Improvement in the cold storage of Aphidius ervi (Hymenoptera: Aphidiinae)

Biological control is beginning to be more commonly used, especially in greenhouses. The inundatory release of insects, especially parasitoids, requires a thorough knowledge of their biology and of mass-rearing techniques. Moreover, to synchronize releases with host presence, the parasitoids have to be kept in cold storage. However, cold storage may lead to a decrease in the viability of the parasitoids, in particular their survival, mobility and sex ratio. The aim of this study was to determine the best temperature at which to keep parasitoid mummies in cold storage. The parasitoid Aphidius ervi Haliday (Hymenoptera, Braconidae) and two of its host aphids, Sitobion avenae and Acyrthosiphon pisum, were used. It is concluded that the mummies can be kept for a maximum of two weeks at 7 °C without emergence of adults and for seven weeks at 2 °C without emergence or mortality. Moreover, storage of the mummies at 7 or 2 °C does not affect fertility. However, parasitoid pupae in A. pisum mummies suffered a higher mortality and took longer to complete their development. The practical implications of these results are discussed.