BRAMBLINGS – the occasional newsletter of NCBKA

Resistant Varroa Mites

A few years ago beekeepers were anxiously waiting to find out whether Varroa would spread throughout the country and affect everybody’s colonies (it has and it has). We are now entering the next phase of the story since significant levels of resistance to standard anti-varroa treatments has now been confirmed by the Central Science Laboratory. So far, resistance has only been confirmed in one apiary in Devon, but the problem is severe since test strips of Apistan were found to be only 2% effective. Apistan and Bayvarol are normally 95-100% effective and hold mite levels below the threshold at which the colony is threatened

A DIY kit for testing your own colonies for Pyrethroid resistance in Varroa mites has been developed and we hope to have information ready for the 22^nd September apiary visit. In the meantime, do not neglect anti-Varroa precautions. Be very wary of claims that it is easy to develop your own strain of Varroa-resistant bees. If you are tempted to use Continental treatments which may appeal to the “organic” preference of many of us, remember that they have not been authorised for use in the UK and are not necessarily appropriate in our climate and circumstances. Remember also that the active constituents of Apistan and Bayvarol are the same pyrethroid and so switching from one to the other is not equivalent to switching between antibiotics. If you have fewer than 5 colonies use Bayvarol since each treatment is individually packed. Avoid using Apistan from a foil packet that has been open for a long time. Store your strips away from heat. The ideal time for routine treatment is the end of August so that the strips are removed in mid-October (It is not too late to put strips in now, but the later they go in, the worse the weather is likely to be when they come out. The most serious mis-use is leaving the strips in the hive for too long. Always read the instructions – they may change from year to year!

Apistan and Bayvarol consist of the active pyrethroid held in the polymer strip. As bees pass over the strip they pick up a dose which kills the mites and causes them to drop off. As pyrethroid is used more diffuses to the surface. Quantities have been calculated to give the right dose to the entire colony of bees over the specified period (6-8 weeks). Instructions are ambiguous about the number of strips required if bees occupy more than a single brood box. I am seeking definitive advice on this.

We have several prospective new members as a result of the recent publicity linked to our own “free-bee project”. Subscriptions are now due and we shall soon know how many inquirers join up and become active beekeepers. Subscriptions are due in October for the year 2001/2002. £20 if paid before 30^th November, £21 for late payment. In addition, everyone who has bees should take out Bee Disease Insurance at £1.20 for up to two colonies. BDI covers loss due to Foul Brood diseases (not Varroa!) and is well advised since there have been recent outbreaks of Foul Brood just to the North of us.

May I take this opportunity to welcome the newcomers to beekeeping and the North Cotswold Association?

Will Messenger, 8^th September 2001