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

Abstract

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.