Responses of Tribolium castaneum life stages to elevated temperatures

Heat treatment involves raising the temperature of food-processing facilities to 50-60oC to kill stored-product insects. Of all the stored-product insects, the red flour beetle, Tribolium castaneum (Herbst), is the most frequently encountered insects and one for which structural treatments, such as heat treatment, are applied. However, very little is known about the influence of food products or sanitation on susceptibility of various life stages (eggs, young larvae, old larvae, pupae, and adults) of T. castaneum to elevated temperatures. In this paper, we present results from three heat treatments conducted in a pilot scale flour mill at Kansas State University, where sanitation levels were simulated in bioassay boxes and various life stages of T. castaneum, and in PVC rings with adults and eggs of T. castaneum. In general, both these tests have shown that the susceptibility of various T. castaneum life stages was influenced by how quickly temperatures reached 50oC, how long temperatures were held above 50oC and the maximum temperature. The protective effects of sanitation were evident only if temperatures did not reach 50oC or when temperatures above 50oC were not held for ≥ 2 h. Our results conclusively showed that the life stages of T. castaneum can be effectively managed during a 24 h heat treatment provided the lethal temperatures (50-60oC) are attained and maintained for several hours between 50 and 60oC.