varroa mites

Don’t miss the Varroa train

This post, bound to be wildly unpopular, is a reminder about Varroa mites. At this time of year, when colonies are large without a mite in sight, it’s easy to underestimate them. But like a terrorist cell, they work in secret. They know their time will come.

During spring build-up of honey bee colonies, the bees out-produce the mites. But come late summer when drone production stops and worker production slows, the mites will out-produce your bees. If you are not ready for the reversal, your hive may not survive till spring.

It is hard to make winter preparations in the heat of the summer. But if you wait until October to think about overwintering, you will have already missed the Varroa train. In fact, there will be no seats left on the train after August—they will be claimed by hoards of mites doing their best to kill your colony.

If you want a reasonably good chance of seeing your bees in spring, you need to finish your winter preparations in just a little over three months from now—about 14 weeks.

“How can that be?” you wonder. Well, here’s the thing to remember about Varroa mite treatment: How you treat is up to you, but when you treat is not. Here’s why:

Summer honey bees live four to six weeks, but winter bees can live six months or more. The winter survival of your colony is directly dependent on the health and vigor of those winter bees. If they are weakened by mites or viruses, your colony has little chance of survival.

But it’s your summer colony that has to raise the winter bees. To produce a healthy winter population, they must raise winter bees in an environment free of both Varroa mites and the diseases they carry. The winter bees will be raised in September or October, which means that in most of North America, your colony needs to be virtually mite-free by the first of September.

Now is the time to decide on a treatment regimen. Many options are available from powdered sugar to organic acids to commercial pesticides, as well as various management strategies such as drone trapping and hive splitting. I urge you to read about the pros and cons of each and to avoid commercial pesticides whenever possible.

Regardless of the option you choose, you must make a plan. For example, using powdered sugar alone requires weekly applications from now till winter, so you need to get started. If you plan to use one of the organic acids, you may need to order the product and accumulate the necessary equipment and know-how. If you are going to trap drones or restrict egg laying, now is the time.

So yes, I know it’s only May, but if you want to derail the mites before they rule your winter hive, it’s not too soon to start.



    • Aram,

      What temperature are you using? Also how are you regulating it? I don’t know anyone who has used the heat method. Thanks.

  • The method is generally used in conjunction with queen isolation cages, or with nucleus colonies, since all of the worker brood is treated. Studies show that if the brood is heated to 44°C for 4 hours, 100% of the mites in the capped brood will be killed. Only about 5% of the brood itself is killed in the process, mostly in the form of older larvae that crawl out of the cells. Heat can also cause some deformities in adult bees that develop from old pupae that have been treated. There is no noticeable affect on the life-span of bees emerging from heat treated comb.

    Source: Control of Varroa (a guide for New Zealand beekeepers)

  • Forgot to mention. I will be using a deep body into which I will place a weak space heater with fan. Then I will add a deep box with frames, probably spaced out 9 frames or less to a box. Then I will place a gabled roof like you described in your overwintering setup, so that hot air could exit through front and back holes. On top of the gabled roof I have an installed thermostat with a probe that will go either between or inside the brood frame.

  • Rusty:

    Any suggestions on the application method of powdered sugar? Is it just sprinkled into the brood/honey supers? A weekly application is understandable but does this interfere with the honey harvest?


    • Rich,

      Both sides of every brood frame has to be covered. The best way to do it is with a bellows or a similar system that makes a cloud of sugar that goes everywhere. When done correctly, you will be white bee “ghosts” flying around the hive.

      I’m sure some amount of sugar makes its way into the honey. Powdered sugar is good way to keep your bees away from chemicals, but there are compromises, and sugar in the honey is one. It also creates a high degree of hive disturbance. There is no perfect answer to the varroa problem.

  • Rusty, it may not be the most popular post ever, but it may one of the most timely. Everybody has their new packages installed, they’re adding brood boxes, setting supers on their survivor hives, and “hoping for the best” or “crossing their fingers.” Now is the time to get their attention!

    We are planning an August presentation specifically on fall inspection and minimizing winter losses, and trust me, your advice here will be way up at the top of the list.

    As for powdered sugar: I used it with a small one-hand-held flour sifter, which are still available from both homestead suppliers and good kitchen outfitters. I just made sure a thick dusting went between each pair of frames, and repeated ten days later. At that time the colony was in a medium and deep, and I took the medium off to treat the deep. It seems to have worked, because that was June, and they came through winter with no trouble, and absolutely exploded, population-wise, this spring.

    Once again, if you have a small digital camera, nothing beats snapping shots of every frame of bees you inspect, blowing the image up to 200% and scanning every inch, which is how I found my mite problem, and also monitored for results. It’s a lot of work, but two beekeepers can help each other, and it’s worth the effort. We’ll be doing this again (the pictures that is) when most of the drone brood emerges.

    Thanks and keep reminding us!

  • I know the powdered sugar option is popular because it is organic, but unfortunately it doesn’t work that well. New to beekeeping, I was on board with the sugar method until a local beekeeper said this to change my mind: “If someone put a leech the size of a dinner plate on your back, which treatment would you rather have: an organic but ineffective one, or a fairly gentle chemical that gets the leech off your back?” I took his point to heart: Varroa mites = suffering for our bees. My partner is a beekeeper and he treats with Thymol, which is a mint-based fumigant. Depending on how you apply it is quite effective, and has minimal impact on the hive in terms of harm to bees. Until they find a more effective organic treatment, I’m going to shut my mouth about the Thymol and other treatment options that get those leeches off our bees’ backs!

  • This may seem like a silly question but do you treat (let’s say with powdered sugar) if you see no signs of mites? We installed two nucs this spring and while we have a few small hive beetles (homemade bait trap working well) we’ve seen no signs of mites. Would you try the powdered sugar just in case or wait until you actually see the little buggers? Thanks!

  • Rusty do you ever use vaporized oxalic acid in USA? Natural and very cheap with no harm to the bees but very affective against killing mites,applied in mid winter without opening the hive so very little disturbance to the bees.

    • Sean,

      Since oxalic acid is not an approved treatment for mites in the US, I don’t recommend it. But I have used an oxalic dribble with excellent results. I have never tried the vaporized method.

  • Rusty, I use the vapourizer method over the drizzle as there is no harm to the bees as no ingestion of oxalix acid and can be used multiple times with no ill effect on brood bees or queen and classed as organic in the UK. Maybe it comes down to big business in the USA as the oxalix acid is so cheap? Regards Sean

    • Sean,

      Yes, I’m sure that is the reason. It costs a lot of money to get approval of a substance here in the States. Oxalic acid is cheap and readily available so there is no financial incentive for anyone to get it approved. It’s very sad, actually.

    • Duane,

      Powdered sugar does not need approval by anyone because it is a substance that is generally recognized as safe. (GRAS)

  • Queen isolation/brood break…

    Say I would like to force a brood break in my hive – would it be possible to accomplish this by trapping the queen under a small isolation cage, on the comb, for a period of time? Would her retinue be able to tend to her (the cage I have on hand would not be large enough for attendants)? How long would I keep her there? Would it attract the mites to the queen since she could only lay in a small area? I do not want to do a split. If this is a bad idea, what is the best way to remove her without killing her?


    • Kendra,

      I’ve heard that if you place the queen in a cage the colony will raise a new one because they see their original queen as defective. I usually do brood breaks by putting one frame and the queen in a nuc, and letting the original colony raise a new queen. If it is successful, you can use the old queen somewhere else, or you can re-introduce her if their efforts fail. You will need to use standard introduction techniques because they will not “remember” her.

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