Synergistic effect of Bt (Cry1Ab + Vip3Aa) maize with emamectin benzoate and chlorantraniliprole against the fall armyworm, Spodoptera frugiperda

The invasion of the fall armyworm (FAW), Spodoptera frugiperda (J. E. Smith), has posed a serious threat to maize production in Africa and Asia. Chemical insecticides and Bt maize are the main means for FAW control, but the interaction between these two measures is also unclear. In this study, the susceptibility of the field population (Ezhou) fed on Bt maize insecticidal protein and the Vip3Aa-resistant population DH-R (206-fold) to emamectin benzoate (EB) and chlorantraniliprole (CAP) was determined by the topical application method. The results showed that the susceptibility of both populations to the two insecticides increased significantly. The mechanism is attributed to the inhibition of the activities of enzymes detoxification enzymes, including carboxylesterase (CarE), glutathione S-transferase (GSTs), and multifunctional oxidase (MFO). The corrected control effects of Bt (Cry1Ab + Vip3Aa) maize combined with EB or CAP against larvae were measured by a spraying method in the laboratory and field. The results showed that the combined use of Bt (Cry1Ab + Vip3Aa) maize and EB increased the corrected control effect by 22.70%-22.86% in the laboratory and 16.74% in the field. Similarly, the combined use of Bt (Cry1Ab + Vip3Aa) maize and CAP increased the corrected control effect by 54.92%-61.59% in the laboratory and 19.62% in the field. It is concluded that the Bt (Cry1Ab + Vip3Aa) maize and chemical insecticides (EB and CAP) have synergistic effects against FAW, providing a theoretical basis for integrating Bt maize with chemical insecticides to manage the FAW populations.