Saturday, November 27, 2010

Live or Let Die?

After two weeks in place in the bee hives, the thymol treatments have evaporated from their gelled state. The thymol vapors have killed a large proportion of the colony’s parasitic mites.   The mites fell from the bees and can be seen on the plastic inserts that covered the screened bottom boards and concentrated the thymol fumes. My 10-year-old grandson, Ethan, removes the inserts and hive spacer shims used to administer the thymol. Thymol is a product of the thyme plant, a common herb used to make pizza sauce. It is considered less dangerous to the honey bees than chemical miticides. The harsh miticides are known to lead to infertility in queens and drones. These agents have also led to resistant strains of parasitic mites.

In the future, it is hoped that we will not have to use any treatments at all to control mites. Great efforts are being made to breed strains of honey bees that are resistant to the deadly Varroa mites. These bees have a genetically heritable behavior trait that allows them to detect reproducing Varroa growing in the cells with developing honey bee pupae. The bees open the cells and remove the pupae along with the parasitic Varroa. This is called hygienic behavior. It is hoped that through genetic selection honey bees will evolve that can live in the presence of parasitic mites.  That seems to have occurred to a considerable degree with tracheal mites, but not yet with Varroa. In practicality, we are a long way away from pure honey bee genetic control of Varroa mites. Mite resistance is greatly diminished with each supersedure of a colony’s queen. A few beekeepers are attempting to use a “live or let die” approach to Varroa control, letting the mites select the resistant colonies. A more practical approach, however, seems to be an integrated pest management plan that employs numerous mite controls including “soft” chemicals, like thymol” as needed to rapidly knock down mite populations exceeding self-defined thresholds.

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