Tuesday, April 20, 2010

Honey Bee Parasitic Mites

Since the mid-1980s parasitic mites have been the number one killer of honey bees in North America. Even now in the fourth year of the large-scale die-off being called Colony Collapse Disorder it is suspected that many of the bee health problems are associated with viruses vectored by parasitic mites. Mites kill honey bees in two ways. They suck the bees’ blood and weaken the insects resulting in shorter lives for the bees. They also pass viruses to the honey bees when they puncture the bees’ exoskeleton. While parasitic mites have devastated honey bee populations in recent years, there is some promising news. Selective breeding is producing bees that can live in the presence of of mites. The first mite detected in North America, the tracheal mite, a microscopic parasite of the bees’ breathing tubes, is not the total killer of bees that it was when first detected in 1984. Selection of resistant honey bee stock and Integrated Pest Management techniques, like applying vegetable oil and sugar patties to the hive have greatly lessened hive losses from tracheal mites.

Varroa mites, visible to the eye, are parasites that breed and raise their offspring inside the honey bees’ brood cells. Fortunately, their populations grow at a relatively slow rate. It is possible to control their numbers by employing resistant honey bee stock and Integrated Pest Management techniques. The greatest defense against overwhelming populations of Varroa mites is a heritable genetic trait called hygienic behavior. Honey bees with this trait detect Varroa mites breeding in the capped brood cells and remove the affected pupa along with the mites. Monitoring of Varroa levels in the hives allows beekeepers to control the mites. Since chemical treatments cannot be used while the bees are making honey, non-chemical IPM measures are employed. Click on the picture to see a Varroa mite on a honey bee pupa that has been removed from its cell. Workers return the nutrients from the pupa to the colony.

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