Abstract: With the method of probit analysis, we estimated the realized heritability (h²) of resistance to fenitrothion in the rice stem borer (Chilo suppressalisWalker). The results demonstrated that tolerant phenotypes in the observed popula-tion are lowly heritable (h²=0.277) and that the population has no potential forhigher increase in tolerance to fenitrothion. Under the circumstances of laboratory selection, the population has to propagate about 6-12 generations to acquire 10-fold resistance to fenitrothion, and it takes a longer time (16-35 generations) for thefield population to do so. Our results suggest that the risk to developing high resistance to fenitrothion is small and thus, fenitrothion should be considered as an effective chemical agent in the system of insecticide resistance management for the rice stem borer.

Key words: Chilo suppressalis, insecticide resistance, fenitrothion, heritability, resistance risk assessment