Control of Trogoderma granarium (Coleoptera: Dermestidae) Using High Temperatures


Wilches, D.M., Laird, R.A., Floate, K.D., Fields, P.G. (2019). Control of Trogoderma granarium (Coleoptera: Dermestidae) Using High Temperatures. Journal of Economic Entomology, [online] 112(2), 963-968.

Plain language summary

Khapra beetle is one of the world’s most detrimental pests of stored grain. It is not present in Canada, but if introduced it will have a negative economic impact in the Canadian grain industry. The main method of control for khapra beetle has been fumigation with methyl bromide (MeBr), but this product is being removed from the market. As an alternative method of control, we evaluated the use of high temperatures. We first exposed different life stages (eggs, larvae, pupae, and adults) of khapra beetle to 45°C. Our results identified the most heat tolerant stage to be larvae in diapause (a state of dormancy where they do not actively feed or move), for which 50% of the individuals exposed died between 41-122 hours. We then tested the mortality of diapausing larvae at temperatures ranging from 45 to 60°C. At 60°C, 99% of the population died after exposing them for 1 hour. Based on our findings, exposure to 60°C for 2 hours should kill any khapra beetles that may be infesting a given commodity.


Khapra beetle, Trogoderma granarium Everts, is one of the world's most important pests of stored grain. Common in Africa and Asia, it is a quarantine insect for much of the rest of the world where methyl bromide has traditionally been used for its control. However, this ozone-depleting fumigant is now heavily restricted, and alternate methods of control are required. In a two-step process, we examined the use of high-temperature exposure as one such method of control. First, different life stages were held at 45°C for different periods to calculate LT 50 (lethal time to 50% mortality) values. In descending order, the most heat-tolerant life stages at 45°C were diapausing larvae (LT 50 = 41-122 h) > nondiapausing larvae (LT 50 = 47 h) > adults (LT 50 = 33 h) > pupae (LT 50 = 25 h) > eggs (LT 50 = 10 h). Second, diapausing larvae (the most heat-tolerant stage) were held at 45, 50, 55, and 60°C for different periods to calculate LT 50, LT 95, LT 99, and probit 9 (99.9968% mortality) values. Estimated LT 99 values for diapausing larvae were 288 h at 45°C, 6 h at 50°C, 1.1 h at 55°C, and 1 h at 60°C. Based on these results, an exposure of 2 h at 60°C is recommended to control T. granarium with high temperatures. To meet requirements for control of quarantine pests, exposure of between 2 and 12 h at 50-60°C is recommended to cause probit 9 mortality, but additional experiments are needed to get a better estimate of probit 9.