Parasite-free honeybees enable study of bee health

Honeybee colonies in Newfoundland free of invasive parasites may help with study of colony losses; Oregon State reports challenging trend.

An international team of researchers has discovered honeybee colonies in Newfoundland that are free of the invasive parasites that affect honeybees elsewhere in the world. The populations offer a unique opportunity to investigate honeybee health, both with and without interfering interactions from parasites.

"Invasive parasites — such as Nosema ceranae, a fungus, and Varroa destructor, a mite — have incurred heavy economic penalties on the honeybee industry via colony losses and reduced productivity of surviving colonies, and both parasites threaten global food security because of reduced pollination services to agriculture," said Nancy Ostiguy, associate professor of entomology at Pennsylvania State University. "The extent to which these detriments are attributable to specific parasite species is difficult to assess, however, because of the occurrence of multiple parasites within honeybees. Studying the effects of these parasites is even more challenging because few areas in the world have western honeybee colonies that are free of invasive parasites."

Ostiguy and her colleagues found a geographical area in Newfoundland in which a number of important invasive honeybee parasites, including varroa mites and N. ceranae, do not exist. The researchers used molecular techniques to test for the presence of viruses and N. ceranae in honeybee colonies managed by beekeepers. They used a visual screening method to search for insect parasites, including Varroa destructor. They then assessed the colonies for visual signs of illness and related the illness data with the presence or absence of parasites or viruses.

In the Newfoundland colonies, the researchers found the parasite N. apis, the species that has been displaced by N. ceranae elsewhere, and the pathogens black queen cell virus and deformed wing virus.

"Despite the presence of these parasites and pathogens, colony losses in Newfoundland are very low — similar to the mortality rates reported in the U.S. before the introduction of Varroa destructor," Ostiguy said.

The results appear in a recent issue of PLOS ONE.

According to Ostiguy, the team will continue to investigate the relationships between various pathogens and parasites of honeybees, along with various stressors, such as pesticide exposure, with the goal of providing information to help keep honeybees healthy.

"Our ability to find European honeybee populations free of invasive parasites is shrinking," she said. "These parasite-free populations in Newfoundland are essential for our ability to understand the interactions among various parasites and pathogens of honeybees."

Meanwhile, more than one in five commercial honeybee hives in Oregon did not survive last winter, continuing a financially challenging trend for professional beekeepers.

Between Oct. 1 and March 31, Oregon beekeepers reported a 21.1% loss in colonies of the crucial crop pollinators, according to a survey by Oregon State University. The latest figures are a slight improvement over the state's average annual loss of 22% over the past six years.

Nationally, commercial beekeepers reported a 23.2% decline last winter, according to a survey by the Bee Informed Partnership, a countrywide collaboration among research labs focusing on honeybee declines, an announcement from Oregon State said. An average of about 30% of colonies nationwide has died each winter over the past decade.

"These are challenging times for beekeeping and we have reason to be alarmed," said Ramesh Sagili, an entomologist with Oregon State University's College of Agricultural Sciences who has been conducting honeybee colony loss surveys for the past five years. "While 10-15% loss of colonies is considered acceptable, current rates of decline could drive professional beekeepers out of business."

To replace lost colonies, beekeepers must split healthy hives of 50,000 bees or more — a process that takes months and adds substantial costs for labor, new queens and equipment. However, as these lost colonies are replaced, there is not a drop in the total number of hives each year, according to Sagili.

The U.S. is home to 2.6 million managed honeybee colonies, according to the Bee Informed Partnership.

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