Risk assessment and prediction of resistance to cypermethrin in housefly(Musca domestica)

  Objective   To assess resistance risk to cypermethr in and predict the rate of r esistance development in housefly(Musca domestica).

  Methods   Houseflies collected from natural group were cultured in laboratory.Resistant strain to cypermethrin in housefly was obtained while LD50 was deter mined with the method of topical application.Based on the method described by Tabashnik(1992), the realized heritability(h²)to cypermethrin in housefly was estimated and the rate of resistance development was predicted.

  Results   Continuously selected with cypermethr in for 10 generations at the average survival percentage of 54.5% in laboratory, the strain of housefly had a 50-fold increase in resistance to cypermethrin.The realized heritability(h²)of resistance to cyper methrin in housefly was estimated to be 0.157 7.The rate of resistance development for 10 fold in the housefly was predicted based on the estimation of the realized heritabilit y(h²), and it only needs 2.2-4.8 generations under the selected pressure of mortality ranged 50%-90%.

  Conclusion   The resistance to cypermethrin in housefly in creased rapidly and the realized heritability(h²)was stable in 10 generations.