Entomologist John Harbo prepares a queen bee for artificial insemination. Click the image for more information about it.

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Trait in Honey Bees Keeps Mites From Multiplying

For more than 20 years, beekeepers have been battling varroa mites. The tiny, bloodsucking parasites weaken adult bees and sometimes cause deformities. But entomologists with the Agricultural Research Service have discovered that some bees have a built-in defense against varroa mites, a trait that can be bred into any bee population.

Honey bees deliver pollen necessary for the production of $15 billion worth of U.S. crops. Varroa mites are a serious threat to this important, bee-dependant productivity and can wipe out an untreated colony in under two years.

Called SMR, for "suppressed mite reproduction," the newly-found trait protects bees by keeping harmful varroa mites from reproducing. It's hoped that when adequately bred into bee populations, SMR can one day free beekeepers from their dependance on chemical miticides.

ARS entomologists John R. Harbo and Jeffrey W. Harris, in the agency's Honey Bee Breeding, Genetics and Physiology Research Unit at Baton Rouge, La., discovered the SMR trait while searching for the reason behind reduced mite populations observed in some bee colonies. While honey bees can fend off mites through grooming and other hygienic behaviors, a different factor appeared to be at play in those colonies.

The researchers found that some mites simply weren't reproducing. They watched female mites entering brood cells--the small pockets, or honeycomb, where young bees develop--but not laying any eggs. Following genetic studies, the researchers determined that a trait in these honey bees was responsible for inhibiting the mites' reproduction.

To help beekeepers whose hives are suffering from varroa infestations, ARS has provided the SMR trait to Glenn Apiaries, a commercial queen honey bee producer in Fallbrook, Calif., that sells SMR breeder queens. With selective breeding, the SMR trait can eliminate mite reproduction in worker brood cells.

Harbo and Harris are studying a second trait in bees linked to mite resistance. Called P-MIB, for "percentage of mites in brood," the trait is an ideal complement to SMR because it curbs mite populations from outside, rather than inside, the brood cell where SMR comes into play.

Read more about this research in the May issue of Agricultural Research magazine.

ARS is the U.S. Department of Agriculture's chief scientific research agency.