The effects of decreases in temperature on the survival, fecundity, egg hatching, and predation ability of Neoseiulus bicaudus (Wainstein) (Acari: Phytoseiidae)

Neoseiulus bicaudus (Wainstein), a predatory mite native to the Xinjiang Uygur Autonomous Region, China, is an effective predator against various crop pests such as spider mites, whiteflies, and thrips. Understanding the behavioral responses of N. bicaudus in response to temperature decreases during the autumn and winter seasons can help to evaluate the application range of the predatory mites as a biological control. The present study analyzed the survival rate, fecundity, egg hatching rate, and predation ability of N. bicaudus by examining the effects of temperature on female adults and eggs across a broad set of temperature gradients (30 ~ 20 °C, 25 ~ 15 °C, 20 ~ 10 °C, 15 ~ 5 °C, 10 ~ 0 °C, 5 ~ -5 °C, and 0 ~ -10 °C) (60 ± 10% RH). The results indicated that when the temperature gradient decreased to 10 ~ 0 °C, the seven-day survival rate of female adults of N. bicaudus began to decline; almost all female adults died when the temperature gradient further decreased to 0 ~ -10 °C. The fecundity of N. bicaudus gradually declined as the temperature decreased, and the mites ultimately ceased to lay eggs at a temperature gradient of 5 ~ -5 ℃. The hatching rate of N. bicaudus eggs decreased with the temperature decreased, eventually reaching 0% at 0 ~ -10 ℃. The predation ability of N. bicaudus for the prey Tetranychus turkestani (Ugarov et Nikolskii) gradually diminished as the temperature decreased, characterized by a reduced attack rate (a) and a concurrent progressive increase in the handling time (Th). When the temperature gradient decreased to 0 ~ -10 ℃, N. bicaudus terminated feeding activity. The survival rate, fecundity, egg hatching rate, and predation efficiency of N. bicaudus suddenly declined when the temperature gradient decreased to 0 ~ -10 ℃. The results suggest that the lowest winter temperatures will limit the overwintering population of N. bicaudus and that this predatory mite may successfully overwinter as eggs and female adults in temperatures above the 0 ~ -10 °C. In addition, the availability of food may be a crucial determining factor in the predatory mites’ choice of overwintering sites. This study provides data for the field application and conservation of N. bicaudus.