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.

The two spotted spider mite (TSSM) Tetranychus urticae is one of the most economically key mite pests of fields and greenhouse crops over the world. In order to clarify the control efficacy of Neoseiulus barkeri on Tetranychus urticae in the presence of entomopathogenic fungus (EPF) Acremonium hansfodii. This study was conducted to evaluate the control of combining N. barkeri with A. hansfodii against T. urticae. The results showed that the functional response of N. barkeri treated with Ahy1 strain to T. urticae was Holling type II equation. Among these, the highest predation number and the shortest attack time were obtained for the predator feeding on eggs, then followed by feeding on nymphs, female adults ranked as the lowest. That of N. barkeri to T. urticae treated with Ahy1 strain was also Holling type II equation. The predation capacity of N. barkeri on nymphs and female adults of T. urticae treated by Ahy1 strain increased with the increase of the concentration of Ahy1 strain, but that when feeding eggs had no significant difference. Therefore, the combination of EPF with N. barkeri on control of TSSM had synergistic effects, which will provide the guidance to carry out combined utilization of entomogenous fungi with predatory mites.

To study the physiological mechanisms of Neoseiulus barkeri in response to short-term heat stress, the eggs and the emerged adults were exposed to 38, 40, and 42°C, 85% ± 5%RH,16 h:8 h (L:D) for 2, 4, and 6 h. The activities of superoxide dismutase (SOD), peroxidase (POD), and catalase (CAT) as well as the protein content of N. barkeri were examined. All treatments caused significant different changes compared to the untreated control. The protein content increased as the temperature increased, while it showed different changing trends with the prolongation of exposure duration. The enzymatic activity of SOD, CAT, and POD was significantly affected by the temperature treatment. Both the maximum and minimum level of the three enzymes after a short-term heat stress differed significantly to the control group (p < 0.05). The highest values of three enzymatic activities were all obtained at 40°C-4 h. Person correlation analysis indicates that the high temperature was the primary factor affecting the enzymatic activity, while the exposure duration of the heat stress was the secondary factor. In general, the short-term heat stress increased the protein content of Neoseiulus barkeri and up-regulated the expression of SOD, CAT, and POD activities as well.

The spider mite Tetranychus urticae is one of the most economically key mite pests of fields and greenhouse crops over the world. In order to clarify the control efficacy of Neoseiulus barkeri on T. urticae in the presence of entomopathogenic fungus Acremonium hansfodii. This study was conducted to evaluate the control of combining N. barkeri with A. hansfodii against T. urticae. The results showed that the functional response of N. barkeri treated with Ahy1 strain to T. urticae was Holling type II equation. Among these, the highest predation number and the shortest attack time were obtained for the predator feeding on eggs, then followed by feeding on nymphs, female adults ranked as the lowest. That of N. barkeri to T. urticae treated with Ahy1 strain was also Holling type II equation. The predation capacity of N. barkeri on nymphs and female adults of T. urticae treated by Ahy1 strain increased with the increase of the concentration of Ahy1 strain, but that when feeding eggs had no significant difference. Therefore, the combination of EPF with N. barkeri on control of TSSM had synergistic effects, which will provide the guidance to carry out combined utilization of entomogenous fungi with predatory mites.