摘要：AbstractBackground and objectivesTrichogramma chilonisis an important biological control agent (parasitoid) that kill the host species before they damage the crops. However, insecticide sprayed afterT. chilonisrelease significantly alter its efficacy. The acute toxicity risks of neem seed extract and commonly used insecticides for the control of lepidopteran insects are unknown forT. chilonis. The main objective of this study was to assess the toxicity of four insecticides, i.e., buprofezin, lufenuron, methoxyfenozide, pyriproxyfin and neem seed extract toT. chilonis.MethodsEgg card and dipped surface bioassays were used to test the toxicity insecticides, i.e., lufenuron (2 ml/liter), methoxyfenozide (2 ml/liter), buprofezin (5 g/liter), pyriproxyfin (5 ml/liter) and neem seed extract (2 ml/liter).Egg cardboards prepared from the parasitized eggs ofSitotroga cerealellacollected at 1st, 3rd, 5th, 7th, and 8th day after oviposition were dipped in the respective concentrations of inleticides and neem seed extract. The dipped cardboards were dried and emergence ofT. chiloniswas recorded.Similarly, dipped surface bioassay was conducted to observe the mortality ofT. chilonisat 4 and 24-h after exposure.ResultsThe applied insecticides exhibited varying degree of toxicity againstT. chilonis.Lufenuron and neem seed extract proved least toxic, methoxyfenozide and buprofezin were moderately toxic and pyripoxyfen exhibited the highest toxicity during the study. Similarly, lufenuron and neem seed extract proved less toxic for the adults, buprofezin was moderately toxic, and methoxyfenozide and pyripoxyfen exhibited the highest toxicity in the dipped surface assay after 4 h of exposure. All insecticides proved highly toxic for the adults 24 h after exposure. The results reveled that lufenuron and neem oil are relatively safe forT. chilonis.ConclusionsThe tested insecticides and neem seed oil exhibited varying degree of toxicity againstT. chilonis. The overall toxicity was classified as; pyriproxyfen > methoxyfenozide > buprofezin > lufenuron > neem seed extract. Therefore, neem seed extract and lufenuron are safer forT. chiloniscompared to the rest of the insecticides included in the study.
