Comparative population growth of the khapra beetle, Trogoderma granarium Everts and the warehouse beetle Trogoderma variabile Ballion on wheat and rice

Authors: LAMPIRI, EVAGGELIA - University Of Thessaly; BALIOTA, GEORGIA - University Of Thessaly; Morrison, William - Rob; DOMINGUE, MICHAEL - Animal And Plant Health Inspection Service (APHIS); ATHANASSIOU, CHRISTOS - University Of Thessaly

Submitted to: Journal of Economic Entomology
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 10/11/2021
Publication Date: 11/23/2021
Citation: Lampiri, E., Baliota, G., Morrison Iii, W.R., Domingue, M.J., Athanassiou, C.G. 2021. Comparative population growth of the khapra beetle, Trogoderma granarium Everts and the warehouse beetle Trogoderma variabile Ballion on wheat and rice. Journal of Economic Entomology. 115(1):344-352. https://doi.org/10.1093/jee/toab209.
DOI: https://doi.org/10.1093/jee/toab209

Interpretive Summary: The khapra beetle, which is ranked among the top 100 worst invasive species, is a pernicious pest and on the quarantined list in the United States (US). There have been an increasing number of interceptions of this species at ports of entry in the US, and the khapra beetle is generally viewed as devastating in countries where it occurs. However, there are a suite of closely related dermestids already in the US, including the warehouse beetle, which is a member of the same genus. In evaluating the baseline population growth of warehouse beetle and khapra beetle, we found they were similar to each other on wheat at 27 and 32°C. On rice, both also produced similar numbers of progeny at the higher temperature, but at 27°C khapra beetle did better over short storage periods, while warehouse beetle did better over longer storage periods. Both species caused equivalent commodity damage and generally produced similar amounts of frass (e.g. product contamination from biological processes). Our research suggests that under ideal conditions these two closely related, but very differently treated species in commerce from the same genus have comparable population growth, and cause similar damage on wheat and rice.

Technical Abstract: We evaluated the relative population growth of two stored-product insect species in the genus Trogoderma, the khapra beetle, Trogoderma granarium and the warehouse beetle, T. variabile. 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.