Abstract: To examine the difference in functional response of Neoseiulus barkeri to Tetranychus urticae between the mixed pesticide resistant strain and susceptible strain, the predation of N. barkeri on three stages (egg, nymph and female adult) of the two strains of T. urticae was examined at five temperatures (16, 20, 24, 28 and 32 ℃) and (75±5)% RH under the laboratory condition. The results showed that predatory functional responses were in fitted well with Holling Ⅱ equation. at 16－28 ℃, attack index (a), the a/T_h value, the maximum predatory number (1/T_h) increased, and the average treatment time decreased with increase in temperature, reaching the maximum at 28 ℃. The maximum predatory number of female adults, nymphs and eggs of the resistant prey was 7.6, 14.5, 16.0, respectively, and of the susceptible prey, 7.9, 18.3, 20.1, respectively. The treatment time of the three prey stages was 0.132 d, 0.069 d, and 0.062 d for the resistant strain, respectively, and 0.126 d, 0.055 d, and 0.050 d for the susceptible strain, respectively. the maximum predatory number was reduced with temperature reaching 32 ℃. And the predatory capacity of N. barkeri to the susceptible strain was significantly higher than to the mixed resistant strain at a certain temperature (P<0.05). We suggest rotation use of insecticides to protect predatory mites and to avoid or delay pesticide resistance development in T. urticae.

Key words: predator function, Tetranychus urticae, susceptible strain, mixed pesticides resistant strain, Neoseiulus barkeri