A Sustainable Approach to Controlling Varroa Mites of Honey Bees

Project Overview

Project Type: Research and Education
Funds awarded in 1999: $86,286.00
Projected End Date: 12/31/2001
Matching Non-Federal Funds: $25,000.00
Region: North Central
State: Minnesota
Project Coordinator:
Marla Spivak
University of Minnesota

Annual Reports

Information Products


  • Animals: bees


  • Animal Production: parasite control, preventive practices
  • Education and Training: demonstration, farmer to farmer, on-farm/ranch research, participatory research
  • Farm Business Management: new enterprise development, cooperatives
  • Pest Management: genetic resistance, integrated pest management
  • Sustainable Communities: partnerships, public participation, sustainability measures


    Honey bees bred for hygienic behavior demonstrate good resistance to diseases and partial resistance to the parasitic mite, Varroa destructor. Bees bred for “Suppression of Mite Reproduction” (SMR) demonstrate better mite resistance than hygienic bees or bees imported from Russia by the USDA. We began testing reciprocal crosses between hygienic and SMR traits to increase mite resistance while retaining disease resistance, high honey production and brood viability. Our outreach program has been successful in transferring the resistant queens and breeding technology to beekeepers with the goal of reducing the use of pesticides and antibiotics within honey bee colonies.


    Honey bees, Apis mellifera, are the primary pollinating insect in North America. With the introduction of the parasitic mite, Varroa destructor, into the U.S. in 1987, the number of feral and managed honey bee colonies has decreased significantly. These mite pests have had a devastating effect on honey bee colonies and beekeeping businesses. To control V. destructor, beekeepers have resorted to the in-hive use of pesticides. For almost ten years, these mites were controlled successfully with the synthetic pyrethroid fluvalinate (Apistan“), applied as plastic impregnated strips within the hive. However, in recent years, the mites developed resistance to this compound. Most states now have Section 18 approval to use coumaphos, an organophosphate, as an alternative to fluvalinate, but this summer (2001) mite resistance to coumaphos was demonstrated in Florida (P. Elzen, pers. comm.).

    Another recent development since this proposal was funded is the spread of a devastating disease of honey bee colonies, American foulbrood (AFB), caused by the bacterium Paenibacillus larvae larvae. Most colonies infected with AFB eventually die and the spores left in the wax comb remain highly infectious for over 50 years. Until two years ago, this disease was controlled successfully with the antibiotic, oxytetracycline (Terramycin“). However, the incidence of AFB resistant to oxytetracycline has spread dramatically (Miyagi et al. 2000). New antibiotics are being tested for control of this disease, but they are not available to date.

    The goal of our research has been 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 V. destructor from among their own lines of honey bees and limit the use of pesticides within their colonies. Since 1994, we have been breeding bees for hygienic behavior. Hygienic behavior is one of several mechanisms of honey bee defense against the Varroa sp., both in the original host of the mite, Apis cerana in Asia, and in its new host, A. mellifera (Boecking and Spivak, 1999). Varroa sp. mites spend a portion of their life cycle feeding on adult bees, and the other portion reproducing and feeding on the hemolymph (blood) of worker and drone pupae within wax covered cells. Bees that display hygienic behavior are able to detect a portion of the mite-infested brood, uncap the cell and remove the infested pupae (Spivak 1996). The mother (foundress) mite may escape during the removal process, but her offspring in the cell are destroyed by the bees. Thus, hygienic behavior reduces the reproductive potential of the mite.

    In addition to mite resistance, it has long been known that bees that express hygienic behavior have the ability to detect, uncap, and remove diseased brood from the nest. In so doing, they remove the innoculum before the causative organism reaches the infectious (spore) stage (Woodrow and Holst, 1942). In early research, hygienic behavior was found to be the primary mechanism of resistance American foulbrood (Rothenbuhler, 1964), and also to another disease, chalkbrood, caused by the fungus, Ascosphaera apis (Gilliam et al., 1983). In research not directly funded by SARE, but related to this proposal, we tested whether our hygienic line, which is derived from different bees than the early studies, was resistant to AFB. We challenged hygienic colonies with spores of P. larvae larvae that were resistant to Terramycin, and found that 11% of the hygienic colonies had clinical symptoms of AFB by the end of the experiment vs 89% of the non-hygienic colonies (Spivak and Reuter, 2001). In addition, the hygienic colonies had significantly less incidence of naturally occurring chalkbrood disease. Thus, our hygienic line demonstrates a high level of resistance to both diseases.

    The focus of my research funded by SARE since 1997 was to determine if bees bred specifically for hygienic behavior would have sufficient resistance to the mite to reduce the frequency of pesticide applications in commercial beekeeping operations, and thus save beekeepers money. In collaboration with beekeepers, we tested the hygienic bees in commercial apiaries over two large-scale field studies. Our results indicated that colonies headed by naturally mated hygienic queens from the breeding program had significantly fewer V. destructor, less disease, and produced more honey than unselected, commercial colonies for up to one year without treatment (Spivak and Reuter, 1998; 2001). However, when mite infestation pressure was high (e.g., in migratory beekeeping operations when hundreds of colonies are moved together on trucks to a new location), the rate of removal of infested brood by hygienic bees could not outpace the rapid mite population increase, and the hygienic colonies required more frequent treatment to prevent collapse.

    To resist V. destructor, bees must have heritable mechanisms of reducing the survivorship and/or reproductive success of the mites. Although hygienic behavior is one heritable mechanism of resistance, other research suggests that the suppression of mite reproduction on worker brood may be a more important mechanism of resistance (Camazine,1986; Harbo and Hoopingarner, 1997, Harbo and Harris, 1998). The reduced fertility has been attributed to a genetic characteristic of the bee, but the mechanism is still unclear. With this round of SARE funding, we initiated studies in which bees bred specifically for Suppression of Mite Reproduction (SMR) were crossed with bees bred for hygienic behavior with the goal of increasing mite resistance while maintaining disease resistance and high honey production.

    Selection for resistant bee stocks has obvious importance for the health and survival of honey bee colonies, but until we began our research and extension efforts to promote the use of resistant (hygienic) stock, beekeepers were not interested in bees bred for resistance because it was simply easier to apply antibiotics and pesticides than to maintain selected lines of bees. The combination of the development of resistance to the treatments and our persistent research, extension and education efforts are finally motivating beekeepers to maintain and use resistant lines of bees rather than relying solely on pesticides and antibiotics.

    Original Objectives
    1. Continue the breeding program for honey bees that display hygienic behavior, one mechanism of resistance to the mites
    2. Screen hygienic line of bees for other mechanisms of resistance to V. destructor
    3. Test strategy of combining mite resistant bees with alternative treatment to limit use of conventional pesticides
    4. Conduct survey on performance of hygienic colonies in commercial apiaries

    Project objectives:

    1. Continue the breeding program for honey bees that display hygienic behavior, one mechanism of resistance to the mites
    2. Screen hygienic line of bees for other mechanisms of resistance to V. destructor
    3. Test strategy of combining mite resistant bees with alternative treatment to limit use of conventional pesticides
    4. Conduct survey on performance of hygienic colonies in commercial apiaries

    Any opinions, findings, conclusions, or recommendations expressed in this publication are those of the author(s) and do not necessarily reflect the view of the U.S. Department of Agriculture or SARE.