Steps towards the cryopreservation of the biological control agent Aphidoletes aphidimyza Rond (Diptera, Cecidomyiidae)

The eggs of an innately cold intolerant biological control agent, Aphidoletes aphidimyza Rond., were chemically permeabilised and successfully maintained in a culture medium. High survival of the embryos was achieved after loading and unloading of 3 M methanol and 2 M glycerol but there was no survival of cryoprotectant-loaded embryos following slow cooling protocols. The absence of intra-embryonic ice formation (revealed by cryomicroscopy) suggests that mortality was due to chilling injury. A very small number of embryos survived rapid cooling (to -196 degrees C) and warming after loading with 2 M glycerol, and developed to adult; however, this result could not be repeated. It was thought that embryo age was a critical factor in obtaining survival but this variable could not be easily controlled.