Researchers believe that they have pinpointed the cause of a history-making recent honey bee die-off, and what they found casts a gloomy outlook for the important insects.
Per a study released last month by the U.S. Department of Agriculture, mites, viruses and insecticide resistance all played a role in the loss of 62% of commercial honey bees in the U.S. from last June through this January. Until a new insecticide or something to attack the viruses is created, honey bees are still at risk.
Parasitic Varroa mites are a known stressor on honeybees, and they are also known to be a vector for viruses, the researchers explained.
“While localized honey bee colony losses have been documented throughout the history of beekeeping, they have been especially frequent following the arrival in a region of the invasive honey bee ectoparasitic mite Varroa destructor. This nearly ubiquitous mite vectors some, but not all, honey bee viruses, and has been a major synergist for Deformed wing virus,” said the study authors.
To mitigate the impact of the mites, insecticides have been used. According to the study, beekeepers have been reliant on a miticide called amitraz since mites developed resistance to other miticides called coumaphous and tau-fluvalinate. Amitraz was first developed in 1969 by the Boots Co. in England.
Now it looks like amitraz is succumbing to the same fate as the other miticides, study authors found.
“In analyzing mites from collapsed colonies, all screened mites showed a genetic marker associated with amitraz resistance,” it said. “All beekeepers in our screening relied upon amitraz for the majority of their miticide applications, underscoring the challenges faced by beekeepers in controlling mite damage.”
It’s not surprising that most beekeepers relied on amitraz. According to the American Association for the Advancement of Science, it is the only viable miticide of its kind left.
“Unfortunately, effective new compounds are notoriously difficult to develop, and amitraz represented one of the best remaining treatments,” said the association.
Authors of the recent study noted that honey bees are an integral part of agriculture both in the U.S. and around the globe, as they pollinate many crops. In the U.S., they provide up to $30 billion worth of services, pollinating more than 90 commercial crops, and up to $387 billion worldwide.
Once honey bees become infected with a virus, they tend to live shorter lives. When bees start dying faster than the rate of replacement through brood rearing, their colonies are at risk of collapsing. Those colonies crashing from viral infections then pose a risk for neighboring colonies.
“There is a lot at stake,” said Danielle Downey, executive director of Project Apis m., the nonprofit that conducted a survey related to the recent bee die-off. Aaron Gross, a toxicologist at Virginia Polytechnic Institute and State University, said the study findings are “concerning.”
With the possibility that the only miticide available might be off the table, some researchers are hoping to develop methods that would attack the actual viruses that infect honey bees. However, that work could take years, according to the AAAS. For now, experts recommend cycling through other insecticides, frequently sterilizing equipment with alcohol or fire, and isolating sick colonies to prevent viral spread.