Responses of biological characteristics and detoxification enzymes in the fall armyworm to methoxyfenozide stress

Methoxyfenozide is an insecticide with a unique mode of action on the insect ecdysone receptor and has been registered for the control of insect pests all over the world. In the present work, Spodoptera frugiperda was exposed to sublethal and lethal concentrations of methoxyfenozide to determine its impact on specific biological traits, metabolic enzyme activity, and the expression of detoxification enzymes. The result showed that 72-h posttreatment with LC50 and LC70 of methoxyfenozide significantly reduced the fecundity (eggs/female) of the F0 generation compared to those of the control group. However, the duration of the prepupal period was significantly increased. The exposure to LC10, LC30, LC50, and LC70 concentrations of methoxyfenozide significantly extended the developmental duration of larvae in F1 individuals. The fecundity of the F1 generation was significantly decreased, and the population life table parameters of F1 were also significantly affected. The activity of carboxylesterases showed little significant change, whereas the activity of glutathione S-transferases (GSTs) and cytochrome P450 monooxygenases (P450s) was significantly altered after exposure to LC10, LC30, LC50, and LC70 of methoxyfenozide. In total, 24-, 48-, and 96-h posttreatment with LC10, LC30, LC50, and LC70 of methoxyfenozide could cause upregulation of P450 genes such as CYP6AE44, CYP6B39, CYP9A26, CYP9A58, CYP9A59, and CYP9A60, as well as GST genes including GSTe3, GSTe9, GSTe10, GSTe15, GSTo2, GSTs1, GSTs5, GSTm2, and GSTm3. These findings could be instrumental in elucidating the molecular mechanisms underlying the sublethal and lethal effects of methoxyfenozide to S. frugiperda.