Comparative Population Growth of the Khapra Beetle (Coleoptera: Dermestidae) and the Warehouse Beetle (Coleoptera: Dermestidae) on Wheat and Rice

We evaluated the relative population growth of two stored-product insect species in the genus Trogoderma, the khapra beetle, Trogoderma granarium Everts (Coleoptera: Dermestidae), and the warehouse beetle, Trogoderma variabile Ballion (Coleoptera: Dermestidae). Ten adults of each species were placed in vials containing wheat or paddy rice. These tests were performed at 27 and 32°C and the number of adults in the vials were counted after 35 and 70 days. For all the time intervals and temperatures of both species on wheat, the resulting larval abundances were similar, with the exception of 27°C at 70 days where more T. variabile larvae developed. At the higher temperature, both species had similar population growth on rice. However, the success was mixed at 27°C with T. granarium having a greater abundance after 35 days, while T. variabile dominated after 70 days. Frass production in both commodities was usually similar for the two species, but greater frass production occurred by T. variabile on wheat after 70 days at 27°C, while T. granarium produced more frass on rice after 35 days at 32°C. Both species nearly always caused equivalent commodity damage. Our research suggests that under ideal conditions these two closely, but very differently treated species in commerce from the genus Trogoderma have comparable population growth, and cause similar damage on wheat and rice.