July 6, 1998 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 startling 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 and applied ecology at UD and chairperson of the Eastern Apicultural Society (EAS). Unfortunately, pests such as the tracheal mite and the varroa mite are wiping out entire bee colonies, according to Caron and his colleagues, Maryann Frazier and Scott Camazine of Pennsylvania State University.
During the winter of 1995-96, beekeepers reported 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 poppyseeds-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 13-17 during 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 1998 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."
Going for the Gold
Beekeepers rely on honey sales, which generated $125 million for a harvest of 209 million pounds in 1995, says Frazier, a senior entomology extension agent at Penn State. And, U.S. farmers routinely use bees to promote the growth of apples, blueberries, watermelons, cucumbers, pumpkins, squash, peas, lima beans and many other crops. Nationwide, Frazier says, the value of honeybee pollination has been estimated at $10 billion each year. As bees fly from one flower to another, collecting pollen, they carry the sticky yellow dust from male to female plants, Caron explains.
Despite their many talents, however, "bees can't be trained to perform new tricks," he points out. Instead, he says, beekeepers have routinely imported different varieties of honeybees whenever they needed a species offering a particular characteristic. Honeybees originally were brought to the United States from Europe 400 years ago, he says, and now some 120,000 beekeepers maintain 3 million colonies across the country. When U.S. bees succumbed to bacteria in the mid-1880s, beekeepers imported a hardier Italian species.
Well-meaning South American bee breeders also brought the Africanized or "killer" bee to Brazil, Caron says. And, the varroa mite may have hitched a ride from Japan to South America, then hopped on the backs of bees headed for the United States, appearing in the United States in 1987.
"Our bees had little natural resistance to this imported mite," he says, "and losses started showing up immediately, particularly over the winters, when bees are clustered together with their honey."
Killer Bees Chill Out
When he isn't worrying about mites, Caron has been known to visit Bolivia in search of killer bees. Notorious in tropical climates for their aggressive behavior, killer bees have so far spread from South America to Texas and the southwestern United States. What would happen, Caron wondered, if killer bees made their way as far north as Delaware?
After a 12-hour airplane ride, Caron's journey began at the headwaters of Bolivia's Amazonian rivers. There, he deliberately antagonized killer bees by rattling a metal ball in front of them. Then he counted the number of sting marks on his gloved arm. In such lowland tropics, he says, "All the bad things you've heard about killer bees are true."
Caron then traveled to cooler regions of Bolivia. At 12,000 feet above sea level, in the capital city of La Paz, cooler weather seems to help killer bees chill out, he reports. Bee wax melts at 144 degrees Fahrenheit, Caron says, and bees in tropical regions may perceive any disturbance as potentially life-threatening.
Surprisingly, the varroa mite lives on killer bees, too, but "doesn't seem to cause any problems in tropical regions," Caron says. He's quick to caution, however, that intentionally importing killer bees to Delaware or any other cool-weather regions would be "an extremely bad idea."
Despite deadly mites, killer bees and an 18 percent drop in honey sales over the past 15 years, a dwindling but dedicated population of U.S. beekeepers have continued to "go for the gold," Caron says. His research has shown that the price tag on a jar of honey can vary dramatically along the same stretch of road, but it's still a bargain. Priced at 0.19 cents per pound in 1937, U.S. honey now averages about $2.00 per pound, he reports.
"Honey isn't essential for the human diet," Caron says, "but most of us love that sweet taste. And, honeybees are a critical species for pollinating food and decorative plants. We need to do what we can to make sure they continue to thrive."
CARON'S WEB PAGE: http://copland.udel.edu/~dmcaron/
MITE PHOTOS: http://www.psu.edu/dept/beehive/photgal.html
BEE CONFERENCE: http://apicultureNE.cas.psu.edu/EASmeetSched.html
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