The rice stem borer,Chilo suppressalis(Walker),is a destructive pest of rice that is only capable of short-distance dispersal.This species exhibits marked differences in morphology and insecticide resistance among geographical locations,but the genetic basis for these variations is largely unknown.We examined the genetic variation of C.suppressalis at a fine spatial scale in 15 rice fields of southeastern China using expected heterozygosity and allelic richness.Elevation was the primary factor constraining gene flow and influenced population genetic structure.Geographical distance and mountain isolation were also significant variables associated with genetic divergence,whereas land use was less significant and the presence of a river 50 m wide had no effect on the genetic variation between adjacent populations.This fine scale study suggests that genetic variability of C.suppressalis populations should be considered when testing insecticides,considering the possible evolution of diverse ecotypes,each adapted to their own environmental conditions and selective pressures.Pest monitoring and management strategies should incorporate information on landscape genetics for optimal decision-making.