Researchers at Central State University in Wilberforce, Ohio, are looking for a way to kill Varroa destructor — the mite that destroys honey-bee colonies — without harming the bees, by breeding bees that fight back. Honey bees pollinate roughly a third of the nation's crops, from strawberries and oranges to the alfalfa that feeds dairy cows.

The mite, native to Asia and first found in the United States in the 1980s, is found almost everywhere honey bees live. "They're small, about the size of a pinhead. But relative to the size of a honey bee, it's a huge parasite. It's like us having a parasitic squirrel," said Reed Johnson, professor of entomology at Ohio State University. Families of mites feed on developing bees, shortening their lives, and carry deadly viruses.

Beekeepers have relied on miticides, an imperfect answer — "it can have negative effects on the queen and on the development of the larvae," Johnson said, "but in almost any case the disease is worse than the cure" — and the mite has evolved resistance, a "pesticide treadmill". "The ones that worked really well have been used up and the mites are resistant," he said. The parasite has also adapted to the American climate: "We used to see a lot of winter losses. Now we're seeing even more summer losses due to the mite resistance," said Hongmei Li-Byarlay, professor of entomology at Central State and a honey-bee specialist.

Some colonies resist infestation, and Li-Byarlay is finding out why. "We've collected mites dropped from honey-bee colonies and examined each mite under a microscope to see when there is a high percentage of these mites that are chewed off or bitten by the worker bees," she said. From a database of those counts she is developing genetic stocks, selecting the colonies with the highest share of chewed and bitten mites to replicate the traits behind their resistance.

The work has grown more important since the USDA announced earlier this year that it would close a Maryland honey-bee laboratory that studied mites. In the meantime Li-Byarlay's advice to beekeepers is to rotate treatments: "If you only use one miticide year by year, that accelerates the development of miticide resistance."

Source: Farm and Dairy