A Sustainable Approach to Controlling Mite Pests of Honey Bees
The objectives of the project were as follows:
1) Augment the existing honeybee breeding program by increasing the number and genetic diversity of honeybee colonies that display hygienic behavior;
2) Compare the mite loads and survivorship between untreated hygienic colonies from the breeding program and untreated colonies from commercial (control) stock;
3) Continue testing alternative treatments for the Varroa mite. We were not able to obtain reliable results from objective 3; therefore, we focused instead on a new objective:
4) Compare colonies from hygienic and non-hygienic lines for resistance to the most serious bee disease, American foulbrood. This study was important because in the last two years, the bacterium causing the disease developed resistance to the only registered antibiotic used to treat it, and finding an alternative solution to the disease problem was critical.
The number one priority of the beekeeping industry in the U.S. is to control the parasitic mite, Varroa jacobsoni. Since its introduction into the U.S. in 1987, Varroa has destroyed virtually all of the feral honeybee colonies and a high percentage of the commercial colonies, negatively impacting fruit and vegetable pollination and threatening the vitality of the beekeeping industry nationwide. Varroa mites can be effectively controlled with the registered pesticide fluvalinate (Apistan ®) or the organophosphate coumaphos (CheckMite ®), but routine use of these pesticides within bee colonies has the potential of contaminating honey and beeswax. Recently, the mites have developed resistance to fluvalinate in various regions throughout the U.S.
The most sustainable, long-term solution to control the mites is to breed honeybees that demonstrate natural mechanisms of defense against the mite. Such a breeding program was initiated at the University of Minnesota by Marla Spivak in 1993 and has generated very promising results. Colonies were bred for hygienic behavior, a defense brood from the nest, interrupting the mites reproductive cycle and mitigating the spread of disease.
The results of the study relative to objectives 1, 2 and 4 are as follows:
1) The number of genetic sublines within the hygienic lines of bees was increase from 5 to 11 in the last three summers. There is now sufficient genetic variation within the line so that it can be maintained without the threat of inbreeding.
2) A large field study was conducted to compare hygienic and commercial (unselected) colonies in collaboration with Pete Vos, a commercial beekeeper in Minnesota. The results demonstrated that after one year without treatment, the hygienic colonies had significantly lower levels of Varroa mites across all apiaries, while producing as much honey as the commercial line. We conclude that hygienic colonies will require fewer treatments for Varroa than unselected stocks of bees, which is highly encouraging.
4) Over two summers, 1998 and 1999, the hygienic colonies demonstrated good resistance to American foulbrood, which would reduce antibiotic use in honey bee colonies.
Our goal was to breed bees that could resist Varroa and diseases sufficiently to decrease the reliance on pesticides and antibiotic use within bee hives, and to transfer the breeding program technology to producers so they can take responsibility for reducing chemical use through continued breeding efforts. Any reduction in the use of expensive pesticides and antibiotics means increased profit for the beekeeper, and will help ensure the purity of honey and hive products, while maintaining healthy bee colonies critical for pollination of crops, gardens and wildflowers.
For more information:
Department of Entomology
1980 Folwell Ave.
219 Hodson Hall
University of Minnesota
St. Paul, MN 55108