Acute toxicity and sublethal effects of methoxyfenozide and thiodicarb on survival,development and reproduction of Helicoverpa armigera (Lepidoptera: Noctuidae)

The cotton bollworm Helicoverpa armigera (Hubner) is one of the most destructive pest insects in Iran and many other countries. In this study, lethal and sublethal effects of methoxyfenozide, and thiodicarb were evaluated against H. armigera larvae that fed on insecticide-treated artificial diet. The effects of methoxyfenozide and thiodicarb were assessed in 3rd instars. Methoxyfenozide and thiodicarb showed LC₅₀ values of 4 and 639 mg a.i./ml, respectively, in H. armigera larvae. Sublethal effects on development, adult longevity, and reproduction were observed in H. armigera larvae that survived exposure to an LC₃₀ of the insecticides. Larvae that were exposed to an LC₃₀ concentration of methoxyfenozide exhibited lower pupal weight and increased larval and pupal developmental times compared with thiodicarb treated larvae or control larvae. Adults that were exposed as larvae to an LC₃₀ concentration of methoxyfenozide or thiodicarb showed reduced fecundity (35% and 30%, respectively) compared to control adults. The tested insecticides significantly reduced adult longevity. The longevity of adult females that as larvae were treated with an LC₃₀ concentration of methoxyfenozide or thiodicarb was reduced by 28% and 23%, respectively, in comparison to control females. We predict that the combination of lethal and sublethal effects of the insecticides, especially methoxyfenozide, will induce significant effects on field population dynamics of H. armigera.