SCIENTIFIC NOTE. Egg Laying and Development of Different Strains of Trichogramma pretiosum Riley (Hymenoptera: Trichogrammatidae) in Artificial Eggs

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1 Mrço, 1999 An. Soc. Entomol. Brsil 28(1) 173 SCIENTIFIC NOTE Egg Lying nd Development of Different Strins of Trichogrmm pretiosum Riley (Hymenopter: Trichogrmmtide) in Artificil Eggs FERNANDO L. CÔNSOLI AND JOSÉ R. P. PARRA Escol Superior de Agricultur Luiz de Queiroz, ESALQ/USP, Deprtmento de Entomologi, Cix postl 9, , Pircic, SP, Brsil. An. Soc. Entomol. Brsil 28(1): (1999) Oviposição e Desenvolvimento de Diferentes Linhgens de Trichogrmm pretiosum Riley (Hymenopter: Trichogrmmtide) em Ovos Artificiis RESUMO O ojetivo deste trlho foi vlir cpcidde de diferentes linhgens de Trichogrmm pretiosum Riley em prsitr e se desenvolver em ovos rtificiis. Ovos rtificiis form produzidos utilizndo-se um sistem térmico pr deformção de películs de polietileno de lt densidde, otendose 64 depressões semi-esférics (ovos rtificiis) por películ plástic. Os ovos form preenchidos com diet rtificil compost por holotecidos pupis de Ditre scchrlis (Fr.), gem de ovo, soro fetl ovino, hidrolisdo de lctolumin e ntiióticos. Cd ovo rtificil foi oferecido seis fêmes recém-emergids de T. pretiosum, durnte 24 h. A ceitção dos ovos rtificiis (medid pelo número de ovos do prsitóide/ovo rtificil) foi stnte distint entre s diferentes linhgens oservds. A sorevivênci dos estágios imturos em meio rtificil tmém foi vriável entre s linhgens. As implicções dos resultdos pr o desenvolvimento de técnics de crição in vitro pr diferentes espécies e/ou linhgens são discutids. PALAVRAS-CHAVE: Insect, controle iológico, técnics de crição, ceitção do hospedeiro, exigêncis nutricionis, crição in vitro. The in vitro rering of prsitoids hs een developed for mny prsitoid species, ut successful results hve een otined minly for the egg prsitoids in the genus Trichogrmm. Reserch on in vitro rering of these nturl enemies hs een conducted since the 70 s, nd mny countries hve een trying to mss-produce them y using this new technology. However, the success of in mss producing nd relesing in vitro-rered Trichogrmm hs een chieved only y the Chinese (Cônsoli & Prr 1997; Grenier 1997). The development of n rtificil diet is lwys done y using one popultion of species, nd this diet is expect to e suitle for rering other species or strins. However, species from single genus my hve differences in their nutritionl requirements, even for tht polyphgous species exploring the sme kind

