Cross generational effects of insecticides on fitness traits of Bracon hebetor Say. And Chrysoperla zastrowi sillemi (Esben-Peterson)

Abstract

The study on‘Cross generational effects of insecticides on fitness traits of Bracon hebetor Say. and Chrysoperla zastrowi sillemi (Esben-Peterson)’wasconductedin the Department of Entomology, Collegeof Agriculture, Vellayaniduring the period 2022-2024. Themain objectives ofthe studywereto assessthedosemortality responses of thelarval parasitoid, B. hebetor and thepredator, C.zastrowi sillemi to new generation insecticidesandto studytheeffect of sublethal doses ofinsecticidesand mild insecticide exposure to fitness traits of these natural enemies. The study on ‘ry film depositionmethodforfixing sub lethal and lethal doses of insecticides againstB.hebetorrevealed that thesublethal (LC5),lowlethal(LC15andLC30)and median lethal (LC50)dosesof the chlorantraniliprole18.50 SCwere1.35 ppm, 4.61 ppm, 12.93 ppm and 47.15 ppmrespectively,at 8 HAT. Thecorrespondingvalues of fenvalerate20ECwere0.78ppm, 2.90ppm, 9.20ppm and he sublethal (LC5), low lethal (LC15 and LC30) and median lethal (LC50) The 2024. The main objectives of the study were to assess the dose mortality responses of the larval parasitoid, B. hebetor and the predator, C. zastrowi sillemi to new generation insecticides and to study the effect of sublethal doses of insecticides and mild insecticide exposure to fitness traits of these natural enemies . ,at 24 HAT. Thecorrespondingvalues offenvalerate 20 EC were0.60 ppm, 2.60 ppm, 8.70 ppm and 29.70 ppm respectively,at 24 HAT. Thecorrespondingvalues offlubendiamide39.35 SCwere2.00 ppm, 7.30ppm, 17.00 ppm and 45.70 ppm respectively,at 24 HATand those of lambda-cyhalothrin 5 EC were0.05 ppm, 0.46 ppm, 2.84 ppm and 18.14 ppm respectively,at24 HAT. Toxicity assay carried out using dry film deposition method for fixing sub lethal and lethal doses of insecticides against 2.00 ppm1.35 ppm). LC5 of LC5 (2.30 ppmn F5,at sublethal doses(LC5)offlubendiamide39.35 SC(2.00 ppm), . The of LC5 in F5. LC5(84.5 per cent) at a LC5 of 1.35 ppmastrowisillemirecordedhighest fecundity(291.6 ± 3.65 eggs), R0(145.0 ± 29.79), finite rateof increase, 𝜆(1.183 ± 9.75) andintrinsic rateof increase, r(0.168 ± 8.26)and GRR(147.7 ±29.54)compared to othertreatments. Egg hatching washighest in chlorantraniliprole18.5 SC(87.1per cent)at LC5(1.35 ppm). . Longevity of females (10.8 ± 0.54 days) was highest in LC5 ( 0.70 ppmforB. hebetorhighest toxicitywas recorded in fenvalerate 20ECand lowest in flubendiamide39.35 SC. Thesublethal concentrations of flubendiamide ) of lambda cyhalothrin 5 EC. Maximum oviposition period was recorded at LC5 (2.30 ppmresulted in increased fecundity, oviposition period and GRR, while fenvalerate showed reduction in the fecundity, R0 and GRR, over the generations.For ) of flubendiamide 39.35 SC (7.7 ± 0.14 days) followed by LC5 of lambda cyhalothrin 5 EC (7.6 ± 0.19 days). Net reproductive rate (R0) was highest in chlorantraniliprole 18.5 SC (29.9 ± 3.47) at LC5. , the highest toxicity was recorded in lambdacyhalothrin5 ECandlowest in flubendiamide39.35 SC. Thesublethal effects (LC5) showedthat, in F5flubendiamide39.35 SCresulted in increasedfecundity, R0and GRR, whereaschlorantraniliprole18.5 SCshowed decreased fecundity, 𝜆, r, R0and GRR.