.'­ ing a complete randomized block tes t design with 3 treatment to ascertain that the undeveloped larvae

TABLE 1. Percent mortality of various growth stages of grecnhouse wh it en" aftcr topical appli cation of Safer's Insecticidal Soap (IS) (water treated control mortal it\' averaged 10.86 %). \Vithin columns. means not followed by the same letter are signifi cantk different at the 5 '1\ le,·el.

% Hortali ty Con e Developmental Stage of IS Egg 1s t lnstar 2nd lnstar Jrd l nstar Pupae Adults l Ad ults2 a b

0 . 00 (water) O. Oa O. Oa O. Oa O. Oa 0 . 0 O. Oa O. Oa 0 . 0 1 6 . 8ab 3.6a 20 . 5b 4 . 6ab 54 . 2b 8 . 0a O. Sa 0 . 05 3. l ab 34 . 0 b 31. Ob 23 . I b 44 . 1 b 0. 8a l. 2a 0 . 10 5. 9ab 78 . 0c 64 .6c 5 1. 2c 77 .4bc 34 . 7b 25. 2b 0 . 50 6. 8ab 98 . 9d 95 . 2d 94. 8d 82. 5bc 100 . Oc llJO . Dc 1. 00 9.7b 100. Od 98 . &! 95. 8d 9 1.3bc 100. Oc 96 . 6c 1. 50 8 . 4ab 10 0. Od 97. 7d 99 . 7d 95 . 2c 100 . Dc 100 . Oc

Le50 by Probit AnaL 0. 12 0. 04 0.1 0 0. 0 1 0. 16

Treated adults l e ft cove r ed for 24 hours after treatment until assessment

Treated adults l e ft un covered af t e r s praying until assessment at 24 hours

3 Probit not calcul able from data obtained J. E 'JT ()\lOL. Soc. BHIT C O L U ~I B I /\ 79 ( 1982) . DEc. 3 1,1982 27

replicates. and treatment means were compa rcd Some adults that emerged from treated pupae with Neuman-Keul s multiple rangc test. The LC,o suffered from morphological abnormalities. T hese for each growth stage " 'as calcul ated Ilsi ng a probit took the form of improperlv de\'el oped wings or an analysis. absence of the normal wax\' secretions on the body and wings . Puritch (1978)' reported that T c nchrio RESU LTS AND DISCUSSION 1II0/i/or pupae treated w ith potassium salts of oleic All larval instar stages and the adult whitefli cs and li noleic acid , frequent'" devel oped into abnor­ were sentitive to IS application: concentrations of mal adults. It was suggested that the soaps mas' af­ 0. 5 % or greater ga,'e more than 9-1 '7c mortalih' fect the permeability of cell membranes in the (T able I). The m o rtalit~ · of ad ults held in enel osed pupae during the crucial stages of metamorphosis petri dishes for 24 hours after spraying (Adults a. and thereb\' affect the concentrati on and localiza­ Table I) was not differcnt fr om the mortalih' of tion of the 'insect's growth hormones . adults held in open dishcs (Adllits b. T a bl e 1) . Thus Adul t E. formosa were substantia ll \' 111 ore whitefli es th at sur"i" cd the initial topical treat­ tolerant to direct IS than w hi tefl y and sufferccl onls' ment did not succum b to contact with the " 'etted 22.4 % mortali ty at 1.0 % IS. (T a bl e 2) This mo r­ fil ter paper and saturated envi ronment m'er the tality was caused by direct applicati on of IS to the following 24 hours. This suggests that the IS acted imnmobilised E. formosa. Since adult whitefli es ap­ as a contact insecticide and had little res id ual activi­ peared to be unaffected by IS residue, it is likely tv over the testing peri od . that untreated E. form osa landing on treatcd leaves . It wou ld be of interest to determine if the mor­ would also be unaffected by res idues. IIarbaugh tality caused b,' topical treatment would be sim il ar a nd Mattson (1976) applied 5 chemi cals incl uding to the mortalit\· in an otherwise untreated w hi tefl y malathion and ni cotine sulfate to adult E. fo rm osa population exp'osed to treated fil ter paper in a cl os­ at recommended rates and fo und that all com­ ed petri dish . Condrashoff (unpublished rcsearch pounds caused 100 % mortality to the parasitoid . results) noted th at adult whitefli es returning to a Residues of malathion were tox ic to the was ps for wet IS-treated leaf were killed upon landing. It is 2-3 weeks. The larval stages of E. formosa were unclear, howcver. if th ese ad ults had been co n­ more sensitive to IS than were adults ancl had an tacted b\' the spra\' prior to returning to the Icaf. LC,o of 0.15 % IS . No att empt was made in this Pupae rcsponded in the sa me way as the larval study to test different stages of the parasitoid lan·ae. stages bu t were more sensitive at the lower concen­ Perhaps the earlier stages mas' be Icss sensitive. I n­ tration levels " 'ith an a\'erage of 54 % mortality at vestigations on pupae of Argresthja clIpresse/a 0.01 % concentration (Table I). Onls' the eggs " 'ere (cypress leaf miner) treated with IS and paras itized tolerant to the IS treatment with a maximum 1110r­ by the wasp Cha rrno n gracilis showed that 1.0 % IS talill' of 9.7 % at the 1. 0 % b 'c1 of IS . Whitefl y eggs treatment of pupae d id not affect the parasitoid are tol erant to a wide \'ariety of pesticidcs (French (Puritch, unpublished data). e/ at. 1973 ).

