Monitoring mites with a sticky board
A lot is written about how to monitor mite loads with a sticky board. A sticky board is just a piece of thin wood or corrugated plastic that is covered with a sticky substance—usually pan spray—and placed below a screened bottom board. A certain number of mites drop off and stick to the board. The board is usually left in place for one to three days and then the mites are counted so that a “24-hour mite drop” can be calculated.
Some beekeepers use this magic number to decide if and when to treat for mites, but ideas differ about what this number should be. As an example, the Brushy Mountain Bee Farm site suggests treating for mites if your 24-hour sticky board count is greater than 5-10 mites in the spring or 50-60 mites in the fall. Some sources use just one number. The Virginia Cooperative Extension site reads, “If more than 40 mites are recovered [in a 24-hour period], then the colony should be treated.”
I have serious doubts about the validity of these numbers. The most obvious problem is that they do not take the hive population into account. A mite count of 40 in a single-deep, five-frame colony is very different than a count of 40 in a triple-deep, 24-frame colony. Mites per bee is the important number, not mites per bee hive.
Mite drop in the fall is greater than mite drop in the spring because, in the spring, most mites are under the capped cells where they are not going to fall off. Brushy Mountain recognized this in their estimate, but Virginia Cooperative Extension ignores it. Neither site discusses differences in mite count seen in various subspecies of honey bee, or differences in counts due to local climate or latitude.
The way I see it, the best we can hope for from a sticky board is to give us an idea of increase or decrease in mite loads. Or, if a beekeeper is diligent about estimating colony strength, he can assess mite drop as a function of colony strength and from there, decide when to treat.
Like many issues in beekeeping, determining when to treat for mites is a skill learned by trial and error. It is nearly impossible to make “rules” that can be used successfully, although people keep trying. All beekeeping is local and all beekeepers are different. The main problem with teaching rules instead of concepts is that it gives new beekeepers false hope, and when they do everything the books say, and their bees die anyway, they wonder if it’s worth it.
So what do I do? No sticky boards. For the past six years I’ve treated for mites once a year with one of the thymol-based products. I do this in August when brood is low and while there’s still time to raise a crop of winter bees that haven’t been exposed to the thymol. I’ve had no problems with mites or mite-borne diseases until this year when I switched to HopGuard—but that’s an entirely separate subject. More on that later.