Optimizing temperature and humidity for Pyemotes zhonghuajia reproduction and survival: implications for mass-rearing and field release

The ectoparasitic mite Pyemotes zhonghuajia Yu, Zhang & He (Aricae: Pyemotidae) is an efficient biological control agent against pests from various orders, but the environmental factors influencing its reproductive performance remain poorly understood. This study investigated the combined effects of temperature (17–33 °C) and relative humidity (20–90% RH) on the reproductive traits and survival of P. zhonghuajia females. Results reveal that increasing temperature significantly shortened the longevity; while the pre-oviposition period and oviposition period decreased with increasing temperature with no significant difference detected between 29 °C and 33 °C and between 25 °C and 29 °C, respectively. Fecundity peaked at 21 °C before decreasing at higher temperatures. Humidity played a secondary role, with offspring production gradually increasing when humidity rosed up to 80% RH at 17–29 °C, although increasing humidity offered limited mitigation against thermal stress at 33°C. The lower and upper thermal thresholds for reproduction were estimated at 11.56–12.93 °C and 33.41–33.46 °C, respectively, and were not affected by humidity. A high temperature of 33 °C significantly reduced both fecundity and the proportion of female offspring. The study delivers knowledge for practical guidelines for large-scale commercial mass-rearing (21 °C, 80% RH) and highlights the importance of avoiding field augmentative releases during periods of high temperatures to maximize the effective pest control.