TABLE 2. Percent mortali t\· of Enrarsia forlll osa in adult and lan'al (\\'ithin ,,·hitefls · scales) stages. after topical application of Safer's I nsecticiclal Soap (IS). vVithi n column, means not foll owed bv th e same lettcr a re significantls' different at tilt' .'5 0/( level .

% Concentration Developmental Stage of SI Adults Larvae 0. 00 O. Oa O. Oa

0 . 01 O. Oa 14.2a

0. 05 l. 4a 20 . 0a

0.1 s . Oa 27.0a

0.5 18 . sb 78.Sb

l. 0 22. 4b 94. 2b

1. 5 98.2c 97.9b

LC 1.00 0.15 sO 28 J. E"T()~ l ol. . Soc. Bill '!' COI.U~ ·IIllt\ 79 (19R2), DEc:. 3 1, 1982

The high mortalitv caused by concentrations of that incl udes the parasit oid. Encarsia JOT/nusa. IS of 0.5 % and hi gher (Table 1) show that this com­ pound is an effective pes ticide for all whitefl y stages ACKNOWLEDGEMENTS other than eggs. If used at 0.5 % concentration , IS The authors thank Mr. J. Arrand and the B.C. would effectively control whitefly populations \\'ith Ministry of Agri culturc for providi ng the technical little effect on adult E. junnosa. In d ew of the assistance and encouragement for this work. \Ve mam' benefi cial features of the environmentalh' also thank Mr. Don Elliott for donation of the compatible Insecticidal Soap so lution this con';­ whitefli es and parasit oids, and Safer Agro-Chem pound should be assessed in am' integrated program Ltd. for supplying the Insccticidal Soap.

LITERA TURE C ITED Abbott, W . S. 1925. A method of computing thc effectiveness of an insecticide. J. Econ. Ent. 18: 265-267. French, N., F. A. B. Ludlam. a nd L. G. Wardlow . 1973. Observations on the effccts of insecti cides on glasshouse whitefl y [Trialcurodes va porariorulll (Westw. )] P!. Path. 22 : 99- 107. Harbaugh, B. K .. and R. H. Mattson, ]!)76. Insecti cide effects in Encarsia formosa Gahan, parasite of the greenhouse whitefl y. Trialcurodes vaporarinrulll (\Vestwood). J. Am er. Soc. Hort. Sci. 101 : 228-233. Harris, K. M. 1974. Notes frolll W isley: glasshouse whitefh-. J. Royai llort. Soc. 89: 15R - 162. Puritch, G. S. 1978. The biocidal effects of fattv acids on va rious forest pests. Symposium on the phar­ macological effects of li pids. AOCS Monograph No.5: 105- 11 2. Puritch, G. S. , P. C. Nigam. a nd J . H. Carrow. 1980 . Chemical co nt rol of balsarn \\ 'o o ll ~ ' (Homoptera: Adelgidae) on seedlings of Abies amabilis. J . Entomo!. Soc. Brit. Columbia. 77: 15- IR.

