how to varroa mites

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 and a “24-hour mite drop” is 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.”

How good are the numbers?

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.

Learning by doing

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, and their bees die anyway, they wonder if it’s worth it.

So what do I do? No sticky boards. Instead, when I need to do a mite count I use one of the more reliable methods such as a powdered sugar roll or an alcohol wash. The results obtained give you an estimate of mites per bee, and these tests are considered to be far more accurate than the sticky board.

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 mite-vectored viruses. 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.


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  • Speaking generally of mite control, do you advise screen or solid bottom boards for nucs? Going into my second year of bee keeping and thinking of keeping some spare queens in a mating nuc.
    Love your site, sorry for your tree losses. Nature’s way of ‘pruning’ I guess.

    • John,

      I use screened bottom boards on everything, even nucs. I believe they are of marginal use for mite control, but they are a great source of ventilation. I never go without them.

      • My name is Keith I’m a new new keeper. I treated with Apiguard on 14 Aug and second dose on 3 Sept. I just did a mite drop count on 5 Oct and have a least 10 per day. Is that to many for this time of year to still have healthy winter bees?

        • Keith,

          There is no reliable way of knowing if that is too many unless you know how many bees are in the hive. What you need to do is a sugar shake or an alcohol wash so you can estimate the mite drop per 100 bees. The USDA site has excellent and easy-to-follow instructions for doing a sugar shake that will not harm any bees. With it, you can calculate the number of mites per 100 bees. Treatment is recommended at 3% (3 mites per 100 bees).

          The USDA site also gives instructions for using a sticky board, which works but which many beekeepers think is less accurate. However, if you follow the instructions exactly, the treatment level is 30 mites in a 24-hour period.

  • At my apiary we often use cut-down estate agents boards smeared with vaseline. It is fun finding hundreds of mites on there after treating with oxalic acid in the winter. Another use for the board can be seeing how big the cluster is and where they’re feeding from the pollen and wax cappings dropped down onto the board.

    Our National Bee Unit has a useful online varroa calculator at which takes into account the month of monitoring, brood rearing season and drone levels and advises whether you need to treat or not. It is UK oriented however as our colonies tend to be fairly small.

    • Hi Emily,

      Thanks for the link to the mite calculator. You bring up a good point about sticky boards–they can reveal a lot about the strength and location of your colony by just looking at the debris. Somewhere on this site I wrote a piece with photos of that very topic but, as keeps happening lately, I can’t find it. Anyway, I’m glad you reminded me. Also, I agree it is a good feeling to see mites stuck to the board–good riddance.

  • Is treating a captured swarm a good idea? There is no brood or honey. Seems like it would give them a clean start. Would it or would it damage them somehow?

    • Just make sure they are settled in real well before you do it, otherwise they might abscond.

  • Can you do any of this with a regular bottom board? I plan on getting screened bottom boards, but at the moment only have solid. I do have some sticky-boards already. Would I be able to put that on-top of the solid board and would I then need something on top of it, like perhaps netting material, so the sticky-board doesn’t disrupt the bees?

    • Robert,

      Something would have to be on top so the bees wouldn’t stick to it, but the screen or netting would have to be large enough so mites could fall through. It sounds like a hassle to me.

  • I have cut holes in the center part of my old, solid wood bottom boards and covered with screen (recommended by Ross Conrad in Natural Beekeeping, Organic Approaches to Modern Apiculture, p. 125). Then I added a rail on either side of the bottom board (nails along the edge would also work), and cut a stiff piece of cardboard to slide in and out. Another beekeeper showed me how to use a screw to screw in a halved wine bottle cork to act as a handle to easily pull the makeshift board in and out. It fits in the front. I am going to make some boards that are only 1/2 size, to give the bees some protection from cold, but also continue with ventilation. Hope this helps.

  • Hi,
    Have you done a post on the HopGuard switch? Of course now I’m curious.

    • Deb,

      Yes, there are several posts here on HopGuard, but none on HopGuard II, which I haven’t tried.

  • Rusty,

    I’m real late to this party, but could you expand on this sentence from your post?

    “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.”

