CONICET | Buscador de Institutos y Recursos Humanos

Abstract Rachiplusia nu is a defoliator lepidopteran species considered a potential pest in soybean and other crops. Cypermethrin is the main insecticide used in Argentina. Worldwide trends in pest control promote the use of insecticides with high specificity like methoxyfenozide; however, their usage in South America is still incipient. The effectiveness of cypermethrin and methoxyfenozide was studied on fifth larval instar of R. nu under chronic exposure in laboratory conditions. Four dilutions (between 10 and 80%) of the maximum field recommended concentration for each insecticide were assessed. Methoxyfenozide caused 100% larval mortality in all tested concentrations, while at tested cypermetrhin concentrations, larval mortalities were between 75 and 98%. Cypermethrin treatments showed higher mean survival time values than methoxyfenozide. Both insecticides inhibited larval growth according to weight loss assessment. Cypermethrin also inhibited diet consumption during the first 24 h exposure.