Towards integrated control of varroa: 3) mortality proportion from early spring trapping in drone brood

Abstract

We determined the proportion of varroa mites, Varroa destructor, in capped drone cells in southern England in spring, when drone rearing was beginning and was at a high level. We introduced two separate test frames of foundation (2/3 drone cells and 1/3 worker cells) into 20 honey bee hives, the first on 2 May, when drone rearing was just starting, and the second on 3 June 2013. Varroa populations were determined per colony by extracting mites from samples of worker bees, and from sealed drone cells and sealed worker cells in the test frame, and from additional samples of sealed worker cells. Samples were collected three times on 2 May, 3 June and 28 June. Colony populations were estimated from photographs of frames of bees and brood. The drone cells in the first and second test frames represented 14 and 11% of all capped brood cells (drone + worker combined) and trapped 44 and 48% of all the mites in the colonies, respectively. Sealed drone cells had 13 times as many mites as sealed worker cells, on average. We conclude that trapping in drone brood is not very effective in controlling varroa within bee hives, even when carried out in early spring with a trap frame that allows all the capped drone cells in each hive to be removed. By reducing a colony’s varroa population by 46%, slightly less than one population doubling is needed to restore the varroa population to its previous level. In the study area varroa populations double c. 5–6 time in one year. Thus, the duration of control from one month’s drone trapping is only 2 months.