If the backyard isn’t buzzing this summer, blame it on deadly mites and the diseases they carry, says Dewey Caron, the University of Delaware’s resident ‘bee guy,’ who braves apiaries from America to the Amazon, and most recently joined a team investigating major honeybee losses in the northeastern United States.
Golden honeybees are essential for pollinating wild plants, as well as up to 90 percent of all U.S. crops, says Caron, a professor of entomology at UD and chairperson of the Eastern Apicultural Society. Unfortunately, pests such as the tracheal mite and the varroa mite are wiping out entire bee colonies, according to Caron and his colleagues.
Beekeepers report die-offs ranging from 40 percent in Delaware and 53 percent in Pennsylvania to 80 percent in Maine, says Camazine, an assistant professor of entomology at Penn State. Both tracheal mites and varroa mites feed on bee blood, he explains. Tracheal mites infect the breathing tubes of bees, while varroa mites-resembling light brown poppy seeds-camp on their victims’ backs, often bringing diseases with them.
In the wild, “only 10 percent of all feral honeybee colonies remain within the northeastern United States,” says Caron, who works in UD’s 50-year-old apiary or bee farm, “so much biodiversity has been lost.”
With a Fund for Rural America grant, awarded by the U.S. Department of Agriculture (USDA) and directed by Penn State, Caron will join beekeepers and researchers with the USDA’s Beltsville, Md., beekeeping lab, as well as state departments of agriculture from Pennsylvania, Delaware, Maryland and New Jersey to develop new strategies for fighting mites. Those efforts and other bee-related topics-from killer bees to honey prices-will be discussed July 13-17during an EAS conference near Somerset, Pa.
For fruit and vegetable farmers, bees are “the only manageable pollinator,”capable of doubling crop yields, says Caron, winner of a UD excellence-in-teaching award. They also benefit many native plant species. “All the beautiful crocuses in the spring, goldenrod in the summer and yellow flowers in the fall depend on the bee for pollination,” Caron notes.
Beekeepers can kill varroa mites by using a chemical miticide, Apistan, within affected colonies. But some don’t want to use chemicals, either for environmental or economic reasons, Caron reports. And, mites inevitably develop resistance to chemicals, prompting beekeepers to boost the dosage. Too much miticide can kill the bees as well as the mites, since both are arthropods.Young bees are particularly vulnerable to the miticide. Clearly, Caron says,”it’s no good if your patient dies on the operating table.”
In search of a longer-term solution, Camazine uses high-powered microscopes and other laboratory instruments to learn exactly how mites and their viruses affect bees. Strategies for addressing these problems may include breeding hardier bees and improved mite treatments, he says. At the USDA, for instance, scientists are investigating a long-lasting gel containing formic acid-a natural component of honey. Formic acid, legalized for mite treatment in Canada, does kill mites, but it evaporates quickly and, therefore, must be reapplied frequently. A formic acid gel may provide beekeepers with an important new alternative to Apistan, as it slows the rate of release of the chemical. Meanwhile, Camazine says his group is studying essential oils, such as eucalyptus, as possible natural mite repellents in the northeastern region.
“We need research to solve the mystery of exactly why these mite-infested bees are dying,” Camazine says. “Do the mites directly damage worker bees? Do they spread viral infection or weaken the bees’ immune system, allowing other diseases to kill the colony? Do mite-infected bees have lower cold tolerance?This knowledge could help us to develop new control strategies or to identify desirable traits to select for in breeding programs. Other studies should be conducted to evaluate whether specific lines of honey bee stock are resistant to mites.”