Report for FS04-181
The honey bee tracheal mite, Acarapis woodi, was introduced into the United States in 1987 and is now a widespread parasite throughout North America. Infestations of colonies of honey bees by tracheal mites dramatically increase bee mortality as well as severely reduce the productivity of honey bee colonies. Tracheal mites affect the ability of honey bees to survive through the winter and can be a major cause of colony loss in the South. Effective chemical treatments are available to control levels of tracheal mites in bee colonies. Beekeepers are constantly faced with the need to introduce more and more chemicals into their colonies to combat resistance to treatment. This not only adds to the cost of producing honey bee products, placing the American commercial beekeeper in a competitively unfavorable position, but also increases the likelihood that unwanted chemicals find their way into these products and the environment. The mechanism of resistance to tracheal mites is not known but may be related to honey bee-grooming behavior that inhibits transfer of mites from old to young bees. The spread of diseases and parasitic mites poses a major threat to the adequate pollination of our crop lands by honey bees. Pollination by honey bees is responsible for 15 to 30% of the food production in the United States. The number of managed honey bee colonies in the United States plummeted from 5.9 million in the late 1940s to 4.3 million in 1985 and 2.7 million in 1995. The goal of this project is the development of tracheal mite-resistant stocks of hygienic honey bees. Ample evidence exists from the studies cited above that genetic resistance to tracheal mites in honey bees is present. A stable genetic stock of honey bees that express tracheal mite resistance would be a cost effective and environmentally friendly means of combating this pest. However, in order for tracheal mite-resistant, hygienic queens to be attractive to beekeepers, they will also need to have other favorable behavioral characteristics for honey bees in the South. Among the latter, honey production, brood production, swarming and supercedure (queen replacement by the colony) tendencies, and temperament are the most important. One of the problems that has emerged with the development of honey bee stocks resistant to the parasitic mite, Varroa destructor, is variable expression of desirable behavioral characteristics. Thus, it will be important to identify and establish genetic stock that have favorable performance attributes for honey bees used in the Southern states along with resistance to parasitic mites and displaying hygienic behavior. Specifically, the objectives of this project are to develop honey bee queen stock that is genetically resistant to tracheal mites, Varroa mites, AFB; and perhaps, the African small hive beetle; to evaluate under standard beekeeping field settings the reduction in pesticide and antibiotic usage provided by genetically resistant queens. The goal of breeding mite resistant bees is to develop stock that have a significantly lower dependence upon chemical treatments for survival. Although the Baton Rouge Bee lab has derived some lines with tracheal mite resistance, these have not been optimized for hygienic behavior or other desirable behavioral characteristics. The initial goal of the queen breeding program is to identify four queen lines that express tracheal mite resistance, hygienic behavior, optimum brood and honey production, and gentleness. The need to have four queen lines is to minimize inbreeding problems by incorporating genetic variability into the breeding program. The breeding design will use a closed-population format in order to derive bees with the desired traits while maintaining genetic variability. The closed-population design can be accomplished by isolation or artificial insemination. With the exception of a few locations, breeding isolation is very difficult to achieve. Thus, instrumental insemination will be used to fertilize each of two queen lines with a pool of semen obtained from the same respective queen lines. Once tracheal mite resistance and hygienic behavior are confirmed in the progeny, field-testing under typical beekeeping settings will commence in the second year. This will be accomplished by enrolling three beekeepers from Tennessee, Kentucky, and/or Alabama in this study. These beekeepers will requeen 10 of their colonies with the resistant queens using 5 colonies for each of two resistant queens. The latter colonies will not receive treatment with chemical acaricides unless the level of Varroa populations necessitates medication. Sheets of sticky paper that fit into a bottom board of the hive are used to determine the number of Varroa present in a hive. The sticky board is covered with a piece of 8-mesh hardware cloth so that the bees will not come into contact with the sticky coating and be caught themselves. Delaplane and Hood (1997) have stated that bottom board inserts are the best survey method for making treatment decisions. For the Southeast, they have estimated a treatment threshold ranging from 59-187 mites on overnight sticky boards. This range represents 3100 to 4200 total Varroa mites in a colony. Treatment for Varroa will use Varroa-specific medications such as Apistan. In addition, collaborating beekeepers may choose to use biotechnical control methods for Varroa that include screened bottom boards. Whether or not screened bottom boards are used should not introduce a significant bias to the results since the efficacy of the latter in controlling Varroa may only attain 10%. Colonies with resistant queens will not be treated for tracheal mites during the course of the field trial. In late fall, coded samples of frozen adult bees from the participant’s colonies will be shipped to Backwood Apiaries in order to determine the presence and levels of tracheal mites. Beekeepers can then treat for tracheal mites if infestation levels based on the latter counts warrant treatment. Colonies managed by the beekeeper that do not receive tracheal mite-resistant, hygienic queens will be managed as he/she would have done normally in the past. Participants will also provide data on levels of Varroa infestation, incidence if any of AFB and the small hive beetle, whether screened bottom boards were used, and overall colony performance such as brood and honey production, gentleness, and swarming tendencies. However, honey production and swarming tendencies will predominantly reflect the preexisting characteristics of the recipient colony since requeening with resistant queens will not occur until late spring. The honey flow will be in progress at this time, which is also when swarming is most common. Following requeening, it will take approximately six weeks before the characteristics of the colony reflect the genetics of the resistant queen. The applicant does not believe that a clear indication of the honey production and swarming characteristics of colonies with resistant queens is a serious drawback. The genetic stock that will be used for the development of resistant queens has been selected over many years for optimal performance behavior. The main goal of the field trial is to show the collaborating beekeepers that queens with tracheal mite-resistant and hygienic behavior genetic traits substantially reduce pesticide and antibiotic dependencies. Backwood Apiaries will also requeen 10 of its colonies using 5 colonies for each resistant queen line. In addition, the colonies at Backwood Apiaries will be monitored periodically for the presence and levels of tracheal mites.