    Is there a problem exposing the bees to the thymol? First year beekeeper and probably need to treat for mites.


    • Dan,

      I’m really glad you wrote because that statement from a very old post needed to be changed. It’s not the thymol that’s the problem, it’s the virus. You want to raise winter bees that have not been exposed to bee viruses. This statement, from a later post, explains:

      “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 and 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.”

      Even since I wrote that, things have changed a bit. Some of the academic sites are now recommending that mite treatment be completed by August 15 instead of August 30. It depends on how far north you are, but I now go by the newer recommendation.

      I’ve updated the post on sticky boards. Thanks for your help.

    • Deborah,

      In order to reduce the chances of mites developing resistance to treatments, it is necessary to rotate your treatments. I rotate between thymol, formic, hops, and oxalic.

  • I’m a first year beekeeper. I had a severe injury early August which has kept me from treating my bees for mites. I just treated them today with the MAQS. The outdoor temperature is perfect, but I’m concerned that I might be too late for healthy winter bees. I guess better to treat than not to treat. I was planning to do the 7- day treatment, but I’m wondering if I should do the 21-day instead, since they’ve had an extra 7 weeks for the mites to multiply?

      • Yes, I have sticky boards to monitor at 7 days.

        I actually placed a sticky board the afternoon right before my injury, so although it isn’t accurate, I can see the accumulation of mites since 8/13/17. I think that’s why I’m so concerned. Understandably the sticky board has been in a long time – 6 weeks – but it just seems like a very serious infestation. I’ve read that infestations this late into the season means that the colony will likely die during the winter due to other viruses carried by the mites.

  • Hi Rusty,

    Just had a quick question about mites. I am a first year beekeeper and I had started a thymol treatment on all 5 of my hives on September 5th. I then went on vacation for just under 3 weeks, and when I got back, 2 of my strongest hives were missing their queens. It was really strange, but I think I know what happened. While I was away, we had unusually warm temperatures (35+ Celsius or 95+ Fahrenheit for numerous days). I am thinking that the high temperatures and the thymol may have drove the queens out of the hive (because of the strong smell of the thymol). I was lucky enough to get 2 new queens and they have been accepted into their new hives. But while those queens were settling into their new home, I didn’t want to use any thymol treatments on the hives, in fear that I would lose the queens again. I have one hive that seems fairly infested with mites (and it is the one I am concerned about). I put a sticky board down and in a double deep hive (that is basically full), I collected 37 mites over 3 days. My question to you is, would it be possible to still treat this hive with any kind of treatment? The rest of my hives have a much lower count. Only an average of 2 – 5 mites collected over 3 days (and all the hives are basically full double deeps). There isn’t much brood left in any of my hives. I do have Apivar here at the house. But I thought it may be too late for Apivar. Any advice would be greatly appreciated!

    Have a great day and thank you for your informative website!

    • Nate,

      Treating for mites when there is little brood is ideal, so now is a good time. Temperature, as you already know, is one of the most important parameters when using any mite treatment. You need to go online and read the package inserts for any treatment you are considering. Just search for package insert, or directions for use, or something similar and you can find any of them, and they will give you temperature parameters. You mention Apivar, and I believe that would work just fine right now.

      Also, I would do a real mite count using a sugar roll test. It sounds like you still have a significant mite load.

      • Thanks! I am going to do that today. Would you advise treating all my hives with Apivar or just the one with the high mite count?

  • Hello Rusty,

    I hive a lively and healthy hive in Aberdeen WA and check on them regularly. On my mite monitoring board I have noticed a few dead mite bodies (shells) along with other normal wax debris etc. Otherwise they are very strong with plenty of winter stores. I treated with Apiguard in Sept. which resulted in less than 1% when checked (sugar roll) in October.

    Is the presence of Varroa in the winter normal (2 – 3 bodies/week) in a healthy hive?

    Also, my bees continue to bring in a light grey and pale yellow pollen, as late as last week. What could be the source of pollen in winter?

    Thanks in advance for your reply.

    • Larry,

      Yes, there are always varroa mites in hives. We never kill them all, so the few that remain start to reproduce. For winter, that drop rate sounds normal to me.

