Sublethal effects of azadirachtin on lipid metabolism and sex pheromone biosynthesis of the Asian corn borer Ostrinia furnacalis

Abstract

Azadirachtin has remarkable toxic and growth inhibitory effects on Ostrinia furnacalis (Guenee) (Lepidoptera: Pyralidae). In this study, sublethal effects of azadirachtin on fatty acid metabolism and sex pheromone biosynthesis in O. furnacalis were investigated. Quantities of fatty acids were significantly reduced when larvae were fed a diet containing azadirachtin at 0.1–10 ppm. After 10 days, fatty acids were reduced by 50% on a diet treated with 10 ppm azadirachtin; the relative composition of fatty acids was also affected. The relative proportion of C18:2 fatty acid decreased significantly in adult survivors, correlating with decreased fecundity. Furthermore, sex pheromone titers in adults were inversely proportional to dietary azadirachtin concentration, and reduced by 50% relative to controls when larvae were fed a diet containing 10 ppm azadirachtin. However, there were no effects of azadirachtin on pheromone blend ratios. Our results suggest that reductions in fecundity and pheromone titer in O. furnacalis are associated with alterations in lipid metabolism by azadirachtin, although these effects are not linked to a reduction in consumption.