The effects of short‐term heat stress on functional response of Neoseiulus barkeri to Tetranychus urticae

The predatory mite Neoseiulus barkeri (Acari: Phytoseiidae) is typically used for biocontrol of Tetranychus urticae on strawberries. However, its biological characteristics are greatly affected by temperature in hot summer days. In this study, the influence of different short‐term heat stresses on the functional response and prey consumption of unmated female of N. barkeri on three stages (egg, protonymph and adult) of T. urticae was evaluated. Three temperatures (38, 40 and 42°C), three short‐term heat duration (2, 4 and 6 hr), eight prey densities (3, 6, 9, 12, 15, 18, 21 and 24 individuals), (85 ± 5) % RH and a 16‐hr: 8‐hr (L:D) photoperiod were used during a 24‐hr period in functional response experiments. The results showed that the eggs of N. barkeri could not hatch at 42°C and the type II functional response was determined for adult females of N. barkeri at all treatments by using the logistic regression analysis. The N. barkeri had the highest attack rate of 1.029, 2.044 and 0.913 hr‐1 for three stages of T. urticae at 25°C and the lowest value of 0.585, 0.973 and 0.498 hr‐1 at 40°C, 6 hr. On the contrary, the handling time of the predator prolonged when the temperature increased from 25°C to 40°C and the maximum level was observed at 40°C, 6 hr (0.126, 0.153 and 0.172 hr). Our study indicated that the effects of short‐term heat stress were negative on the predation ability of N. barkeri and heat stress should be avoided as much as possible to achieve the best predation and control effect of N. barkeri in indoor rearing and field release.