Sublethal effects of insecticides on the predators, Podisus nigrispinus and Supputius cincticeps: Implications for IPM

Knowledge of the impact of insecticides on natural enemies is important for IPM programs. We assessed the toxicity and behavioral sublethal response of the predators, Podisus nigrispinus and Supputius cincticeps exposed to deltamethrin, methamidophos, spinosad and chlorantraniliprole. Concentration-mortality bioassays were carried out using soybean leaves immersed at different concentrations of each insecticide solution. After drying, the leaves were placed individually in Petri dishes, together with 10 third-instar larvae of Anticarsia gemmatalis or 10 third-instar nymphs of P. nigrispinus or S. cincticeps. Acute lethal toxicity was tested by placing 3^rd-instar nymphs on insecticide-impregnated filter paper. Two behavioral locomotory bioassays were carried out on 3^rd-instar nymphs of the predators – one using arenas fully-treated with insecticide and the other using half-treated arenas. Deltamethrin, methamidophos and spinosad caused 100% mortality of P. nigrispinus and S. cincticeps nymphs and, chlorantraniliprole proved to be most selective with low toxicity. Behavioral pattern changes were found for all pesticides, especially methamidophos and spinosad resulting in insecticide irritability in both predator species. However, insecticide repellence was not observed in any of the insects tested. Substitution of pyrethroid and organophosphate insecticides by chlorantraniliprole can be a key factor for the success of IPM programs of A. gemmatalis in soybeans.