Laboratory and Semi-Field Evaluation of Selected Insecticides Against the Tobacco Caterpillar, Spodoptera litura (Lepidoptera: Noctuidae) in Cocoa

Cocoa (Theobroma cacao Linnaeus) is an important commercial crop widely cultivated in humid tropical regions. The recent occurrence of Spodoptera litura on cocoa has been found to cause significant damage to nurseries and open fields. Chemical approach is an important management strategy to control lepidopteran pests on a short-term basis. In this context, we tested the efficacy of seven synthetic insecticides belonging to five chemical groups; cyantraniliprole + lufenuron and chlorantraniliprole (diamides), spinetoram and spinosad (spinosyns), emamectin benzoate (avermectins), indoxacarb (oxadiazine) and fipronil (phenylpyrazole), on eggs and larval stages (second and fourth instar) of S. litura under laboratory and semi-field conditions. The results showed that the egg and second instar S. litura larvae were more susceptible to the tested insecticides. Of these, the mixture of cyantraniliprole + lufenuron and emamectin benzoate was found to be the most effective and their LC50 values were 0.03, 0.41 and 0.60, 2.28 mg a.i L-1 on eggs and second instar larvae, respectively. Further, cyantraniliprole + lufenuron and emamectin benzoate caused larval mortality of 93.3 and 83.4%, followed by chlorantraniliprole (78.4%) under semi-field conditions; while, fipronil and indoxacarb were relatively less toxic while other insecticides showed moderate effect against S. litura larvae.