The Oil Drum

I attended our local beekeeper's school this weekend, and one of the big entomology experts from NC State was there to talk about various bee diseases, parasites, etc. We got a good state-of-the-art briefing. He didn't even mention using plastic combs, probably for the reason that you discovered.

Actually, plain old confectioner's sugar holds great promise. Seems that the mites can't keep their grip on the bees when they are coated with confectioner's sugar. They fall off, and can thus be removed from the bees. Since it is sugar, for the bees it is a feast.

This procedure is used on a small scale now in order to get an approximate count of mite infestation. If one were to get most or all of the bees into some sort of cage (probably using a one-way passage like what is used to clear a super for harvesting), they could then be dusted in the cage, the mites would fall out of the bottom with the extra sugar, and then you return the miteless bees to the hive. There is research going into such a scaled-up approach right now, and it looks pretty hopeful.

Using the larger cell foundations to encourage the laying of drones to trap the mites (which lay preferentially on drone larvae) - you pull out the frame before they emerge and either freeze them, or let them emerge within a cage and dust them with sugar per above before returning to the hive -- is another approach. It helps, but even repeating it almost constantly won't do much more than keep the mite population down a bit.

The screened bottom boards reduce Varroa mite populations by about 10%. That by itself is probably not going to be quite enough, but every bit helps, and it is an easy thing to do.

With each generation, some strains of bees are becoming more resistant. With a little bit of intelligent help, they can eventually be pulled through and this will become a relatively minor problem.