      I don’t know the source of your pollen, but it’s about time (early February) to begin seeing the spring crop. I’ve heard that pollen can be found nearly year round, but some of it is not as nutritious as the spring and summer stuff. It could be from cedars and ferns, which shed tons of it.

  • I treated with Apivar. Started August 15 and took off 42 days later. I put the mite board on for 24 hrs the day I took the Apivar off. I still have mites. A few days later I put the mite boards on again only this time I left them on for 3 days. when I took them off I counted the mites then divided by 3. I still had some mites but they were less than 50 per day. I can’t decide if I should treat again or not. And if I do treat how long should I wait since I just took the Apivar off approx. a week ago. Can you advise me on this? Thanks!

    • Linda,

      In many areas of North America, varroa mites have developed resistance to Apivar. Some people say it has become totally useless. Personally, I wouldn’t trust it. If I were you I would treat immediately with one of the organic acid-based or thymol-based products: ApiLife Var, HopGuard, Formic Pro, oxalic acid or something similar.

  • Hi Rusty

    I have an oxalic vaporizer. would you treat one time or more than once. Or base that on the amount of mites after treatment. Thanks Linda

    • Linda,

      It depends on how much brood you have. If there isn’t much, once might work. If you have lots of brood, you may have to do it more than once.

  • Hi Rusty, love your site. New beekeeper but I am scientist/engineer and have studied as much as I can to keep them alive. Live in colder New Hampshire, started with good nuc in May. Now I have 2 regular deeps full for the winter plus a medium super they are still laying honey in with our fall nectar run.

    As for mite treatment, I became excited with OA vapor through a mosquito fogger. Easy to do. I gave three rapid treatments in mid to late August 5 days apart to make sure I rotate through the brood cycle. I gave another prophylactic treatment in mid September and last week Oct 1st. After the last treatment I put down a sticky board for 7 days and pulled it out this morning and counted approx. 500 mites (more centered around the middle frames, less on the outside).

    Question: Is this good to see this many dead? Or could it mean that my count was still too high? I’m guessing I should do an alcohol wash but been little scared to screw it up and lose my queen! Probably just gotta jump in and do it.

    NH last year only had 42% survival. Moisture, robbing, nosema, varroa, extreme cold, starvation (not feeding them supplement) are all the major causes. I have moisture/cold problem solved with heater/insulation. Also gonna feed them right on through winter given I will control slightly above freezing. Destroyed all nearby robbers. No sign of nosema plus I feed them good supplements. The last issue is varroa, and I’m just unsure whether I’ve done my job.

    Would love to hear your thoughts on all the above. Thanks so much in advance.

    • Eric,

      You found 500 mites following treatments in August, September, and October? Something is seriously amiss. I agree that you need to count in a more reliable way. If you are uncomfortable with an alcohol wash, do a sugar roll. It is not as accurate as alcohol but much more accurate than a sticky board. Once you have a better count, you need to treat again. Don’t use the same method because it appears not to be working.

  • I’m sorry I just gave 3 consecutive treatments in August (still a lot of brood so the vapor treatment may not be as effective) and then 1 treatment about a week ago in late September. I put the sticky board down after this immediately after this last treatment and left it for a week so I could see how many were killed. I counted 500 mites on the sticky board. I’m assuming this was the effective “kill” rate. My thought is that now that brood is low this should be a high percentage kill (>95%), so is 500 mites a realistic number? There is a very high population still in the hive, probably greater 10-20 thousand so I thought 500 would be 1-3% which is maybe normal?

    But you have convinced me enough that I have to do a good count. I will now do an alcohol wash.

    Thanks. I love your site

    • Eric,

      The only way to get a good estimate is to do the alcohol wash. Otherwise, you are just guessing.

  • Hi Rusty,

    I’ve a simple question to which I have yet to find an answer. When mite counting , is it just the dark mature females or should the occasional lighter deutonymphs and males be included?

    Thanks in anticipation of your answer


    • Asked and answered. Honestly, screened bottom boards don’t kill anything, they merely act as filters.