Published 2:11 pm Tuesday, May 13, 2025
Researchers who in 2024 discovered a new-to-Idaho beetle native to the Mediterranean basin aim to take more steps, such as increasing the sample size to develop stronger conclusions about presence and overall risk.
University of Idaho entomologist and extension specialist Armando Falcon-Brindis and his team last year confirmed darkling beetle larvae and adults after homeowners in Eagle and Emmett reported many larvae entering the homes. At the Eagle home, where the insects were mistaken for wireworms, the larvae — seeking places to pupate and overwinter — returned in abundance quickly despite repeated pest control treatments and frequent removal.
The researchers inspected inside and outside, including in yards and adjacent irrigated pastures. They did not find damage.
Where soil was extremely dry, testing confirmed nearly 30 darkling beetle larvae per square foot, according to a UI news release. Larvae densities were much lower in moister soil in the yard, and no larvae were found in samples from the irrigated farm field.
Based on testing and species-related research, Falcon-Brindis concluded the beetle prefers dry soils with abundant organic matter.
Falcon-Brindis, UI graduate student Henry Trujillo and UI Minidoka County Extension educator Jason Thomas published a paper about the beetle’s discovery in Idaho in the January 2025 issue of the journal Check List.
On farms, “I would say it is low risk,” Falcon-Brindis, the primary researcher, said in an interview. But farmers should watch for darkling beetles, particularly where little or no irrigation is used.
Now, “we can’t make any assumptions about the risk here or in the PNW,” he said. “But it is a fact that this species is established in California, Nevada and Idaho.”
Falcon-Brindis said he hopes to take a larger sample size to make stronger conclusions, look at the distribution of the beetle across Idaho, “and maybe down the road make some recommendations to control it along with some distribution modeling research.”
“Dryland farming areas in Idaho would be interesting to look at in the future,” particularly where the same crop is planted repeatedly, he said.
“We don’t know if changing environmental conditions would help it establish,” Falcon-Brindis said. “That requires more research.”
Another opportunity is to research the darkling beetle’s biology and how soil moisture impacts population thresholds, though it is unlikely the beetle will be a high priority for research since it does not appear to cause significant damage to crops, according to the news release.
The darkling beetle could become an urban pest, since it is still commonly misidentified, Falcon-Brindis told Capital Press.
The first observation of the darkling beetle in the U.S., was near the Sacramento River in California, according to research published in 2009.
How the beetle got to Idaho is not clear but might be attributed to agricultural trade, especially since many ranchers in the state’s southwest region buy California hay, according to the UI researchers’ recent paper.
