Resistance Selection And Biochemical Mechanism To Deltamethrin In Spodoptera Exigua (Hübner)

Beet armyworm, Spodoptera exigua (Hiibner), is a worldwide distributed polyphagous pest on various cultivated crops, including vegetables, cotton, fruit trees, ornamentals and so on. In past two decades, Spodoptera exigua has emerged as a serious pest in many countries and it has been noticed that some population of Spodoptera exigua has became resistant to many insecticides including Pyrethroids, which result in many insecticides failed to control the pests. So far many scientists have being done some research in the resistance field, such as resistance monitoring, biochemical mechanisms for resistance, resistance evaluation, resistance inheritance etal. But the study encountered the difficult to the further stage for the absence of remarkable genetic strain.Spodoptera exigua resistant strain and mutant resistant strain to deltamethrin were respectively obtained by 12 generation laboratory selection. Their resistance increased by 17.78 and 11.94 times respectively. The resistance selection methods are population selection and single mating selection. The different processes in resistance selection between normal strain and mutant strain were studied.Spodoptera exigua susceptible strain was also obtained by single mating selection. After two generation selection, the LD₅₀ to deltamethrin of SEW decreased from 0.0081μg/larva to 0.0053μg/larva. The LD₅₀ to deltamethrin of SEM decreased from 0.0196μg/larva to 0.0079μg/larva. The sensibility of SEW and SEM to deltamethrin was not changed largely by two generation selection.Biochemical mechanisms of resistance in Spodopera exigua wild strains (SEW-R and SEW-S)and mutant strains(SEM-R and SEM-S) have been investigated by enzyme activities, including esterase, glutathioneS-transferase, MFO and phenoloxidase. The protective enzyme systems including superoxide dismutase (SOD), perxidase (POD) and catalase(CAT) were also analyzed in the four strains of Spodopera exigua .The results demonstrated that phenoloxidase ,esterase and MFO activities of Spodopera exigua wild and mutant resistant strain were higher than susceptible strain respectively. The activities of glutathione S-transferase and three protective enzymes did not have notable difference.