To acclimate or not to acclimate? Simultaneous positive and negative effects of acclimation on susceptibility of Tribolium confusum and Oryzaephilus surinamensis to low temperatures

Authors: ATHANASSIOU, CHRISTOS - University Of Thessaly; Arthur, Franklin; KAVALLIERATOS, NICKOLAS - Agricultural University Of Athens; HARTZER, KRIS - Centers For Disease Control And Prevention (CDC) - United States

Submitted to: Journal of Economic Entomology
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 4/26/2019
Publication Date: 10/1/2019
Citation: Athanassiou, C.G., Arthur, F.H., Kavallieratos, N.G., Hartzer, K.L. 2019. To acclimate or not to acclimate? Simultaneous positive and negative effects of acclimation on susceptibility of Tribolium confusum (Coleoptera: Tenebrionidae) and Oryzaephilus surinamensis (Coleoptera: Silvanidae) to low temperatures. Journal of Economic Entomology. 112(5):2441-2449. https://doi.org/10.1093/jee/toz136.
DOI: https://doi.org/10.1093/jee/toz136

Interpretive Summary: Cold temperatures can be used as a disinfestation strategy to manage stored product insects that can infest stored products. However, insects can acclimate to cold temperatures to some degree, which can increase the time it takes for mortality to occur at cold temperatures. However, there is little recent research data for acclimation ability of stored product insects. We conducted studies by allowing different life stages of the confused flour beetle and the sawtoothed grain beetle to acclimate to about 60°F for seven days then exposing them to sub-freezing temperatures. For both species, acclimation of adults increased their cold tolerance. Mixed results were obtained for larvae, but in general there was some level of acclimation. Exposure of non-acclimated and acclimated confused flour beetle 14°F for 1 day produced complete control of all life stages. Similarly, almost all non-acclimated and acclimated individuals of the sawtoothed grain beetle died when exposed to 14°F for 1 day. Consequently, this temperature-exposure combination can be proposed for practical utilization of cold treatments against both species. Managers of facilities where these insect species can infest stored products can use the data obtained in this study to develop management plans that take into account this susceptibility to cold and also factor in the effects of acclimation on cold tolerance.

Technical Abstract: Laboratory tests on acclimated and non-acclimated life stages of Tribolium confusum (adults, pupae, larvae, eggs) and Oryzaephilus surinamensis (adults, larvae, eggs), were conducted at 0, – 5, – 10 and –15°C to evaluate effects of acclimation on susceptibility to cold treatment. Acclimation of all tested life stages for 7 days at 15°C affected susceptibility of both species to the cold temperatures. After 1 day, at exposures = 2 h for both tested species, acclimated adults had a noticeable increase in cold tolerance compared to non-acclimated adults. Non-acclimated pupae of T. confusum were equally susceptible to cold compared to non-acclimated pupae at short exposures to low temperatures. Exposure of non-acclimated life stages of T. confusum, at – 10°C for 1 day gave 0% survival. Similarly, almost all non-acclimated individuals of O. surinamensis died at – 10°C. At 0°C, non-acclimated larvae were more cold-tolerant than acclimated larvae, but this trend was reversed when larvae were exposed to – 5°C. Mixed results were obtained for larvae of O. surinamensis because in some of the combinations tested, non-acclimated larvae were more tolerant, even at temperatures that were lower than 0°C. In contrast to O. surinamensis, eggs of T. confusum that had not been exposed to cold were not affected by acclimation, while exposure to cold showed increased cold hardiness in acclimated eggs. Results show that individual stored product insect species may have mixed susceptibility to cold temperatures, which must be taken into account when using cold treatment as a management strategy.