THE LETTUCE APHID, NASO N OVIA R1BISN IGRI (HOMOPTERA: ) DAMAGING LETTUCE CROPS IN BRITISH COLUMIHA

A. R. F O RB ES A:\D J. R. MACKEi\ZIF. Research Stati on, Agri culture Canada 6660 i\.W. Marine D ri\'e, Vancouver. B.C. V6T IX2

ABSTRACT The lettuce aphid, Nasoll {Jlj ia rihislligri (Mosle\'), is recorded for the first time as a serious pest of lettuce in the C loverd ale area of British Columbia. In the summer of 198 1 severallcttucc growers in d istinct prcapi cal annul ar circumcision (Fig. 2C) . the Cloverdale area of British Colum bia su ffered Its cauda is finger shaped usuall y w ith 7 hairs (Fig. severe and uncxpectcd crop losses eaused 1)\· the let­ 20), Both Hille m s Lambcrs (1949) a nd Heie (1979) tuce aphid, Naso ll ovia ribislligri (Mosle\) . Although give detailed morphological descri ptions of thc this aphid had been present on other plants in the various morphs of the aphid . \Ve have also collected lower mainland of Fl.C. for mal1\' years (Forhes . and reared a pi nk form of N. ribislligri. in Fl .C. Frazer and MacCarthy, 1(73), it had not been This is an heteroecious aphi d \\'ith Hih es spp. as recorded pre\'iously as a pest of lettuce. The aphid primarv hosts and secondan' hosts in the Com­ was found in marketed heads in September I H8 1 positae and several other plant families. In Fl .C. we and res ulted in an estimated reta il loss of $80.000. coll ectcd adult fundatriccs and fund atrigeniae Crops which were headed up and in fes ted with (most l ~ ' alatc) on black currant, Hih es lIigmm L. , in had to be ploughcd in he·cause the hcads mid-May. Mi gration to lettuce and other seco ndar\' were considered unmarketable. In 1982 lettuce hosts takes place in late Ma \' and in June. Mi gration aphids were found in commercial lettuce plantings back to Hi bes probablv takes placc in September in late May and by the end nf June the\' were caus­ and October. In England during m ild winters some ing rej ection of somc shi pments for marketing, The of the aphids a re abl e to continue to breed on lettuce infestation becamc progressively worse and during outdoors throughout the w inter. This can probabh' August sevcral plantings had to he pl oughed in. occur in the Frasc r Vall e\' too and \\'ould result in Both crisp heading and butter-hcad let tuce crops sizeable populations of lettuce aphids being present were seriously affccted . on O\'erw in ll'red lettuce and other secondan ' hosts N. ribislligri (Fig. 1) is a med ium-sized (2-3 mm r ea d~ ' to infes t newly planted crops in the spring. long) olive-green aphid with a distinctive dorsal In Canada. this aphid has been previoLi sk sclerotic pattern , Its antennae are long w ith secon­ recorded in B.C. , Quebec and 1\'ew Brunsw ick dary sensoria on the basal 114 - 3/4 of scgment III in (S mith and Parron, 1978) . [n the eastern United apterae (Fig. 2A) and all along segment III in alatae States it has been coll ected in 1\' e\\' York, Vermont, (Fi g. 2B). Its cornicl cs are cylindrical. with a Pennsy lvani a, New Jersey. District of Columbia