Insecticide resistance and its underlying synergism in field populations of Spodoptera frugiperda (J. E. Smith) from Hainan Island, China

The fall armyworm, Spodoptera frugiperda (J.E. Smith), is one of the most destructive grain pests worldwide since it gradually invaded Africa, Asia, and Australia. Chemicals serve as a useful tool for its management when there are S. frugiperda outbreaks. In the present study, insecticide resistance status and synergistic effects of gradual doses of three synergists-indoxacarb, chlorantraniliprole, and emamectin benzoate-were investigated. Compared with that in the relative susceptible strain, one population of S. frugiperda developed low levels of resistance at resistance ratio (RR) = 5.1-fold, five populations expressed minor resistance at 3.1-fold < RR < 4.2-fold, and 12 populations remained susceptible at 1.1-fold < RR < 2.8-fold to indoxacarb. To chlorantraniliprole, one population demonstrated low resistance at RR = 7.9-fold, two populations showed minor resistance at 3.9-fold < RR < 4.0-fold, and 15 populations remained susceptible at 1.1-fold < RR < 2.8-fold. Moreover, 18 populations remained susceptible at 0.9-fold < RR < 2.7-fold to emamectin benzoate. The maximum synergistic effects of indoxacarb, chlorantraniliprole, and emamectin benzoate were found for piperonyl buoxide at a dose of 80 mu g/individual along with synergistic ratios at 4.9-, 5.7-, and 7.5-fold, respectively. The results provide a comprehensive survey of insecticide resistance status of the field population in Hainan as well as the synergism of piperonyl butoxide (PBO), diethyl maleate (DEM), and triphenyl phosphate (TPP). Continued monitoring of insecticide resistance is recommended for the application of appropriate management tactics.

Automated summary

The study investigates the insecticide resistance status and synergistic effects of gradual doses of three synergists in the fall armyworm population in Hainan. The results show varying levels of resistance in different populations, with some populations showing improved insecticidal efficacy with higher doses. Continued monitoring and appropriate management strategies are recommended.