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.
