Effect of low temperature and short day length exposure on the development of Aphidius gifuensis Ashmead (Hymenoptera: Braconidae)

Abstract

Developmental responses of an indigenous aphid parasitoid, Aphidius gifuensis were compared when incubated at a low or high temperature and a short or long day length. Host aphid mummification and parasitoid emergence from mummies were observed with very high probabilities of over 80% and 90%, respectively, at all treatments. Sex ratios of emerged parasitoids remained constant at approximately 0.6. Developmental periods of parasitoid progenies reared with a short day length were approximately equal to those with a long day length for both sexes, although the duration from mummy to emergence at 15°C significantly differed between short and long day lengths. These results were summarized as A. gifuensis complete development under low temperature and short day length conditions of 15°C and 10L-14D instead of entering larval diapause as mummies. We thus conclude that A. gifuensis populations introduced into domestic greenhouses can increase and work effectively as biological control agents against pest aphids even during the hibernal season with low temperature and short day length conditions.