There is growing evidence that colonies are surviving without the intervention of chemicals and we in the Tavistock branch are searching for local strains that have desirable hygienic behaviour that allows them to live alongside the parasitic mite.
We are convinced that varroa tolerant bees will exist in the West Devon area and we are approaching all members of the branch to help us screen their hives for Varroa sensitive hygienic (VSH) behaviour.
The initial screen will consist of a pin-prick test of 50 pupae followed by an inspection 24 hours later to see how many damaged pupae have been removed by the worker bees. Any colony with greater than 70% removal of damaged brood will be considered for stage 2. Stage 2 will consist of opening up 50 capped larvae (day 18 red-eye stage) to see the developmental stage of varroa mites within. All colonies that have good VSH behaviour will score highly in this test but not all colonies that uncap will have the other traits that contribute to the ‘search and destroy’ behaviour that we desire. In a colony with good VSH behaviour there will be evidence of an interrupted varroa reproductive cycle. (reference)
Once we have identified candidate colonies, we will selectively breed from these and attempt to set the trait in a population of bees. We are currently of the opinion that instrumental insemination may help us in this endeavour, using semen from single drones from candidate colonies. For instructions on home-made instrumental insemination kit click here