The Fitness of Metaseiulus occidentalis (Acari: Phytoseiidae) Adult Females after Different Intervals of Storage at Low Temperatures

Abstract

This study was carried out to determine the effects of temperature, relative humidity (RH), and an additional food source (honey) on the survival of Metaseiulus occidentalis (Nesbitt) (Acari: Phytoseiidae) females under cold-storage conditions. Survival was evaluated after 2, 4, and 8 wk at 7 or 10 °C under 75 or 95% RH. At the end of each cold-storage interval, surviving females were transferred to bean leaf discs with Tetranychus urticae Koch (Prostigmata: Tetranychidae) as prey, and their longevity, total number of eggs, and number of eggs each female produced per day were recorded. The highest survival rate (78.3%) was observed after 2 wk at 10 °C and 95% RH without honey in the tube. Survival was next highest (75%) after 2 wk at 7 °C and 95% RH without honey in tube. Survival was 76.7% at 7 °C with 95% RH without honey after 4 wk. Survival was low after 8 wk at both 7 or 10 °C, with 0 and 13.3% survival, respectively, at 95% RH. Adult longevity, the total number of eggs deposited, and the average number of eggs per female per day were not significantly different between females held for 2 or 4 wk at 7 or 10 °C at 95% RH with or without honey. Based on these results, M. occidentalis can be cold stored at 7 and 10 °C at 95% RH for up to 4 wk, but adding honey provided no benefit to the females.