A $4.2 million, four-year study will focus on a disease killing honeybees and affecting the pollination of specialty crops such as blueberries.

Oregon State University will lead the project on European foulbrood disease in partnership with Washington State University, University of California-Davis and Mississippi State University.

Funding is from the USDA National Institute of Food and Agriculture.

European foulbrood disease is caused by a bacteria that infects honeybees at the larval stage, turning newly hatched larvae into brown mush within a few days.

“It used to be a minor problem in the past, but for the last six or seven years, it has grown into a more serious disease,” said Ramesh Sagili, an OSU professor and project director.

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Beekeeper George Hansen of Colton, Ore., who operates Foothills Honey Co., said European foulbrood disease used to be a spring-only event associated with poor weather.

“Now it is not only more prevalent, but it lasts. A higher percentage of colonies get it and it doesn’t disappear when the weather improves. In some cases, it never goes away,” Hansen said.

Disease impacts

The disease causes persistent colony declines and even die-offs. Diseased hives aren’t strong enough to properly pollinate, and beekeepers who pollinate early-season crops such as highbush blueberries are especially affected.

“Those who work for blueberry pollination, about 30% of hives minimum are impacted with this disease, but we don’t have solid numbers at this time,” Sagili said.

“It’s an enigmatic disease. We understand the basics, but we don’t know why this disease flares up some years and then goes down,” he added.

T.J. Hafner, research coordinator for the Oregon Blueberry Commission and agronomist for AgriCare, a farm management company, said growers face production loss or increased costs from bringing in more hives.

“When they bring the hives out of almonds, the hives are really strong. When they leave the blueberries, they’ve decreased in quality,” he said.

Whatever crop hives are going to next, there might be a cascading effect with pollination quality, Hafner added.

Hansen said some Canadian beekeepers are refusing to pollinate blueberries because they don’t want heavy losses to contribute to lower honey production months later.

Study details

Researchers have done smaller studies of the disease, but there have not been large-scale investigations, Sagili said.

“We are trying to comprehensively address the problem rather than doing it piecemeal. We’re trying to figure out all the factors that might be contributing to this disease,” Sagili said.

The study will track honeybee hives as they are transported to pollinate almonds and then blueberries across Washington, Oregon, California and Mississippi.

Four beekeepers from each state are participating, and more than 1,500 colonies will be part of the research, which includes checking frames for signs of foulbrood, estimating colony populations and surveying microbiota of bees and larvae.

Researchers will monitor colonies’ nutrition, document different climate factors, and collect samples when evidence of foulbrood is present.

In the second and third years of the grant, researchers will focus on developing disease mitigation strategies for beekeepers.

Field work will start in February in California, where beekeepers from around the country bring their hives to pollinate almonds as one of the first crops of the year.

The research team will include 10 scientists — six from OSU, two from WSU, one from UC-Davis and one from MSU, Sagili said.

European foulbrood disease is just one problem facing honeybees. Beekeepers saw overall colony loss rates of about 50% due to various factors from April 2022 to April 2023, according to the USDA.

Overall colony numbers were down only 6.8% in that time frame, however, because beekeepers replaced most of their lost colonies.