Minnesota honeybees’ behavior could help decrease mite problems

Hygienic honeybees clean colonies of a parasite, the Varroa destructor mite.

Jerret Raffety

Researchers within the University’s department of entomology are breeding honeybees with a special Minnesota secret that could save many future colonies.

By studying honeybees with a gene to keep their surroundings clean, the scientists said, they are hoping to slow a deadly mite population that plagues honeybee colonies in the United States.

For more than 10 years, the scientists have been breeding honeybees that exhibit hygienic behaviors, calling the breed the Minnesota hygienic line. One of their behaviors is cleaning the colonies of a blood-sucking parasite, Varroa destructor mites.

Experts said they believe the mites are responsible for killing approximately half of all honeybee colonies last year.

Marla Spivak, an entomology department professor, is leading the honeybee project with the special hygienic touch that helps honeybees stay alive.

“The Varroa destructor mite feeds on the blood of honeybees, which weakens the bees and shortens their lifespan,” Spivak said.

She said all U.S. honeybee colonies have the mites.

Since 1993, Spivak said, the department has distributed hundreds of queen honeybees to beekeepers nationwide.

The queen honeybees change the behavior of a colony by laying eggs that will create the next generation of worker honeybees that will have hygienic conduct, Spivak said.

Once the mites are inside a colony, they feed off honeybee pupae or larvae, she said. The mites also lay eggs on the developing honeybees in the colony, she said.

The mites feed off mature honeybees until they enter a colony. Once inside, the mites will enter colony cells that have honeybee pupae, lay their own eggs and continue to feed off the developing honeybees.

Honeybees with the Minnesota hygienic behaviors detect the mites’ presence, said Eric Mussen, an official for the American Association of Professional Apiculturists.

“Wounded pupae apparently smell wounded, and hygienic bees clean them out,” he said.

But once more than 3,500 mites have entered one colony, the mites will likely destroy the honeybee population, Mussen said.

Chemical pesticides have also been used to stop the mites. But scientists have found the mites grow resistant to them during a long period of exposure, Spivak said.

“What we need is a sustainable solution for the mite problem,” she said.

Several farmers throughout the nation use honeybee colonies to exchange pollens between plants, creating seeds and fruits, she said.

John Harbo, a research entomologist for the U.S. Department of Agriculture, said that the mite, native to Southeast Asia, spread into Europe and South America in the 1970s then extended into the United States in the late 1980s.