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

Abstract

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 high and low temperatures on the survival (Chapters 2 and 3) and on the microbiome (Chapter 4) of T. granarium. The most cold- and heat-tolerant life stages were diapausing-acclimated larvae and diapausing larvae, respectively. Trogoderma granarium can be controlled (Probit 9) with an exposure of 70 d to −15°C or 1.2 h to 60°C. High temperatures affected the microbiome; an effect of low temperatures was not detected. While the microbiome changed with life stage, it was dominated by Spiroplasma bacteria. 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.