Responses of avermectin-resistant and susceptible strains of Neoseiulus cucumeris (Oudemans) (Acari: Phytoseiidae) to Tetranychus urticae Koch (Acari: Tetranychidae) on sweet potato

To identify the searching ability of avermectin-resistant and susceptible strains of Neoseiulus cucumeris (Oudemans), the responses of the two strains to stimuli from Tetranychus urticae Koch on sweet potato leaves were examined in the laboratory. The results showed that avermectin-resistant and susceptible adult N. cucumeris females responded to different stages and intact webs (spider mite, egg, feces, and leaf damage) of T. urticae, but not to the destroyed webs and feces of and feeding damage by T. urticae. Moreover, no significant differences were observed in the responses of the avermectin-resistant and susceptible strains of N. cucumeris. Both strains of N. cucumeris were often observed inside the intact webs of T. urticae. These results show that the avermectin-resistant and susceptible strains of N. cucumeris have the ability to search actively for T. urticae on sweet potato leaves. This behavior clearly increases the searching efficiency of N. cucumeris and may help its use in the biocontrol of T. urticae.