BOZEMAN — A team of researchers from Montana State University’s College of Agriculture published a paper earlier this month in the Journal of Insect Science outlining the risk of Asian giant hornets establishing populations in the Pacific Northwest, including Montana.
Recent graduate Erik Norderud, associate professor Scott Powell, and professor Bob Peterson of the Department of Land Resources and Environmental Sciences examined factors that may lead to higher risk for the insect’s establishment. The hornets have become known as “murder hornets” due to their status as a primary predator of honeybees. The team conducted risk assessments for every county in Idaho, Montana, Oregon and Washington — a total of 175 counties.
Asian giant hornets, or Vespa mandarinia, are the largest hornet species in the world. They were first detected in North America in Vancouver, British Columbia, and later in Whatcom County, Washington in late 2019. The first sighting of the insect in 2021 occurred in early August, also in Whatcom County in northwestern Washington. There have not yet been any confirmed sightings of the hornets in Montana.
“Asian giant hornets typically feed on insects, sap and soft fruits, but they are known to attack and kill beehives in the late summer and early fall when developing males and future queens need protein,” said Norderud, who graduated from the LRES professional master’s program in fall 2020 and is the lead author on the paper. “This behavior can affect beekeeping and pollination, and if the hornets become established, they could also displace native wasp species.”
Norderud now works with the USDA’s Animal and Plant Health Inspection Service, or APHIS, in Washington state. He said factors that make a county high-risk for hornet establishment are ideal temperature and suitable habitat. Asian giant hornet queens need an environment warm enough to survive the winter, but they also seem to be sensitive to very hot climates. Asian giant hornet queens also prefer green spaces for nest colonization, Norderud said, such as parks or forests.
The risk assessment for the study included factors such as forest cover, apiary locations and locations of ports and freight hubs in all 175 counties across those four states. Because the hornets are native to Asia, port locations were key as potential places where the insects could be introduced through trade coming from Asian countries.
The data was turned into maps of risk factors. Compiling the data allowed the team to see where the risk factors overlapped most, assigning each county an overall risk rating score, or ORS, classified as low, medium or high risk.
The team identified 32 counties across the four states as “low risk,” 120 as “medium risk,” and 23 as “high risk,” including Montana’s Lewis & Clark County, which received an ORS of 9 due to its large numbers of apiaries and high density of forest cover. Lewis & Clark was the only Montana county deemed “high risk” along with one county in Idaho, nine in Washington, and 12 in Oregon.
“This risk assessment is important because it helps professionals who are monitoring for this invasive species to prioritize areas where the hornet is more likely to establish,” said Peterson.
The best way to protect native pollinators and manage beehives, said Norderud, is to prevent the hornets from establishing in larger numbers in the Western U.S. He noted that some native hornets look similar to the invasive species, and that public involvement in monitoring the pollinators they see around their homes and towns is critical to identifying any Asian giant hornets in their communities.
“When the hornet was first found in the U.S. and reported in the media, there were reports from people all around the country claiming that they were finding them,” he said. “The interest and enthusiasm is great, but there are many native lookalikes which are important to the local ecosystem. Most importantly, I hope this publication will increase awareness of the threat Asian giant hornets can pose to essential pollinators in the U.S.”
The full paper, which includes lists and risk ratings for all 175 counties in Idaho, Montana, Oregon and Washington, can be read by clicking here.