Suppression of Trehalase Activity by Validamycin Induces Mortality and Developmental Delays in Sitophilus zeamais (Coleoptera: Curculionidae)1

The maize weevil, Sitophilus zeamais Motschulsky (Coleoptera: Curculionidae), is a major pest of stored grains that feeds on and develops inside the grain. The trehalose analog validamycin has a strong inhibitory effect on insect trehalase. Studies have found that validamycin affects several insects; however, no information is available on its inhibitory and physiological effects on these insects. In this study, validamycin’s inhibitory effect on trehalase was examined by incorporating it into artificial seeds and feeding them to S. zeamais. Trehalase activity was recorded throughout the developmental stages of the exposed weevils and was highest in the larval followed by adult, pupal, and egg stages. We found that feeding adult S. zeamais artificial seeds containing validamycin resulted in a significant reduction of trehalase activity in both males and females, although the primary source of trehalase was in the intestinal tract rather than in the reproductive organs. The validamycin treatment also had a concentration-dependent lethal effect, resulting in approximately 90% mortality, with females being more susceptible than males. In addition, the validamycin treatment caused a significant reduction in the number of first-generation progeny and S. zeamais demonstrated delayed development in a concentration-dependent manner. These data show that validamycin influences trehalase enzyme activity, reproductive success, and development of S. zeamais. The results obtained from this research will be valuable tools for designing a control strategy.