Increasing global risk of khapra beetle invasion forecasted under projected environmental conditions

Authors: HARMON, RACHEL - Orise Fellow; Morrison Iii, William; ALTUNC, YUNUS - Ordu University; ATHANASSIOU, CHRISTOS - University Of Thessaly; Gerken, Alison

Submitted to: Scientific Reports
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 7/11/2025
Publication Date: 7/18/2025
Citation: Harmon, R.R., Morrison Iii, W.R., Altunc, Y.E., Athanassiou, C.G., Gerken, A.R. 2025. Increasing global risk of khapra beetle invasion forecasted under projected environmental conditions. Scientific Reports. 15. Article number 26064.. https://doi.org/10.1038/s41598-025-11690-8.
DOI: https://doi.org/10.1038/s41598-025-11690-8

Interpretive Summary: The khapra beetle is an invasive stored product pest of global concern that was previously eradicated from the US in the 1960s at a cost of >$120 million USD. However, risks of reinfestation in US and in other countries where khapra beetle has been eradicated are still high as it is easily transported in grain shipments. The pest has been reported in over 60 countries, several of which have spent millions USD to eradicate populations. Despite this risk, it is not known where this insect could establish and how temperature and precipitation influence habitat suitability. We modeled habitat suitability using current climatic conditions to predict future areas of habitat suitability under low and high temperature change scenarios at close (2040) and distant (2080) time points. Our model achieved higher accuracy when data from both native populations and introduced populations were included. This is important because many species distribution models are based only on native populations, which can underestimate suitability. Areas with higher potential suitability are projected to increase over time, primarily in North America and Europe, which have previously eradicated khapra beetle. In addition, areas of high suitability were associated with higher precipitation and higher minimum temperatures of coldest months. These areas need the greatest surveillance as much expansion is inland toward areas of high grain production.

Technical Abstract: The khapra beetle, Trogoderma granarium, is a stored product pest of global concern. The pest is readily transported with cargo and has been reported in over 60 countries, several of which have spent millions in USD to eradicate populations. Despite the profound risk to stored grain commodities, nothing is known about the influence of climate change on the potential future distribution of species. We utilize MaxEnt and two datasets representing 1) only the historical range and 2) all global locations where it currently is or was established even if it was later eradicated, termed accumulated data, to model areas of suitability under current climatic conditions and project to the future with the accumulated data under low (SSP126) and high (SSP585) climate change scenarios at close (2040) and distant (2080) time points. The potential distribution using the historical data was much reduced compared to the accumulated model; consequently, all established localities, even if eradicated, will change the model outcomes and thus may be important when building models. An increase of high potential suitability (>75% suitable) is projected with greater time and climatic scenarios, primarily in North America and Europe, which have previously eradicated T. granarium. These areas need greater surveillance for early detection and eradication to prevent the expansion of T. granarium inland toward areas of high grain production.