If the backyard isn't buzzing this summer, blame it on deadly mites and thediseases 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 UnitedStates.
Golden honeybees are essential for pollinating wild plants, as well as up to 90percent of all U.S. crops, says Caron, a professor of entomology and appliedecology at UD and chairperson of the Eastern Apicultural Society (EAS).Unfortunately, pests such as the tracheal mite and the varroa mite are wipingout entire bee colonies, according to Caron and his colleagues, Maryann Frazierand Scott Camazine of Pennsylvania State University.
During the winter of 1995-96, beekeepers reported die-offs ranging from 40percent in Delaware and 53 percent in Pennsylvania to 80 percent in Maine, saysCamazine, an assistant professor of entomology at Penn State. Both trachealmites and varroa mites feed on bee blood, he explains. Tracheal mites infect thebreathing tubes of bees, while varroa mites-resembling light brownpoppyseeds-camp on their victims' backs, often bringing diseases with them.
In the wild, "only 10 percent of all feral honeybee colonies remain within thenortheastern United States," says Caron, who works in UD's 50-year-old apiary orbee farm, "so much biodiversity has been lost."
With a Fund for Rural America grant, awarded by the U.S. Department ofAgriculture (USDA) and directed by Penn State, Caron will join beekeepers andresearchers with the USDA's Beltsville, Md., beekeeping lab, as well as statedepartments of agriculture from Pennsylvania, Delaware, Maryland and New Jerseyto develop new strategies for fighting mites. Those efforts and otherbee-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 1998 UDexcellence-in-teaching award. They also benefit many native plant species. "Allthe beautiful crocuses in the spring, goldenrod in the summer and yellow flowersin the fall depend on the bee for pollination," Caron notes.
Beekeepers can kill varroa mites by using a chemical miticide, Apistan, withinaffected colonies. But some don't want to use chemicals, either forenvironmental or economic reasons, Caron reports. And, mites inevitably developresistance to chemicals, prompting beekeepers to boost the dosage. Too muchmiticide 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 andother laboratory instruments to learn exactly how mites and their viruses affectbees. Strategies for addressing these problems may include breeding hardier beesand improved mite treatments, he says. At the USDA, for instance, scientists areinvestigating a long-lasting gel containing formic acid-a natural component ofhoney. Formic acid, legalized for mite treatment in Canada, does kill mites, butit evaporates quickly and, therefore, must be reapplied frequently. A formicacid gel may provide beekeepers with an important new alternative to Apistan, asit slows the rate of release of the chemical. Meanwhile, Camazine says his groupis studying essential oils, such as eucalyptus, as possible natural miterepellents in the northeastern region.
"We need research to solve the mystery of exactly why these mite-infested beesare dying," Camazine says. "Do the mites directly damage worker bees? Do theyspread viral infection or weaken the bees' immune system, allowing otherdiseases to kill the colony? Do mite-infected bees have lower cold tolerance?This knowledge could help us to develop new control strategies or to identifydesirable traits to select for in breeding programs. Other studies should beconducted to evaluate whether specific lines of honey bee stock are resistant tomites."
Going for the Gold
Beekeepers rely on honey sales, which generated $125 million for a harvest of209 million pounds in 1995, says Frazier, a senior entomology extension agent atPenn State. And, U.S. farmers routinely use bees to promote the growth ofapples, blueberries, watermelons, cucumbers, pumpkins, squash, peas, lima beansand many other crops. Nationwide, Frazier says, the value of honeybeepollination has been estimated at $10 billion each year. As bees fly from oneflower to another, collecting pollen, they carry the sticky yellow dust frommale to female plants, Caron explains.
Despite their many talents, however, "bees can't be trained to perform newtricks," he points out. Instead, he says, beekeepers have routinely importeddifferent varieties of honeybees whenever they needed a species offering aparticular characteristic. Honeybees originally were brought to the UnitedStates from Europe 400 years ago, he says, and now some 120,000 beekeepersmaintain 3 million colonies across the country. When U.S. bees succumbed tobacteria 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 ridefrom Japan to South America, then hopped on the backs of bees headed for theUnited States, appearing in the United States in 1987.
"Our bees had little natural resistance to this imported mite," he says, "andlosses started showing up immediately, particularly over the winters, when beesare clustered together with their honey."
Killer Bees Chill Out
When he isn't worrying about mites, Caron has been known to visit Bolivia insearch of killer bees. Notorious in tropical climates for their aggressivebehavior, killer bees have so far spread from South America to Texas and thesouthwestern United States. What would happen, Caron wondered, if killer beesmade their way as far north as Delaware?
After a 12-hour airplane ride, Caron's journey began at the headwaters ofBolivia's Amazonian rivers. There, he deliberately antagonized killer bees byrattling a metal ball in front of them. Then he counted the number of stingmarks on his gloved arm. In such lowland tropics, he says, "All the bad thingsyou've heard about killer bees are true."
Caron then traveled to cooler regions of Bolivia. At 12,000 feet above sealevel, in the capital city of La Paz, cooler weather seems to help killer beeschill out, he reports. Bee wax melts at 144 degrees Fahrenheit, Caron says, andbees in tropical regions may perceive any disturbance as potentiallylife-threatening.
Surprisingly, the varroa mite lives on killer bees, too, but "doesn't seem tocause any problems in tropical regions," Caron says. He's quick to caution,however, that intentionally importing killer bees to Delaware or any othercool-weather regions would be "an extremely bad idea."
Despite deadly mites, killer bees and an 18 percent drop in honey sales over thepast 15 years, a dwindling but dedicated population of U.S. beekeepers havecontinued to "go for the gold," Caron says. His research has shown that theprice tag on a jar of honey can vary dramatically along the same stretch ofroad, 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 lovethat sweet taste. And, honeybees are a critical species for pollinating food anddecorative plants. We need to do what we can to make sure they continue tothrive."
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
Materials provided by University Of Delaware. Note: Content may be edited for style and length.
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