2 174 Cônsoli & Prr of resource, such s the egg prsitoids Trichogrmm (Cônsoli & Prr 1996, 1997 ). Yet, strins tht were used to develop on rtificil diets my ecome unle to e in vitro rered, whilst other strins cn still do (Pintureu & Grenier 1992). The selection of strins of Trichogrmm is one of the mjor steps to successfully chieve the iocontrol of specific host species (Hssn 1994). However, strins my hve differences in their fitness to control insect pests ssocited with different groecosystems. In such cses, it would e necessry to produce mny species or strins of Trichogrmm, in order to use the most dequte species/strin in ech pest: groecosystem ssocition. In this work we imed to evlute the ility of different strins of Trichogrmm pretiosum Riley in prsitize nd develop on rtificil host eggs y using stndrd diet. Strins of T. pretiosum were rered on UVtreted eggs of the fctitious host, Angst kuehniell (Zeller), under controlled conditions (temperture: o C; % RH; photophse: 14 h). The fctitious host ws red on lternting diets composed of yest (3%) + whet flour (97%) or corn (40%) + whet flour (60%) (Prr 1997). T. pretiosum strins employed in our study where continuously rered nd mintined on our strin collection, eing identified s strin L1 (host: Helicoverp ze (Boddie); crop: tomto; origin: Alegre - ES, Brzil; sex rtio: 1), strin L2 (host: H. ze; crop: sweet corn; origin: Jguriún - SP, Brzil; sex rtio: 1), strin L4 (host: H. ze; crop: tomto; origin: Jerônimo Monteiro - ES, Brzil; sex rtio: 0.95) nd strin L8 (host: H. ze; crop: sweet corn; locl: Pircic - SP, Brzil; sex rtio: 0.66). Both strins L1 nd L2 were thelytokous. To produce the rtificil eggs, high-density polyethylene memrne (7-8 mm thick) ws lid over the centrl surfce of hot iron plte tht hd sphericl holes. Below this centrl re, chmer ws connected to vcuum pump. After the iron plte ws heted, the vcuum pump ws turned on nd the negtive pressure formed inside the chmer locted under the centrl re pulled the plstic memrne into the sphericl holes. After few seconds the vcuum pump ws turned off nd 64 semi-spheres were formed in the plstic memrne. These memrnes were filled with n rtificil diet previously reported for the in vitro rering of T. pretiosum nd Trichogrmm glloi Zucchi, mde with pupl holotissues of Ditre scchrlis (Fr.) (65%), egg yolk (18%), ovine fetl serum (8.5%), lctlumin hydrolyste (8.5%) nd preservtives (mphotericin B + streptomycin sulphte - 3%). Pupl holotissues were collected from two to five dys-old D. scchrlis pupe produced on n rtificil diet sed on whet germ nd yest (Mcedo et l. 1983). Pupe were het-treted (60-62 o C - 10min) to inctivte the phenoloxidses. Afterwrd, they were surfce sterilized with 0.2% hypochloride solution (2 min), trnsferred for lminr flow chmer nd squeezed into disposle syringe. The holotissues were collected in sterile vil, centrifuged nd the solid phse ws discrded. All steps for diet mnipultion were conducted in lminr flow chmer (Cônsoli & Prr 1997). The rtificil eggs, filled with the rtificil diet, were offered to newly-emerged T. pretiosum femles in proportion of six femles:rtificil egg, during 24 h. We used five replictes nd ech rtificil egg memrne (with 64 rtificil eggs) ws considered s repliction. The ility of the strins of T. pretiosum to prsitize nd develop in n rtificil host egg ws ssessed y evluting the cceptnce of the rtificil host egg nd the prsitoid immture survivl. Egg cceptnce ws mesured y counting the numer of T. pretiosum eggs lid/rtificil egg. After the 24 h oviposition period, femles were removed nd 16 rtificil eggs/rtificil egg crd were smpled nd the numer of T. pretiosum eggs lid ws ssessed using compound microscope. Immture survivl ws mesured y counting the numer of mture lrve tht reched the pupl stge nd the numer of dults eclosed/rtificil egg. All the experi-

3 Mrço, 1999 An. Soc. Entomol. Brsil 28(1) 175 mentl procedure ws conducted under controlled conditions (temperture: o C; % RH; photophse: 14 h). Egg lying in rtificil host eggs y T. pretiosum strins ws very distinct, with strin L4 lying the highest numer of eggs/rtificil egg nd strin L1 the lowest numer (Figure 1). The lower rte of prsitism y strin L1 could e explined y the low egg cceptsurvivorship mong strins when prsitizing the sme host is relted to the genetic vriility mong popultions, s previously descried for T. rssice nd T. voegelei (Chssin & Boulétreu 1991; Mimouni 1991). Also, the success of the preimginl development seems to e host dependent nd it is vrile mong strins of single species (Gomes & Prr 1998). 50 EGG LAYING (numer of eggs/rtificil egg) L1 L2 L4 L8 STRAIN Figure 1. Egg lying (numer of eggs/rtificil egg) of different strins of T. pretiosum in rtificil host eggs (temperture: o C; % RH; photophse: 14 h). Mens (+SEM) followed y the sme letter re significntly different (F = 13.59; df = 3, 19; P < 0.05, Tukey test). nce (rtificil egg with t lest one prsitoid egg) shown y this strin (90%) when compred to the other strins (100%). These strins lso differed on the survivorship of their immture stges when developing on n rtificil diet. Strin L2 showed the higher survivorship, despite the low prsitiztion of rtificil eggs. Strin L1 hd the lowest lrvl survivl, ut the higher pupl survivl (Figur 2). The success in exploiting host during the immture stges of Trichogrmm is geneticlly determined nd the differences in Whether this genetic vriility mong prsitoid popultions of single species implies in distinct nutritionl requirements should e etter investigted. However, this fctor must e considered for the development of n rtificil diet for the in vitro production of prsitoids, when this system is to e used in the control of mny pests on different groecosystems. In such cse, would e necessry to develop one rtificil diet for ech prsitoid species or strins, since the selection of effective strins to control the trget pest in specific crop system is one of the

