Effects of a short-term heat stress on the functional response of Scolothrips longicornis to Tetranychus urticae.

Biological control employing predatory insects represents an environmentally sustainable approach for suppressing two-spotted spider mite populations in both greenhouse and open-field cropping systems. In the present study, a laboratory experiment was performed to assess the functional response and predation efficiency of the predatory thrips Scolothrips longicornis (Thysanoptera: Thripidae) feeding on eggs of the two-spotted spider mite, Tetranychus urticae (Acari: Tetranychidae), with particular emphasis on the influence of short-term heat stress. Functional response assays were conducted over a 24-h period under three temperature regimes (38°C, 40°C, and 42°C), three durations of short-term heat exposure (2, 4, and 6 h), seven prey densities (10, 20, 30, 40, 50, 60, and 70 individuals), a relative humidity of 60 ± 10%, and a 16:8 h (L:D) photoperiod. The results showed that S. longicornis eggs failed to hatch at 42°C. Logistic regression analysis further revealed that adult females of S. longicornis exhibited a type II functional response under all experimental treatments. The highest attack rate on T. urticae eggs was recorded at 25°C (0.0506 h-1), whereas the lowest value (0.0367 h-1) occurred following exposure to 40°C for 6 h. In contrast, handling time increased progressively with rising temperature from 25°C to 40°C, reaching its maximum at 40°C after 6 h of heat exposure (1.1467 h). These findings indicate that short-term heat stress adversely affects the predatory performance of S. longicornis. Therefore, exposure to heat stress should be minimised to maximise its predation efficiency and biological control effectiveness during both mass rearing and field release.