Biological Fitness of Different Insecticide Resistant Strains and Susceptible Strains Hybrids of Plutella xylostella

To explore the biological fitness variation of different insecticide resistant strains and susceptible strains hybrids,the relative biological fitness of P. xylostella were evaluated by constructing and comparing the life tables of three resistant strains (A) avermectin, (B) beta-cypermethrin, (D) thiosultap-disodium,the susceptible strain (S) and six F1 hybrid progenies from the reciprocal hybrids of the three resistant strains. The results revealed that the relative fitness value of the three resistant strains were 0. 72,0. 79 and 0. 59,respectively,which were lower than that of the susceptible strain (relative fitness value as 1. 0); and the relative fitness values of six F1 hybrid strains (A♀ +S♂,A♂ +S♀,B♀ +S♂,B♂ +S♀,D♀ +S♂ and D♂ +S♀) were 0.82,0.79,0.87,0.90,0.71 and 0.74,respectively,which were also lower than that of the susceptible strain,but were higher than that of the three resistant strains. This was beneficial for the development of resistant strains population of P. xylostella.