Cool down-warm up: Differential responses of stored product insects after gradual temperature changes

Authors: ATHANASSIOU, CHRISTOS - University Of Thessaly; Arthur, Franklin

Submitted to: Insects
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 2/4/2020
Publication Date: 3/1/2020
Citation: Athanassiou, C.G., Arthur, F.H. 2020. Cool down-warm up: Differential responses of stored product insects after gradual temperature changes. Insects. 11(3):158. https://doi.org/10.3390/insects11030158.
DOI: https://doi.org/10.3390/insects11030158

Interpretive Summary: Insects can develop a tolerance to cold temperatures and survive exposure if they have the opportunity to acclimate to the cold temperatures. There is interest in using cold temperatures to control stored product insects, but there is a need to determine low threshold temperatures that can be used in control strategies, and if pest species can acclimate to the threshold temperature. We conducted a study by setting a threshold temperature of 32°F, and determining if pre-or post acclimation to that temperature would lead to increased survival of adults of six stored product beetle species. For five of the six beetle species, acclimation had no effect on survival and the threshold temperature of 32°F was not low enough to kill the insects. The rice weevil was susceptible to the threshold temperature and mortality actually increased when beetles were allowed to acclimate. Results show that temperatures lower than 32°F must be used to control stored product beetles, and that acclimation may have little effect on eventual survival, except for the rice weevil, which is known to be a cold-tolerance species. Results also indicate that for optimal use of cold temperatures in control programs, specific time-temperature combinations may have to be developed for target pest species, due to the variability among species and life stages.

Technical Abstract: 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.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 scenario, and un-acclimated adults, had lower survival rates than those that had either exposed to pre-acclimation, or to both pre- and post-acclimation. Results 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 on survival of these species as well.