Back in mid-March we attended the Michigan Beekeepers Association spring conference and fully intended to make a few follow-up posts about what we learned, even as we knew it unlikely that we would follow through on the follow-up. Yet here we are, goaded into action by the discovery of this delightful graphic summary of Dr. Meghan Milbrath‘s talk on keeping bees healthy from Water Street Academy1. As you can see (if you zoom in) Dr. Milbrath covered more than just varroa.
Yet varroa remains the foremost concern of beekeepers in most parts of the world and it has been interesting seeing the consensus expert opinion on varroa change over the years at conferences. At one of our first the keynote speaker practically scolded the audience that they would have to seriously treat for varroa and that breeding bees to be resistant to varroa was as foolish as breeding sheep to be resistant to wolves. The audience meanwhile had a number of members sullenly unwilling to put miticides (the only treatments then available) in their hives, particularly when the mites kept developing resistance.
A few years later there was much talk of the Bond method or Live-and-Let-Die. Non-professional beekeepers were encouraged to let susceptible hives die and make splits of their surviving colonies. Slowly the number of surviving colonies would increase and one’s beeyard would become full of hives requiring no treatment. This worked for some although the same bees introduced to other beeyards proved as vulnerable as before. And the very many colonies that failed died a cruel death and could become “varroa bombs”, spreading hordes of mites by hitching a ride on robbers from the surrounding colonies. Nowadays this draconian approach is seen as being a poor steward to the bees and a poor neighbor to the surrounding beekeepers.
The current prevailing opinion is to monitor mite load and only treat when it gets too high2, rotating through treatments to prevent development of immunity in the mites and noting which colonies seem to maintain low levels without help. If some colony requires constant treatment to avoid succumbing to varroa then requeen it from resistant stock. This can be from your own hives or commercially available lines such as the Purdue ankle-biters3 or Minnesota hygienic bees.
Monthly checking is recommended and, of course, after any treatment to check its efficacy, but at the very least in spring before brood-rearing begins in earnest and in late summer or early fall, when varroa population tends to peak just as the fat, long-lived “winter bees” are being laid. A heavy mite load will decrease the longevity of these bees intended to last until spring, risking a dead colony for the next year.
We conclude with the results of our own sugar roll of yesterday.
|Hive||Mites per Hundred Bees|
Happily these are low enough that we need not worry about treatment yet.
1Proofreader can not resist pointing out that it should be whose tools and varroa.
2The recommended threshold for treatment has varied over the years. We use three mites per one hundred bees.
3The official name seems to have become the humorless “mite-biters”.