A nasty end-of-season surprise from Varroa
After all the talk about this being a bad year for varroa in northern Europe, I received quite a shock last weekend when I inspected the varroa screens after the two-tray (four week) treatment regime of Apiguard.
As is common with Apiguard treatments, the first tray treatment produced only a small varroa drop. However, as the Apiguard took effect and as the emerging brood exposed more mites to the treatment, it must have been raining varroa!
I would guesstimate that the total mite drop was about 1000 — which is just at the danger threshold guideline set by FERA in the UK (in Europe and parts of the USA, the thresholds used is sometimes 3-4,000). I use one varroa monitoring screen in each of my apiaries and each apiary, 4 kms apart, showed similar results.
From this I take two lessons:
- Apiguard is working
- never be complacent about varroa mite levels — just because there is little evidence of their presence in a colony, they can be there in force ready to wreak havoc when circumstances conspire.
If those colonies had not been effectively treated this year, I dread to think what would have happened during the course of next year when the varroa levels would have started at a very high level. As it is, some varroa mites will always escape any treatment and live to breed in the next season. In my colonies I would expect that the starting number next year will be low.
(Incidentally, the knock-down from treatment with Apistan tends to show up much earlier, and large mite falls can be expected even in the first 24 hours — treatment should however be continued for the six-week period to make sure that the mites breeding in brood cells are killed.)
Turlough, Vita’s Guest Beekeeper Blogger