Effects of extreme temperatures on the survival of the quarantine stored-product pest, Trogoderma granarium (khapra beetle) and on its associated bacteria

Citation

Wilches, D., R.A. Laird, K.D. Floate and P. Fields. 2017. Effects of extreme temperatures on the survival of the quarantine stored-product pest, Trogoderma granarium (khapra beetle) and on its associated bacteria. Joint Annual Meeting of the Entomological Society of Canada / Entomological Society of Manitoba, Winnipeg, Manitoba, Canada, October 22-25 [oral presentation]

Résumé

Trogoderma granarium is a pest of stored-grain products in Asia and Africa, and a quarantine pest for much of the rest of the world. To evaluate extreme temperatures as a control strategy for this pest, I investigated the effect of low temperatures on the survival and on the microbiome of T. granarium. The cold tolerance of T. granarium was assessed by measuring the supercooling points (SCP) of different life stages. The lowest SCP for larvae, 24.3 ± 0.3°C, was obtained for diapausing-acclimated larvae. According to LT50 values, the most cold tolerant stage at 10°C, was the diapausing-acclimated larvae (87 days, CI = 78-97 days). In light of the long exposure time needed to control T. granarium even at 20oC, cooling to below 27oC (i.e., below the SCP of eggs) will quickly kill all life stages and may be the best way to control this insect with low temperatures. The microbiome of T.granarium seems to be dominated by Spiroplasma bacteria. The microbiome was affected by life stage, but an effect of low temperatures was not detected. Further research is necessary to understand the Spiroplasma-T. granarium relationship. Future research should also investigate combinations of extreme temperatures with other techniques to shorten the time required for mortality.