varroa mites

The mites are the same old mites

Each time I think I’ve written my very last post on varroa, something else comes up. This time, it was a question about how to treat for mites now that we know mites eat fat bodies instead of hemolymph.

Based on what I’ve read, I would say that if you are following current best practices for controlling varroa, you shouldn’t have to make any changes in your mite management protocol. Current practices were developed based on what works best, regardless of what the mite was eating. Someday that may change, especially if someone develops a different way to treat based on the new information. But for now, it doesn’t change much in the field.

The mites are the same old mites—only our understanding of them has changed. However, the new information does help to explain many of the things we see in a colony overrun by mites, and it helps explain why things go downhill in a such a hurry.

The discovery

Dr. Samuel Ramsey discovered that mites do not eat hemolymph alone. Instead, they seek out fat bodies which are found in the honey bee abdomen. Because fat bodies are essentially bathed in hemolymph, it is easy to see why earlier researchers missed the connection.

Ramsey also learned that varroa mites found riding around on adults—especially those on the ventral side of the abdomen—are actually biting into the bee and eating. Like diners riding the dinner train, these mites are feasting while they get ferried about the hive. Not good news.

Up until this discovery, the theory was that the mites were parasitic on the developing pupa, entering the cell just before capping and then feeding beneath the capped cell. We also believed that after the bee emerged, mites had a phoretic stage, and it was these phoretic mites that we occasionally saw in the hive or riding a bee.

But phoresy is a situation in which an organism is riding on a host but not acting as a parasite. This new information shows us that the mites are not phoretic when they are riding around on adults, but rather they are parasitic in that stage as well. Basically, we now know the mites are feeding throughout their lives: under the cell cap they feed on pupae and loose in the hive they feed on adults.

Treating for mites

For a number of years, the standard advice has been to treat your colony for mites before the winter bees develop. For most of North America, this means treating in August such that the treatments are completed by the end of the month.

The winter bees, which emerge beginning in September or October, are the long-lived bees that tend the colony until spring. In healthy bees, the fat bodies act as protein reserves that allow spring brood to be raised even in the absence of sufficient pollen. If these bees are not healthy and strong they won’t last until spring, or they won’t have enough protein reserves to feed the young.

To keep the winter bees healthy and prevent infection by virus, the colony must be virtually free of varroa as it goes into fall. If treatment is delayed until after the winter bees are born, the treatment will do little good. A treatment in November, for example, will kill the mites but it won’t help the bees that are already infected with virus. Often, a colony treated late will collapse as quickly as one not treated at all.

Before Ramsey’s findings, we believed the winter bees were weakened primarily by infection from virus. This is probably still true, but now we know that honey bee fat reserves are also compromised by the mites, a situation that shortens their lives or makes them incapable of feeding brood even when they are virus free.

Monitor before you treat

As for a treatment schedule in North America, August is still the most important time to go after the mites. Depending on your local situation, you may need to treat more frequently, but the late summer treatment is the most critical, especially in terms of timing.

In any case, monitoring for mites is vital. You shouldn’t treat if you don’t need to, and monitoring mites with an alcohol wash (preferred) or sugar roll will give you the information you need. After treatment, you should count again to assure yourself that the treatment worked. If you are a treatment-free beekeeper and find a collapsing colony, consider destroying the colony before it delivers its mite load to your other colonies, neighboring colonies, or feral stock.

Honey Bee Suite

Don't be fooled by appearances. Mites like to dig between the sternal segments, which are found on the underside of the abdomen. Once they grasp the abdomen, they can begin to feed. A mite feeding on an adult bee is not easy to see.

Don’t be fooled by appearances. Mites like to dig between the sternal segments, which are found on the underside of the abdomen. Once they grasp the abdomen, they can begin to feed. A mite feeding on an adult bee is not easy to see.


  • It’s my understand that the sugar roll isn’t effective now and only the alcohol wash gives a good indication of mite levels because the mites embed them selves in the folds on the ventral side and the sugar roll doesn’t dislodge them. Have you read/heard this?