4 176 Cônsoli & Prr SURVIVORSHIP (%) c 0 L1 L2 L4 L8 STRAIN Lrvl Pupl Figure 2. Survivorship (%) of the immture stges of different strins of T. pretiosum when developing on rtificil eggs (temperture: o C; % RH; photophse: 14 h). Mens (+SEM) within n immture stge followed y different letters re significntly different (lrvl stge: F = 3.59; df = 3, 19; P < 0.05; pupl stge: F = 8.97; df = 3, 19; P < 0.05, Student Newmn-Keuls Method). most importnt fctor involved in the success of using Trichogrmm (Hssn 1994, 1997). Acknowledgement We thnk FAPESP for providing finncil support for this reserch nd the scholrship for F.L. Cônsoli. Literture Cited Chssin, C. & M. Boulétreu Genetic vriility in quntittive trits of host exploittion in Trichogrmm (Hymenopter: Trichogrmmtide). Genetic 83: Cônsoli, F.L. & J.R.P. Prr Comprison of hemolymph nd holotissues of different species of insects s diet components for in vitro rering of Trichogrmm glloi Zucchi nd T. pretiosum Riley. Biologicl Control 6: Cônsoli, F.L. & J.R.P. Prr Produção in vitro de prsitóides: crição de Trichogrmm glloi e T. pretiosum no Brsil, pp In Prr, J.R.P. & R.A. Zucchi (eds), Trichogrmm e o Controle Biológico Aplicdo. Pircic: FEALQ/USP. Cônsoli, F.L. & J.R.P. Prr Development of n oligidic diet for in vitro rering of Trichogrmm glloi Zucchi nd Trichogrmm pretiosum Riley. Biologicl Control 8: Gomes, S.M. & J.R.P. Prr The

5 Mrço, 1999 An. Soc. Entomol. Brsil 28(1) 177 prsitiztion s tool for fctitious host selection for Trichogrmm glloi Zucchi nd T. pretiosum Riley. Mitteilungen us der Biologischen Bundesnstlt für Lndund Forstwirtschft, Heft 356, p Grenier, S.A Desenvolvimento e produção in vitro de Trichogrmm, pp In Prr, J.R.P. & R.A. Zucchi (eds), Trichogrmm e o Controle Biológico Aplicdo. Pircic: FEALQ/ USP. Hssn, S.A Strtegies to select Trichogrmm species for use in iologicl control, pp In Wjnerg, E. & S.A. Hssn (eds), Biologicl Control with Egg Prsitoids. Wllingford: CAB Interntionl. Hssn, S.A Seleção de espécies de Trichogrmm pr o uso em progrms de controle iológico, pp In Prr, J.R.P. & R.A. Zucchi (eds), Trichogrmm e o Controle Biológico Aplicdo. Pircic: FEALQ/USP. Mcedo, N., P.S.M. Botelho, N. Degspri, L.C. Almeid, J.R. Arújo & E.A. Mgrini Controle iológico d roc d cn-de-çúcr. Pircic: IAA/PLANALSUCAR. 22p. Mimouni, F Genetic vritions in host infesttion efficiency in two Trichogrmm species from Morocco. Redi 74: Prr, J.R.P Técnics de crição de Angst kuehniell, hospedeiro lterntivo pr produção de Trichogrmm, pp In Prr, J.R.P. & R.A. Zucchi (eds), Trichogrmm e o Controle Biológico Aplicdo. Pircic: FEALQ/USP. Pintureu, B & S. Grenier Vriility in morphologicl nd iologicl chrcteristics in two strins of the prsitoid Lixophg ditree (Dipter: Tchinide). Biologicl Control 2: Received 26/III/98. Accepted 20/I/99.