Azadirachtin inhibits the development and metabolism of the silk glands of Spodoptera frugiperda and affects spinning behaviour

Abstract Spodoptera frugiperda is a major agricultural pest, and the 1st -3rd instar S. frugiperda have spinning behaviour and can drift to adjacent plants with the help of the wind. The present study found that azadirachtin can affect this behaviour, and the mechanism by which azadirachtin affects the spinning behaviour of S. frugiperda has been studied. In this study, the 3rd instar larvae were exposed to azadirachtin, and the pathological changes in the silk glands of S. frugiperda and the differences in their metabolites were analysed by pathological sectioning, transmission electron microscopy, metabolomics and other experimental methods. The results showed that azadirachtin can affect the silk gland of S. frugiperda. After 48 h of treatment with azadirachtin, the silk gland lumen of S. frugiperda appeared vacuolated, and KEGG showed that 31 different metabolites were identified, of which 12 were upregulated and 19 were downregulated. These metabolites were enriched in 15 different metabolic pathways, which pathways indicated that the silk gland of S. frugiperda was closely related to the formation of fatty acids and to energy metabolism in the process of silk formation. This research can further explain the spinning mechanism of insects and provide a research basis for determining the spinning, cocooning, and transfer damage mechanisms of many agricultural and forestry pests.