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 increase—and many
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Contact: Janet Raloff
jar@sciserv.org
202-872-5117
Science News
6-Aug-1998