Effects of Tomato Water Stress on the Life-History and Population Parameters of the Predatory Thrips Scolothrips longicornis

Increasing drought occurrence under climate change is expected to alter ecological interactions in agroecosystems, with important implications for biological control. Drought can alter plant–herbivore interactions and thereby affect the performance of natural enemies through bottom-up effects. However, the demographic consequences of drought-induced changes in host plants for predatory thrips remain poorly understood. We investigated the effects of three soil moisture treatments of tomato plants on the life-history and demographic performance of the predatory thrips Scolothrips longicornis Priesner feeding on Tetranychus urticae Koch eggs under constant abiotic conditions (25 ± 1 °C, 65 ± 5% RH, and a 16L:8D photoperiod) in a controlled-environment growth chamber. The plants were maintained under 100% field capacity (100% FC), moderate water stress (70% FC), or severe water stress (50% FC). The soil moisture treatment significantly affected the duration of the egg stage but not that of other immature stages and did not have an effect on pre-adult survival. In contrast, severe water stress significantly reduced female and male longevity. Reproductive performance showed a nonlinear response to water availability. Females under 70% FC had significantly higher fecundity and a longer oviposition period than females under 100% FC or severe water stress. The net reproductive rate was the highest under 70% FC and differed significantly from both 100% FC and 50% FC. Similarly, the intrinsic rate of increase, finite rate of increase, and mean generation time were significantly affected by treatment. Overall, moderate water stress maintained or enhanced several fitness-related traits of S. longicornis, whereas severe water stress reduced adult longevity and reproductive performance. These findings demonstrate that plant-mediated effects of drought on predatory thrips are nonlinear and highlight the importance of plant water status in determining the demographic potential of natural enemies and their effectiveness in biological control programs for water-limited tomato production systems.