Varroa Mite

2021 October 17

So, as I’ve mentioned from time to time, I keep bees. And one of the recurring issues with honeybees is dealing with the varroa mites that infest them, and that eventually will become so numerous that they kill the hive. I last posted about my difficulties with them way back in 2007, and so I thought it would be good to revisit the topic.

Back on August 14, 2021, I checked for Varroa mites in my hives by using a variant of the “Powdered Sugar” method. Basically, what I do is take the hive apart, put each hive box onto a piece of butcher’s paper, and then sift a cup of powdered confectioner’s sugar over the top of the frames in the box. The bees get completely covered with sugar, and immediately go into a frenzy of grooming to get it off. This dislodges many of the mites that are present, which then fall down onto the paper along with some of the the sugar. After about 15 minutes, I take the hive boxes back off of the paper and restack them into a hive. Then I brush the sugar off of the paper into a bowl, add water to dissolve the sugar, and any mites present float to the surface of the water where I skim them off and count them. Here is one of them:


Mites are arachnids, with eight legs, although it is hard to see more than six in these pictures because the last pair tends to be hidden under the shell. The projection in front is, I think, the mouthparts. They feed on the bees by either riding on their backs or squeezing between the segments on their abdomens, and then probing through chinks in the exoskeleton to get at the bee’s body fluids.


Once they hunker down on the bee, they are rounded and fit smoothly onto their skins, making it hard to groom them off.


They also have funnel-shaped sucker tips on their feet, which help them to hold on to the bee. This is where the powdered sugar comes in. When the bee gets all sugar-coated and is trying to groom the sugar off, the mite is trying to use these suckers to hold on. But if the suckers get coated with powdered sugar, then they can’t get a good seal around the edges of the suckers, and they lose their grip and fall off.


So, anyway, since 2007 I have had a lot of ups and downs with the mites, generally they have wiped out all my bees over the winter every 3 years, regardless of mite treatments. But now, things seem to be coming together. What I have done, in order, is this:

1. Late in the summer, break up the hives into 2-box nucleus hives, and powder them with sugar to check for mite levels. The nucleus hives then have to raise a new queen, and the break in brood-rearing keeps the mites from reproducing (the mites need bee larvae to breed on). The nucleus hives then have only a moderate number of mites.

2. The nucleus hives are then too small to overwinter outside, so I move them down into a cellar around November 1. The cellar keeps them at a moderate temperature that is low enough for them to make a winter cluster, but not so low as to keep the cluster from accessing all the stored honey in the hive. I can also go into the cellar with my stethoscope and the thermal camera on my phone to check on how they are doing. If necessary, I can even give them supplemental frames of honey or sugar syrup. They then come out of the cellar after the snow starts to melt and the maples bloom. In the past, I experimented with giving them a bit of electric heat to take the edge off of the cold, but the last couple of years have shown that supplemental heat is not necessary as the cellar is generally hovering right around freezing (not all that cold as these things go)

3. For the last few years, I have been running the “Saskatraz” strain of bees. These were bred up in Saskatchewan, Canada, and have been selected both for overwintering ability and for varroa mite tolerance. This is coming up on my third winter with these bees, and they seem to be doing better than previous strains.

So, when I was testing the bees for mites with the powdered sugar, this year I only found one or two mites per hive, which is way down from the 20 to 50 that I used to find in the past. This is extremely encouraging, this is the winter where I would normally expect the mites to get out of control and kill the bees. The big question is, how are they going to do this winter?

One Response
  1. Kathleen Bradley permalink
    October 19, 2021

    This is great. I am going to share with my beekeeper friends.

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