Abstract  [Objectives]  To determine the gustatory electrophysiological and behavioral responses of the fall armyworm Spodoptera frugiperda to three plant secondary metabolites; rotenone, azadirachtin and matrine, and thereby provide a basis for the environmentally-friendly control of this important pest. [Methods]  Gustatory electrophysiological responses were measured by single sensillum recording whereas behavioral responses were determined using a dual-leaf-disc choice assay. In addition, the leaf-dipping method was used to investigate the lethality of the three plant secondary metabolites to first, second and third instar larvae. [Results]  The medial sensillum styloconicum on the maxillary galea of S. frugiperda caterpillars has a gustatory receptor neuron (GRN) sensitive to rotenone, whereas the lateral sensillum on the maxillary galea has GRNs sensitive to matrine and azadirachtin. Certain concentrations of rotenone, azadirachtin and matrine inhibited feeding by larvae with azadirachtin having the strongest inhibitory effect, inhibiting feeding even at relatively low concentrations. Chemical agents of the three plant secondary metabolites had significant lethal effects on larvae; 6.0% rotenone and 0.3% azadirachtin (120 dilution ratio) caused 100% and 74.3%, respectively, mortality in first instar larvae. [Conclusion]  The plant secondary metabolites rotenone, azadirachtin and matrine, clearly suppress feeding by S. frugiperda larvae. This is consistent with the gustatory responses of the GRNs of larvae to these compounds, and their high lethality to first instar S. frugiperda larvae.