In this project, signficant progress was made towards breeding for resistance to Varroa mites in honey bees and getting beekeepers to adopt northern-bred mite-tolerant stocks. Breeding involved selecting for a novel trait, mite-grooming behavior.
The most recent surveys in North America and Europe have shown that among risk factors looked at, Varroa mites are still the most commonly associated problem with winter kills of bee hives.
1) Increase mite-grooming traits in the Purdue honey bee breeding program.
2) Demonstrate the benefits of breeding for resistance to Varroa mites.
3) Promote the use of resistant stock by Midwest beekeepers.
4) Incorporate both VSH and grooming behavior traits in stocks.
We published a paper describing a new laboratory assay for measuring grooming behavior in groups of caged bees and showed that it correlates with the proportion of chewed mites that are falling off of bees in colonies. We showed beekeepers how they can measure the proportion of chewed mites in their own hives to perform their own selection. After selecting for high proportions of chewed mites, we made crosses for three years with artificial insemination and are currently overwintering inseminated queens. Crosses are made from queens in hives that were selected the previous year and survived a northern Indiana winter. In the fall of 2011, another laboratory assay was used in which individual mites were placed on individual bees and measurements were made for the time it took them to start grooming to remove the mite. The bees from the selected stock (daughters of the artificially inseminated queens) responded significantly faster and showed more grooming bouts than unselected stock.
Progress in adoption of resistant stock. We have partnered with Midwest beekeepers to promote the idea of learning to raise queens and select for resistance. One of our key participants, Dave Shenefield, received a grant in 2011 from the Indiana Dept. of Agriculture, which was managed by the Indiana State Beekeeping Assoc. This grant helped to educate beekeepers and distribute about 1,500 queen cells. Coordination was set up so that representatives of local beekeeping clubs could buy and distribute queen cells and some of the funds will help to sustain this outreach program into 2012. Two queen rearing workshops have been conducted each year for the past three years. In 2011, these workshops were held at the 10th annual Heartland Apiculture Society conference in Vincennes, IN, which was chaired by Greg Hunt. The program for the conference was developed along a theme, “Helping bees help themselves, breeding healthy bees”, and drew about 400 Midwestern beekeepers.
1) Six shortcourses in queen-rearing and selection methods were conducted for Midwest beekeepers and queen breeders.
2) One instrumental insemination class was conducted.
3) Approximately 4,500 queen cells or queens from selected stock were distributed to beekeepers.
4) Laboratory assays for mite-grooming behavior were developed for groups of caged bees and individual bees.
5) Selected stock showed improved mite-grooming behavior in laboratory assays.
6) Selected stock showed improved suppression of mite population growth in the field.
6) Selected stock showed improved disease resistance in the field.
We also tested the progeny of commercial queens commonly purchased in Indiana against open-mated daughter queens from one of our breeders in a side-by-side test. New colonies were initiated in comb from colonies that died the previous winter. Queens were introduced into the colonies with several thousand bees in June. On October 11th, we measured the number of mites per 100 grams of adult bees and found that the colonies with commercial queens had about 6-fold higher mite levels (see Figure 1). Ten of the 14 commercial-source colonies showed symptoms of chalkbrood (a fungal disease that kills larvae), and half of them had bees with symptoms of deformed wing virus, which is a characteristic disease associated with parasitic mite syndrome and colony collapse. None of the 14 colonies from the Purdue breeding program showed these symptoms. These colonies will be assessed again in the spring for mite levels and winter mortality and results analyzed. We intend to publish our results in both scientific and trade journals to demonstrate the importance of breeding for mite resistance, and to present results at the national meetings.
In the spring of 2012 we will make crosses between our stock and stock selected for Varroa-sensitive hygienic behavior (VSH) to incorporate the grooming behavior trait and VSH in one breeding line. Grooming reduces mites on adult bees, while VSH reduces mite levels in the brood. We have not combined these traits yet (one of the projects goals) because we wanted to be sure that we have sufficiently increased grooming behavior in our lines.
Educational & Outreach Activities
Hunt GJ, Shenefield D, Given K, Tsuruda J. 2011. An update on breeding efforts in Indiana. Bee Culture November 25-31. (also published in American Beekeeping Journal).
Andino GK, Hunt GJ. 2011. A scientific note on a new assay to measure honeybee mite-grooming behavior. Apidologie 42:481-484.
Hunt GJ, Breeding bees for resistance to parasites and diseases. 2010. Am Bee J 150(7):667-669. (also published in Bee Culture).
Rinderer TE, Harris JE, Hunt GJ, de Guzman LI. 2010. Breeding for resistance to Varroa destructor in North America. Apidologie 41:409-424.
Web-based publications on eXtension:
The economic impact of the breeding program cannot be estimated until there is a better estimate of the survivability of the selected stock compared to the various commercial queens available primarily from southeastern US and California. We have compared mite resistance to one commercial source and hope to have data on winter survival in comparison to two commercial sources in the spring of 2012.
The three beekeeper participants listed for this project include two of the largest beekeeper operations in Indiana, with about 2,500 colonies each and the third has about 500 colonies. One of the former stated that the increased hardiness of bees in this selection program is the only reason that he is still in business. His family-run business has been in operation for 40+ years.
One of our participants, Dave Shenefield, was able to use this project to leverage funding from the Indiana State Department of Agriculture to promote the adoption of more mite-resistant stock in Indiana, and to teach beekeepers how to raise their own queens, and select for good traits. Three instrumental insemination devices were purchased with these funds. Approximately 1,500 queens from this breeding project have been distributed each year, either in the form of a queen cell from which a queen will hatch, or a mated queen.
Areas needing additional study
1) There is a critical need to continue this selection program because as soon as this labor-intensive breeding is discontinued we will begin to lose these traits. There is not enough economic incentive or time for commercial queen breeders to perform these selections and instrumental inseminations.
2) We must combine multiple mite-resistance traits in northern-bred bees.
3) Study the genetics of mite-grooming behavior to determine if there are costs associated with the behavior that might impact bee health or honey production.
4) We must continue to encourage “micro-breeder” hobbyists and commercial beekeepers to raise their own queens and select for these traits.