Jing Shi1, Lan Zhang, Xiwu Gao. 1. Department of Entomology, China Agricultural University, Beijing, China.
Abstract
BACKGROUND: Spinosad, a relatively new, effective and safe pesticide, has been widely used in pest control over the last 10 years. However, different levels of resistance to this insecticide have developed in some insects worldwide. RESULTS: After continuous selection for 27 generations, a strain (SpRR) of the housefly developed 247-fold resistance to spinosad compared with the laboratory susceptible strain (CSS). The estimated realised heritability (h(2) ) of spinosad resistance was 0.14. There was no significant difference in the LD(50) values and slopes between reciprocal progenies F(1) and F(1) ', and values of 0.33 (F(1) ) and 0.30 (F(1) ') were obtained for the degree of dominance. Chi-square analysis from responses of self-bred (F(2) ) and backcrosses (BC(1) and BC(2) ) were highly significant, suggesting that the resistance was probably controlled by more than one gene. Synergists piperonyl butoxide (PBO), diethyl maleate (DEM) and S,S,S-tributyl phosphorotrithioate (DEF) affected the toxicity of spinosad at a low level, and demonstrated that metabolic-mediated detoxification was not an important factor in conferring resistance to spinosad in the SpRR strain. CONCLUSION: It was concluded that spinosad resistance in the housefly was autosomal and incompletely dominant, and the resistance was probably controlled by more than one gene. These results provide the basic information for designing successful management programmes for the control of houseflies.
BACKGROUND: Spinosad, a relatively new, effective and safe pesticide, has been widely used in pest control over the last 10 years. However, different levels of resistance to this insecticide have developed in some insects worldwide. RESULTS: After continuous selection for 27 generations, a strain (SpRR) of the housefly developed 247-fold resistance to spinosad compared with the laboratory susceptible strain (CSS). The estimated realised heritability (h(2) ) of spinosad resistance was 0.14. There was no significant difference in the LD(50) values and slopes between reciprocal progenies F(1) and F(1) ', and values of 0.33 (F(1) ) and 0.30 (F(1) ') were obtained for the degree of dominance. Chi-square analysis from responses of self-bred (F(2) ) and backcrosses (BC(1) and BC(2) ) were highly significant, suggesting that the resistance was probably controlled by more than one gene. Synergists piperonyl butoxide (PBO), diethyl maleate (DEM) and S,S,S-tributyl phosphorotrithioate (DEF) affected the toxicity of spinosad at a low level, and demonstrated that metabolic-mediated detoxification was not an important factor in conferring resistance to spinosad in the SpRR strain. CONCLUSION: It was concluded that spinosad resistance in the housefly was autosomal and incompletely dominant, and the resistance was probably controlled by more than one gene. These results provide the basic information for designing successful management programmes for the control of houseflies.