Rapid cold hardiness response and its ecological costs in Cabbage aphid Brevicoryne brassicae (Hemiptera: Aphididae)

Rapid cold hardiness in response to sudden decline in air temperature plays an important role in the aphid survival. Rapid cold hardiness is a phenomenon that increases insect’s survival at sub-zero temperatures following a brief exposure to low temperatures above ۰ °C. In this regard, the cabbage aphid Brevicoryne brassicae (L.) is able to increase its cold hardiness gradually during cold season and produce large population on host plants in Brassicaceae family. In this research, rapid cold hardiness of B. brassicae, and its effects on development time, longevity and fecundity were investigated. Direct transfer of aphids from ۲۰ °C to a series of sub-zero temperatures for ۲ h, resulted in a LT۸۰ (estimated temperature required to kill ۸۰% of tested population) of -۷.۳ °C. Preconditioning of first instar nymphs for ۳ h and adults for ۲ h at ۰ °C resulted in the highest survival rates of ۶۳% and ۷۱%, respectively. Acclimation of aphids, by a cooling rate of ۰.۰۵ °C/min form ۲۰ to ۰ °C, prior the exposure to LT۸۰ (-۷.۳ °C) resulted in the highest survival. No detrimental effects of rapid cold hardiness were observed on development time, longevity and fecundity. Results of the present study showed that rapid cold hardiness is induced in B. brassicae and increases the aphid survival in response to unexpected changes of temperature.