Beekeepers can produce and maintain colonies of domesticated honey bees that are resistant to varroa mites, one of the insects' worst enemies, according to nearly five years of tests by Agricultural Research Service scientists in Tucson, Ariz. Varroa mites are eight-legged, blood- sucking parasites that have decimated hives of the domesticated honey bee, Apis mellifera, in nearly every state.

Eric H. Erickson of the ARS Carl Hayden Bee Research Center in Tucson led the Arizona study, in which about 190,000 bees were analyzed. The scientists populated three research apiaries with survivor bees from Arizona hives not treated with mite-killing chemicals called miticides. To see if the colonies would become naturally infested, the scientists kept the hives free of the miticides. Then, the researchers determined whether the bees had been attacked by mites. Colonies of susceptible bees were removed and replaced with progeny from the mite-tolerant colonies. The test hives averaged only 7 mites per 100 bees at the end of about four years of this selective breeding. In some years, some hives were mite free.

The ARS experiment, reported in the December 1999 issue of the American Bee Journal, provides more evidence that beekeepers and breeders can keep hives relatively free of mites through selective breeding to populate apiaries with mite-tolerant stock. The scientists recommend that beekeepers regularly inspect their colonies for mite resistance and then select queens--for breeding--from the colonies with the lowest mite populations. Some beekeepers and breeders are already doing this. And scientists in Germany and Russia, for instance, have also found Apis mellifera hives that are naturally resistant to the mites.

Erickson did the work with Anita H. Atmowidjojo of the University of Arizona and commercial beekeeper Lenard H. Hines of Sierra Vista, Ariz. According to Erickson, it is relatively easy to find varroa-tolerant colonies in commercial hives and to produce and maintain varroa-tolerant honey bees.

Currently, miticides are the principal control. The new findings offer beekeepers another new option for strengthening their hives' mite resistance. What's more, ARS announced in August that mite-tolerant queens, descended from honey bees the agency imported from Russia, would be commercially available next year. ARS scientists in Baton Rouge, La., led by Thomas E. Rinderer, imported and tested the mite-tolerant Russian honey bees.

The Agricultural Research Service is USDA's chief research agency.