5.2. Resistant bees
Some races of bees are less susceptible to tracheal mite infestations. Resistance is accomplished in part by the increased autogrooming behaviour of bees (Lin et al., 1996; Pettis and Pankiw, 1998; Danka and Villa, 2005; Villa, 2006; de Guzman et al., 2002, 2005). Russian and Buckfast queens are among the more resistant lines of bees. Fig. 13 illustrates steps needed to select and propagate bees that show resistance to HBTM. Workers with 15-25% infestation in the autumn will not survive the winter. Bee stock can be screened for HBTM resistance to develop resistant queen lines. In general, untreated colonies that survive the winter with low mite numbers should be selected for a breeding programme.
- First, select colonies to be tested for mite resistance, and collect sealed brood frames.
- Brush off the bees clinging to the frame and place the frames into a frame cage (Fig. 13, insert) and then into an incubator set at 35ºC and 50% RH.
- Mark the frames to identify the test colony.
- After 12-24 hours in the incubator, remove and mark any emerging bees. Bees identified by coloured plastic tags or model paint can be separated by colony of origin and placed into an inoculation colony, where HBTM prevalence is high (>50%).
- After a week or more, the marked bees that were released into host colonies can be retrieved and dissected to determine mite prevalences (percent of mite-infested bees in the samples) or mite abundances (average number of mites per bee/total number of individuals of the host bees in the sample) for the bees from each test colony source. Original colonies that tested lowest for HBTM can then be selected for a breeding program. For more information on breeding and selecting traits in queen bees, see Büchler et al., 2013.
Fig. 13. Schematic diagram outlining a procedure to determine the relative susceptibility of honey bee colonies to HBTM infestation. Brood combs with emerging bees are brushed free of adult bees and then placed into frame cages (insert) or other containers to isolate bees; frames are placed into an incubator. After a week, emerging bees are marked and then placed into inoculation colonies. The marked bees are retrieved after a week and dissected to determine mite prevalences or mite abundances for the bees from each test colony source (from Danka, 2001). See text for explanation.