This method of varroa control using hive splitting was developed by Dutch researchers, and is based on both the theoretical model of varroa population growth and techniques for biotechnical control of varroa that originated in Vietnam (see 12.6). The method should be used during swarm control in the late spring/early summer, or when making ‘autumn’ splits in the late summer while the honey flow is on.
• Choose two colonies.
• Place a comb with empty drone cells in the centre of the brood nest of one colony (colony A).
Step 2 (one week later)
• In colony A, shake all the bees off the combs with brood except the drone comb, and put the brood in the other colony (B), after first checking for AFB.
• Put a second, empty drone comb in the centre of the brood nest of colony A.
• Put the queen in colony B above a queen excluder in a further super with empty combs.
Colony A now only has a single frame of uncapped drone larvae and an empty drone brood comb, while colony B has a two super brood nest plus a third super containing the queen.
Step 3 (one week later)
• Remove the comb that now has capped drone brood (and mites) from colony A (the comb that contained uncapped drone larvae the week before). The comb can be uncapped with a knife or cappings scratcher and the drone pupae can be removed from the comb in a small hand extractor, washed out with a hand spray nozzle attached to a garden hose, or simply shaken out on the ground. Drone pupae make excellent chicken feed.
• Put this cleaned comb (or another clean drone comb) into the centre of the brood nest of colony A.
• Shake all the bees off the new brood that has been produced above the excluder in colony B. The brood is all too young to contain any mites. Move the brood to colony A, after first checking for AFB.
• Take the bees and queen from the excluded box in colony B and make a broodless split (colony C). Shake all the bees off the second drone comb in colony A (now containing uncapped larvae), and put it in the centre of the super of colony C.
• Put a protected queen cell in colony B.
Step 4 (one week later)
• Shake the bees from the drone comb containing uncapped drone larvae from colony A, and place it in the centre of the brood nest of colony B.
• Remove the comb that now has capped drone brood (and mites) from colony C and destroy the pupae (see Step 3).
Step 5 (one week later)
• Remove the comb that now has capped drone brood (and mites) from colony B and destroy the pupae (see Step 3).
• Check colony B for a new laying queen.
According to the field trials carried out by the Dutch researchers, on average this method is 83.4 to 93.4% effective in removing mites from all three colonies (depending on the amount of drone brood available for trapping). The researchers have managed 70 colonies using this method for 5 years in Holland without using any additional, chemical control.