  • Good morning Rusty – great post; I learn something new every time. I didn’t establish my new hive until early July, and the nuc had been treated before I got it. Thus, all through July and into August my mite count was zero or close to; it wasn’t until mid-October I started getting numbers so that’s when I treated, into early November. Based on your post above is this likely to impact my colony? Will I need to treat again (although we really don’t have days warm enough where I can open the hive and do a sugar shake) and should I do it over the winter or first thing when it warms up? Thanks!

    • Hi Stosh. Good to hear from you.

      Since you were monitoring, and you found low mite counts in August, there was no reason to treat. Good job. But lots of colony collapses occur in fall, so you probably picked up mite-laden bees from somewhere else, which spiked your mite count.

      Treating in November is usually quite effective because brood nests are small or non-existent. I hate to give advice because every situation is different, but if it were me, I would just leave the colony alone until the weather warms up. Then you can monitor again.

  • An interesting and simple citizen science experiment is to do a sugar roll test and follow it with an alcohol wash using the same bees. The number of mites in the second, alcohol, wash, will show how effective or ineffective the sugar roll was. I do this with one hive every year, and will share the results with anyone who is so interested – I don’t want to influence perceptions by sharing the results prematurely. An interesting question would be – what would one expect the difference to be?

    • Jeremy,

      I don’t know what the difference is, I only know that it is huge. But that’s not the point. Many people simply will not kill bees in alcohol, so they don’t do counts at all. By using the inferior method, they do not kill bees, but they still get enough information to reach a treat/no treat decision. I would rather see beekeepers do something rather than nothing.

  • The amount of damage that the “phoretic” mites do to a colony was sadly illustrated this fall… I was mentoring a beek whose hive whose mite counts were 6 or 9 per 300 bees (via alcohol wash) in August. The hive was treated once soon after with OAV. By the time I got back in early Dec, there were a handful of bees on the combs, lots of dead bees on the bottom board, and 60 mites per 300 bees.

    You don’t get that many mites in a couple of months – unless many were imported. There is a beekeeper not far away with several hives… so this was a mite bomb, where the larvae were likely not even “sucked on” at all. The adults were shredded solely. This is triggering a big management change for me- I will be recommending Apivar in Sept now, not to save the winter bees but to protect the hive from imported mite bombs. This is a separate mission from earlier mite control in the year, which is intended (and hopefully will!) save the winter bees.

    If the mentee had been checking his mite levels monthly, we would have discovered the spike sooner. So that really highlights the importance of monitoring. Just kicking myself that I didn’t anticipate this better. Well, next time…

    • Trish,

      That is a sad story, but it’s also a common one. When local colonies begin collapsing in the fall, once-healthy colonies will get inundated. People not treating, or treating at the wrong time, can devastate a large area.

  • I do not know if I’m asking in the correct place, please move if needed. I am asking a question that I have not able to find the answer.

    Can anyone tell me if varroa are active in the northern winters? I live in Michigan. The reason I am asking is because I have screen bottom cover boards installed which I check on a regular bases and have not seen any mite drop.

    This fall, October, I treated with oxalic acid vaporization (5 treatments). Shouldn’t I see some drop on the boards, even if there were only 10 mites left?

    I have 6 hives and they are doing great! The last two days, January 4th & 5th 2019, have been 45 degrees with no wind and full sun; so they have been able to go outside. They were out en masse! Yellow snow everywhere.

    Thank you anyone, for an answer.


    • Robert,

      Varroa mites overwinter in the hive along with the bees. However, as long as there is no honey bee brood, the varroa mites have no way to reproduce. Their numbers will stay constant until some honey bee brood provides them a place to reproduce.

      So if you killed most of the mites, and then you went into a period with little or no honey bee brood (which you most likely did in Michigan), then you would have very few mites during the winter. As the spring gets closer, and brood rearing resumes, you are apt to see more.

  • Rusty,

    Have you reviewed the European Studies and US 1997 SARE study which also shows that a controlled temperature will terminate the mite under the capped brood with no harm to the bees, larvae, or eggs?

