That goal moved a step closer last week. The first generation of bees produced by 90 expatriate queens, just released from quarantine, has significantly outperformed U.S. members of their species, Apis mellifera, in resisting infestation by varroa mites.
This parasite, which first turned up among U.S. honeybees 11 years ago, has taken a devastating toll. Feeding off their hosts' blood, the energy-sapping mites weaken and soon kill the bees (SN: 2/8/97, p. 92). Moreover, mites in four states have developed resistance to the one pesticide approved for use against them, notes Thomas E. Rinderer of the U.S. Department of Agriculture honeybee laboratory in Baton Rouge, La.
Such pesticide-resistance leaves beekeepers defenseless, he says. Indeed, he notes, because wild honeybees never received treatment, "they're gone." Though swarms that stray from beekeepers' colonies may survive a few months in the wild, he says, these days "they're doomed, too."
The parasites develop on bee pupae. Once a bee emerges as an adult, it normally lives 30 days or more, depending upon how hard it works. But an infested worker may survive only 3 to 5 days in its sickly state. The mites, which also attack adults, reproduce on a 10-day cycle, allowing them to quickly kill off a colony.
In the new tests, Rinderer's team exposed 90 parasitefree colonies to mites. Each colony contained a Russian-hatched queen and up to 60,000 of her offspring. About 12 weeks later, the USDA scientists tallied how many mites infested the adults and pupae.
From previous data on U.S. colonies, "we would have expected an 11.4-fold increase in mites during the test period," Rinderer says. Instead "we got an average 3.9-fold increaseand many colonies had no increase. This is extremely exciting."
Though many honeybee populations along the Primorski region of Russia's Pacific coast have had a century to develop natural resistance to the varroa mite, bees who arrived there more recently show little ability to coexist with the parasite. The current tests were designed to identify and eliminate these weaker bees from any U.S. breeding program.
Imported a year ago, the queens, which can live up to 3 years, are becoming quite elderly. Colonies headed by their daughters, however, are now beginning a new wave of tests to compare them directly with U.S. hives. The queens, which mate only once, carry sperm from descendants of Primorski-hatched bees. By next spring, Rinderer's team plans to begin distributing mated Russian queens to beekeepers for experiments to evaluate how well they pollinate plants and produce honey under field conditions.
The Russian queens are fueling considerable excitement among apiarists, says Troy Fore of the American Beekeeping Federation in Jesup, Ga. The cost of treating colonies with the varroa miticide can eat up 20 percent of a beekeeper's gross earningsor about 80 percent of the intended profit, he says. Bees with Russian genes should reduce the need for some or all of these expensive treatments, he adds.
The Russian queens also "offer to throw the [mite] resistance gene into [stray] bees," reestablishing a self-sustaining feral community, notes beekeeper Kim Flottum, who edits Bee Culture in Medina, Ohio.
Cowen, R. 1991. Fighting the mite: May the best bee win. Science News 139(Jan. 5):5.
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Mlot, C. 1997. Bees and keepers tackle mite-y problem. Science News 151(Feb. 8):92.
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Raloff, J. 1996. Growers bee-moan shortage of pollinators. Science News 149(June 29):406.
623 West Liberty Street
Medina, OH 44256
American Beekeeping Federation
P.O. Box 998
Jesup, GA 31598
Thomas E. Rinderer
United States Department of Agriculture
Honey-Bee Breeding, Genetics & Physiology Laboratory
1157 Ben Hur Road
Baton Rouge, LA 70820
From Science News, Vol. 154, No. 6, August 8, 1998, p. 84.
Copyright Ó 1998 by Science Service.