Varroa Resistant and Hygienic Bees


Natural Selection and the Benefit of the Intrance

There is consensus that the ecto-parasitic mite Varroa destructor, which is now found almost everywhere in the world, is the main biological threat to global apiculture. It has also almost completely wiped out the wild European honey bee, Apis mellifera, populations. The perceived solution to dealing with Varroa is to treat with a variety of products, often at different times of the year with scant regard to the actual population dynamics in the hive. The issue for apiculture therefore are the frequent control measures against the mite throughout the season, which if carried out without understanding blocks possible genetic adaptation. Allied to this are poor beekeeping practices that do not allow for the natural evolutionary aspects of colony fission to occur. Queens are frequently replaced in the quest for higher honey yields, bees are kept in areas where the environment plays a larger role in colony health than it should (monoculture, spraying, poorly managed colonies), beekeepers do not know how to observe and develop hygienic behaviour and are also too scared to lose colonies in the process of improving their stock.

I have found it extremely difficult to "breed" Varroa resistant bees within our local environment, but I have found certain strains to have a higher tolerance and definitely engage in greater "hygienic"  behaviours. The chewing of cell cappings and removal of affected brood is now much more common in the apiary than ever before and certain colonies are now treatment free. However, it must be remembered that even with best practice, the colony load in an area as well as poor apicultural practices will always lead to a re-establishment or increase of varroa levels.

Based on these data, I try to allow the colonies to naturally select for resistance to varroa by stopping treatment of the varroa mite in managed colonies and using a few methodological preconditions which help to avoid unacceptable outcomes. Such natural selection can be performed on a local scale by local beekeepers, with their own local bees which will contribute to local adaptation. However it does require the cooperation of local beekeepers, a knowledge of 'feral' colonies, and a methodological process to deal with the homing of swarms or cutouts.

Honey bees can thrive in nature if enough nesting sites of correct size (trees with cavities), and sufficient food (nectar and pollen) are available to support colonies during the whole year. In addition, honey bees need to be sufficiently resilient to a variety of challenges and stresses, including those imposed by the beekeeper. The use of appropriate entrances is a step in using Integrated Pest Management in a way that is more natural and helps bees control their environment more effectively.

Honey bees are an endemic wild species in (Western) Europe, nevertheless there are only very few feral populations of colonies, partly because there is a lack of nest sites. Since the presence of Varroa destructor most of the remaining feral populations have succumbed. Because beekeepers treat colonies against the mites, no selection for resistance can take place.