Cool Down-Warm Up: Differential Responses of Stored Product Insects after Gradual Temperature Changes

Insect survival after exposure to 0 °C for 7 days was examined in laboratory bioassays for control of adults of six major stored-product beetle species, Oryzaephilus surinamensis (L.), the sawtoothed grain beetle, Cryptolestes ferrugineus, (Stephens), the rusty grain beetle, Dermestes maculatus DeGeer, the hide beetle, Sitophilus oryzae (L.), the rice weevil, Tribolium castaneum (Herbst), the red flour beetle, and T. confusum Jacquelin DuVal, the confused flour beetle In this test there were four different acclimation treatments, insects that had been subjected to a pre-acclimation period to 0 °C, a post-acclimation period, both a pre and post-acclimation period, and adults that were not acclimated. Insect survival for all species except S. oryzae was not affected by the exposure to 0 °C, regardless of the acclimation scenario. In contrast, exposure to 0 °C drastically reduced survival of S. oryzae. Moreover, adults that were exposed to the post-acclimation only and un-acclimated adults had lower survival rates than those that had either exposure to pre-acclimation, or to both pre- and post-acclimation. Results of this experiment show that acclimation played a limited role in adult survival of five of the six tested species, and that exposure of adults to 0 °C for 7 d had no effect in survival of these species as well.