    I have copies I would be willing to share and now there are American & European Thermal Treatment products available.

    Lynn W.

  • Point taken, Rusty, esp, the something rather than nothing idea. Yet I wonder if we’re dealing with a scientific v an anecdotal situation? In my simple experiments, there is very little difference between the results of a sugar roll and an alcohol wash in terms of mite counts, with the proviso that the sugar roll is done correctly. It would be intriguing if some of your readers were willing to do the same comparative tests, and provide some data. Also, observation has led me to believe that the sugar roll test, if it does not kill bees, severely damages their wings to the extent that if they are foragers, they can no longer fly.

  • Not sure where to pose this question. I’m assuming our missing bees are gone due to mites. We are first year bee keepers with just one hive. When we started out, we bought an existing hive last spring that did not seem very strong after a couple months. Our bee supplier brought out a new hive that seemed much stronger. It had a healthy 1st year queen, quite a bit of honey already produced, and throughout the season it really seemed to prosper.
    We had questions about mites and the screened bottom board that was missing the tray but never got return calls. Thus, we just left the bees winter over and to our surprise, they had vanished when we open the hive on March 30th. This has really pushed me to study more and more, especially about mites. But, we are not sure what to do!? Are the mites gone with the bees? And secondly, if so, should we try to restore the hive with new bees, leaving the existing comb and honey in place in the upper hive body? Now that I understand the screened bottom board, I plan on using it and sticky paper to monitor the new bees and mites.


    • Richard,

      It certainly sounds like a mite problem. And no, the mites are never gone. Even if none are in the hive, they soon arrive, picked up by bees on flowers, or flying in on other bees that enter your hive from an infected colony. It doesn’t take long for a clean colony to become infected.

      If the bees did not die of a brood disease (and it sounds like they didn’t) you can easily reuse both the brood combs and the honey.

    • Richard,

      It certainly sounds like a mite problem. And no, the mites are never gone. Even if none are in the hive, they soon arrive, picked up by bees on flowers, or flying in on other bees that enter your hive from an infected colony. It doesn’t take long for a clean colony to become infected.

      If the bees did not die of a brood disease (and it sounds like they didn’t) you can easily reuse both the brood combs and the honey.

  • Hi,
    we are beekeepers from Lithuania. We are fighting mite problem as well. We usually treat bees with special substances like formic acid. What are your choices for that problem? Since it is possibility that varroa might get used to treatment, we try to change different medications.

  • I have been looking into how long the DWV lives on hive surfaces and have not been able to find a suitable answer. I lost 75% of my apiary last year and I noticed that DMV was present. I am trying to rebuild my loses using the old equipment (boxes and built up frames with empty cells) and wondered if the virus could still be viable on the surfaces. If so I then will replace everything with new frames and boxes.

    • Rolland,

      The way I understand it, the deformed wing virus cannot live long outside of its host (Apis) or its vector (Varroa). Like many human viruses, it must be in a living cell to survive. If there is a period of potential transmission outside the cell, it would likely be on the order of hours, not days or weeks.

      I can’t find where I read this (although now I’m on a mission to find it), so for the moment, I can’t give you that information. However, I do know beekeepers consider beehives that collapsed due to varroa (and DWV) to be perfectly safe to use without any disinfection protocol. From my own experience, I never had a problem. I’ve reused varroa deadouts for new colonies that ultimately survived many years. I’ve also had swarms move into varroa deadouts without any noticeable problem. They still get varroa, of course, but when the mites are controlled in the normal way, DWV is manageable.

      Remember that as soon as new mites move in, DWV is coming with them. Also remember that there is some amount of vertical transmission of DWV (queen to offspring) that occurs, although it usually occurs at levels that won’t wipe out a colony.

      Bottom line: No one I know of destroys equipment, boxes or frames or anything else, after a varroa/DWV infection.

Leave a Comment

This site uses Akismet to reduce spam. Learn how your comment data is processed.