The fall armyworm, Spodoptera frugiperda (J. E. Smith), is one of the most important pests in tropical and subtropical regions of American. S. frugiperda was first detected in Southern China in January 2019, and then subsequently invaded in 26 provinces. Spinetoram widely used for pest management is recommended for S. frugiperda control. The sublethal effects of spinetoram on S. frugiperda were investigated in the present study. The toxicity of spinetoram against S. frugiperda larvae was determined after one oral dose of spinetoram at sublethal concentration. The results showed that spinetoram LC₁₀ and LC₃₀ were 0.011 and 0.044 mg/liter for the larvae, respectively. Spinetoram at sublethal concentration significantly increased developmental time but reduced larval body weight. In addition, spinetoram had a post-exposure effect on pupal weight, but not on pupal duration, pupation rate, emergence rate, eggs number, or adults longevity. In conclusion, the sublethal effects of spinetoram could negatively affect the growth and development of S. frugiperda that have important implications for pest management.

Pests are inevitably exposed to sublethal and lethal doses in the agroecosystem following the application of pesticides indispensable to protect food sources. The effect of spinetoram on amino-acid metabolism of fall armyworm, Spodoptera frugiperda (J.E. Smith), was investigated, at the dose of LC₁₀ and LC₉₀, by transcriptome and LC-MS/MS analysis. Using statistics-based analysis of both POS and NEG mode, a total of 715,501 metabolites in S. frugiperda were significantly changed after spinetoram treatment. The enhancement of glucose metabolism provides energy support for detoxification in larvae. The decrease in valine and isoleucine is associated with an increase in leucine, without maintaining the conservation of citric acid in the larvae. The down-regulation of phenylalanine may retard the tricarboxylic acid cycle to produce GTP. The abundance of lysine was decreased in response to spinetoram exposure, which damages the nervous system of the larvae. The abundance of arginine increases and causes non-functional contraction of the insect’s muscles, causing the larva to expend excess energy. Tryptophan provides an important substrate for eliminating ROS. The changes in glutamic acid, aspartic acid, and lysine cause damage to the nerve centers of the larvae. The results of transcriptome and LC-MS/MS analysis revealed the effects of pesticide exposure on amino-acid metabolism of S. frugiperda successfully and provide a new overview of the response of insect physio-biochemistry against pesticides.