Tiny varroa mite is a serious threat to honeybees

Jul 3, 2017

Credit freeimages.com/Brandon Keim

A tiny mite is believed to be responsible for the loss of 44 percent of New York's honeybee colonies in the last year, according to scientists at Cornell University.

"That's pretty dramatic,” said Emma Mullen, an associate at Cornell University’s honeybee extension and leader of the New York State Beekeeper Tech Team. “If you think about the dairy industry or some other agricultural industry losing 44 percent of their cows one year? It's a lot to bounce back from." That's compared to about a 33 percent honeybee colony loss nationally.

The varroa mite has been found throughout North American and in some parts of Europe. It is a common parasite that weakens and sometimes wipes out honeybee colonies by feasting on the bees' blood and fat stores.

"The worst thing that they so is transmit several different viruses to honeybees,” Mullen said. “It's similar to how mosquitoes might transmit viruses to humans. It's actually this combination of the viruses and the mite that causes the colony to die much quicker than if it was infected with the mite alone."

Scientists at Cornell and other research institutions are trying to find out why this minuscule mite, which has been around since the 1980s, has become so much more of a threat to honeybees in the last few years.

The Beekeeper Tech Team is working directly with local beekeepers to try to mitigate the damage.  Mullen said they're trying new chemical treatments to eliminate the mites and encouraging beekeepers to use different genetic stocks of bees which may be more resistant to the mite.

A dramatic reduction the honeybee population will impact agriculture in New York. It's just not clear to what extent.  Bees are needed to pollinate apples and other crops such as beans and pumpkins. Growers rent bee colonies to pollinate these crops when they’re flowering.

"We haven't directly evaluated the economic impacts of the varroa mite on our crop yields and crop production but you can see that there definitely is a possibility that continuously losing honeybee colonies can impact our agriculture," Mullen said. She says crops that depend on bee pollination represent $500 million dollars in annual agricultural production statewide.

One of the viruses spread by the varroa mite causes misshapen wing growth in the infected bees.  When colonies have high levels of deformed wing virus, the affected bees are unable to fly and die at a young age.

The Beekeeper Tech Team found that last fall, 90 percent of the 309 honeybee colonies it tested last fall were infested with varroa mites.  

The varroa mite is believed to be one of the factors linked to Colony Collapse  Disorder, a phenomenon that appeared in the U.S. and Europe between 2006 and 2010.