# Effects of Short-Term Heat Stress on the Development, Reproduction, and Demographic Parameters of Phytoseiulus persimilis (Acari: Phytoseiidae)

## TL;DR

This study shows how short-term heat stress affects the predatory mite Phytoseiulus persimilis, which is used to control spider mites in agriculture.

## Contribution

The research identifies specific temperature thresholds that impact the mite's development, survival, and reproduction under heat stress.

## Key findings

- Exposure to 42 °C prevented egg hatching and reduced adult longevity and reproduction.
- The best population growth of P. persimilis was observed at 36 °C.
- Short-term heat stress can threaten the effectiveness of this biocontrol agent in agriculture.

## Abstract

This study investigated how short-term exposure to high temperatures affects Phytoseiulus persimilis, a predatory mite widely used to control spider mite pests in agriculture. As climate change leads to more frequent and intense heat waves, understanding how such heat stress impacts both pests and their natural enemies is crucial. The research exposed mite eggs and adults to high temperatures for four hours and monitored their development, survival, and reproduction. The results showed that, while warmer conditions sped up development, extremely high temperatures (42 °C) prevented eggs from hatching. Adult mites also lived shorter lives and produced fewer offspring at higher temperatures, with the best population growth observed at 36 °C. These findings suggest that rising temperatures could reduce the effectiveness of this beneficial predator, potentially threatening pest control in crops. By identifying the temperature limits and optimal conditions for P. persimilis, this research provides valuable insights for future pest management strategies. It helps farmers and agricultural planners prepare for climate challenges and maintain sustainable, chemical-free crop protection.

Temperature is a critical factor affecting the development and population dynamics of many organisms. An organism’s ability to withstand extreme temperature events, such as heat waves, will become increasingly important as the severity, duration, and frequency of these events continue to rise worldwide due to global warming. Knowledge on the effects of heat stress on both pests and their natural enemies will thus be crucial for keeping biological control and pest control programs effective in future. This research aimed to study the effect of short-term heat stress on the predatory mite Phytoseiulus persimilis, which is one of the important natural enemies utilized as a biocontrol agent against spider mites such as Tetranychus urticae. The experiments assessed the immature developmental time of P. persimilis after a four-hour incubation of eggs at high temperatures, namely 36, 38, 40, and 42 °C, as well as 85 ± 5% RH and a 16:8 h photoperiod (L:D). After adult females emerged, they were exposed to the same conditions again and the population parameters were monitored. The results demonstrated that the immature development time decreased as temperature increased, with the shortest development duration of 5.30 days seen in eggs exposed to 40 °C, while the eggs exposed to 42 °C did not hatch. Female and male adult longevity decreased significantly as the temperature increased. Fecundity, the adult pre-ovipositional period, and the total pre-ovipositional period were lowest following the 40 °C treatment. The population parameters of P. persimilis, including r and λ, reached their highest values in mites treated at 36 °C, and were significantly higher than in the control group. Addressing these challenges through targeted research and adaptive management is essential to sustaining the efficiency of P. persimilis in biocontrol programs, particularly in the context of global climate change.