Mite takes major bite out of honeybee population, threatens crops

ITHACA — A tiny mite is causing major problems for New York’s honeybee population and is threatening the fruit and vegetable crops that are a major part of the state’s $500 million agriculture industry.

The varroa mite is a common parasite that weakens honeybee colonies by feeding on bee blood and fat stores, and transmitting deadly viruses across the colony. One of those viruses, deformed wing virus, causes misshapen wing growth in infected bees.

With crops like apples, squash, tomatoes, strawberries and cherries dependent on bee pollinators, a rise in sick populations puts at risk $500 million in annual New York agricultural production.

Cornell University scientists are tackling the problem by working with beekeepers whose colonies are at risk. Launched in 2016, the New York State Beekeeper Tech Team sampled 309 honeybee colonies from 70 apiaries across New York last fall. They found that 90 percent of the colonies were infested with varroa mites, and discovered deformed wing virus in 96 percent of the colonies and 100 percent of the operations sampled.

“When colonies have high levels of deformed wing virus, the affected bees are unable to fly and die at a young age,” said Emma Mullen, honeybee extension associate and senior lead of the beekeeper team. “It can be quite detrimental – varroa mites and their associated viruses are a leading cause of death for honeybee colonies.”

Even more alarming, according to Mullen, is that 78 percent of operations had varroa mite levels that exceeded the economic threshold of 3 mites per 100 bees, an important predicator that the colony will die within one to two years or experience reduced honey production. Surpassing that threshold demonstrates that the mites are not being managed effectively and are posing a critical risk to colony health, Mullen said.

Mullen and Scott McArt, assistant professor in the Department of Entomology in the College of Agriculture and Life Sciences, have been collaborating with beekeepers throughout the state to find ways to keep their bee colonies healthy.

When it comes to varroa mites, this collaboration is more necessary than ever. The Cornell team found that, despite rising infestations, only 36 percent of beekeepers were monitoring mites in 2016. The high mite levels suggest that the current management approaches New York beekeepers are using may not be effective.

The beekeeper team assists beekeepers by surveying their colonies for parasites, pathogens and pesticides, and analyzing the beekeepers’ management practices. The team works with the beekeepers to develop an integrated pest management plan that will reduce colony losses through monitoring and a variety of potential treatments.

“We are committed to helping beekeepers maintain their business and help our farmers in the process,” McArt said. “We can see if there is year-to-year variation or if there are consistently certain types of management practices that are much better for beekeepers than others.”

COMMENTS