A Sustainable Approach to Controlling Varroa Mites of Honey Bees

A Sustainable Approach to Controlling Varroa Mites of Honey Bees

Summary

Objectives of this project include:

1) Continue the breeding program for honeybees that display hygienic behavior;

2) Screen hygienic line of bees for other mechanisms of resistance to Varroa mites;

3) Test strategy of combining mite resistant bees (hygienic line) with alternative treatment to limit use of conventional pesticides; and

4) Conduct survey on performance of hygienic colonies in commercial apiaries.

The introduced parasitic mite, Varroa jacobsoni Oud, is the most destructive pest of honey bees today. The goal of this research is to breed for mite resistant honey bee stock and transfer the breeding technology to queen producers in the U.S. so they can breed for resistance to Varroa mites from among their own lines of honey bees. It is important to encourage beekeepers to limit the use of conventional pesticides within their bee colonies, but it is critical to provide economically viable alternatives. The experiments outlined in this proposal rely on continued collaboration and feedback from beekeepers in the North Central region. The most sustainable approach is to have beekeepers be responsible for the health of their bee colonies through environmentally sound practices.

Hygienic behavior is a mechanism of resistance to the mites. A hygienic line of honeybees is being maintained in a breeding program at the University of Minnesota. In Objective 1, the number and genetic diversity of sublines within the hygienic line will continue to be augmented to avoid inbreeding.

With current SARE support, large scale field studies were conducted in collaboration with commercial beekeepers determined that the hygienic colonies from the University breeding program demonstrated partial mite resistance in the field. It is now important to investigate additional mechanisms of resistance to
Varroa. There is evidence that some bees have the ability to suppress mite reproduction. However, mite fertility may be influenced by colony nutrition, specifically low pollen (protein) availability. Experiments are proposed in Objective 2 to address two questions: 1) Do resources affect mite fertility? and 2) Do the mites inside sealed brood cells that are not removed by hygienic colonies have reduced fertility? One experiment will compare mite fertility in colonies with ample resources with colonies that are deprived resources. The other experiment will compare mite fertility in colonies bred for hygienic behavior with unselected colonies. If it is determined that the suppression of mite reproduction is not influenced by environmental factors the trait will be included in the breeding program for mite resistance.

The hygienic line of bees still requires yearly in-hive treatments with conventional pesticides. An integrated, sustainable strategy would be to treat the hygienic line annually with an alternative compound, such as formic acid. Tests with this compound have had 60-80% efficacy, but may provide sufficient control so that partially resistant colonies can survive without conventional pesticides. In collaboration with beekeepers that winter their bees in Minnesota (non-migratory beekeepers) and with a commercial beekeeper that moves his bees south for the winter (migratory beekeeper), we will compare survivorship, mite loads and honey production between hygienic and unselected colonies that have been treated with alternative treatments or a combination of alternative and conventional pesticides.

The ultimate goal of the breeding program is to encourage beekeepers and queen breeders to propagate and sell their own hygienic lines of bees. We will conduct a limited stock release of hygienic breeder queens to beekeepers in the North Central region whose state associations have donated money toward this research. The stock release will allow beekeepers to assess the line in their own apiaries.

In Objective 4, we proposed to conduct a follow-up survey to obtain feedback and ensure interaction between the University of Minnesota and beekeepers. This portion of the proposal falls under education and outreach with the goal of promoting the well being of honeybees and the economic viability of beekeeping
operations.

Collaborators: