Variable Efficacy of Mite Treatments?

Drone bee with cocoon stuck on eye and worker with varroa mite present.

Drone bee with cocoon stuck on eye and worker with varroa mite present.

Variable efficacy of mite treatments has been a constant battle for beekeepers in the past 28 years. However, there are some things we can do in the colony to increase a treatment’s efficacy. Many treatments available to beekeepers are spread through the hive by the bees and also by the bees fanning and ventilating the hive. This ventilation is a crucial part of the hive as a whole since pheromones are spread through the hive via ventilation and traffic from worker, queen and drone bees.

Drone pupa with varroa mite present.

Drone pupa with varroa mite present.

Through my experience, and especially over the past 8 years, I have noticed many different types of beekeepers: there are those who are diligent in scraping burr comb, there are beekeepers that scrape the hives only a few times a year, and those who choose not to scrape at all. After seeing this trend year after year the thought came to me, how does bur comb effect mite treatment efficacy? This question is still not answered scientifically but I do feel that contributes to the inconsistencies within apiaries treated in the same way. These varied results are especially noticed with using fumigation type treatments, one example would be formic acid or Mite Away Quick Strips (MAQS). There have not been any studies that I found on evaluating the treatments with or without burr comb but I think this something that needs to be and could be evaluated.

Varroa Mite on deformed wing virus bee.

Varroa Mite on deformed wing virus bee.

Scraping burr comb down 3-5 days prior to treatments could affect the efficacy of the treatment. I would not recommend scraping bur comb and treating within the same day due to hive stress from having to clean, repair and reconstruct ventilation pathways. During time of treatment, it may also be beneficial to feed the colonies some protein supplement, this will give the bees some extra food to cope with stress and also draw them closer to the treatment. Feeding sugar syrup is another method you can use to give the bees some help with coping with the treatment stress, but a fondant patty may be better because it will draw bees towards the treatment.

Worker bees with Deformed Wing Virus (DWV).

Worker bees with Deformed Wing Virus (DWV).

I have been scraping my hives since I started beekeeping because that was the way I learned, but only after many years have I realized that this habit may contribute to successful overwintering and more consistent mite treatments. I hope this information was useful and I would appreciate any stories or information on how scraping burr comb has increased or decreased efficacy of mite treatments.

Queen Bee

Queen Bee

Written By: Rob Snyder

Rob Snyder has written 67 post in this blog.

I currently work out of the Butte County Cooperative Extension in Oroville, CA as a Crop Protection Agent. I received my B.S. in biology from Delaware Valley College, PA. There I attained a majority of my entomological knowledge from Dr. Chris Tipping and Dr. Robert Berthold. After graduation, I was an apiary inspector for 2 years at the Department of Agriculture in Pennsylvania. In my third year there, I still inspected some colonies but I mainly focused on The Pennsylvania Native Bee Survey (PANBS) where I pinned, labeled, entered data and identified native bees to genus species. Leo Donavall assisted me in learning the basics on positive Identifications of the native bees. Around the same time I began working on coordinating kit construction and distribution for the APHIS National Honey Bee Survey. I was also fortunate to conduct many of these surveys with fellow co-worker Mike Andree and Nathan Rice of USDA/ARS throughout California. All of these experiences have led me to where I am today, working to assist beekeepers in maintaining genetic diverse colonies resistant to parasites while reducing the use of chemical treatments in colonies. The BIP Diagnostic Lab at the University of MD is in an integral part of this process by generating reports in which we can track change and report to beekeepers vital information in a timely manner which may influence their treatment decisions.


22 Responses to “Variable Efficacy of Mite Treatments?”

  1. 3 B APIARY

    Could the scrapping of burr comb also be releasing propolis and properties/chemicals that could be protective?

  2. David Wood

    Seeing bees with DWV, reminded me that they would carry the virus, and it they were in the hive long enough to become nurse bees (they are usually ejected by other bees in a couple of days) they would spread the virus to larvae.

  3. Meg

    Just from the title of this blog post it reminds me of a mite treatment that is not usually discussed or that I have yet found documentation of in any beekeeping books (U.S./U.K.) but have used and know other beekeepers use.

    Mites are drawn to drone brood and lay eggs in the brood. It is possible to put in 1 frame of larger cell wax foundation in a deep frame, marking the top of the frame so it’s easily found again. Since the cells are larger the bees are draw out for the drone comb and thus the queen will lay drones. Since drones hatch out at 24 days, the beekeeper can simply come out before the 24 day mark and cut out the drone brood.

    Doing this twice will cut the mite load down 90% according to the University of Minnesota when asked at the Beekeeping in Northern Climates class.

    If there is any known documentation on this, I would love to know about it.

  4. Don Coats, DVM

    Hi Rob, Based on my clinical background I have grown concerned about the various opinions, rarely updated, regarding Nosema and its effect, actual or imagined on bee health. Are you aware of any current studies reported or in process regarding this organism?

  5. Rob Snyder

    Often there is not much propolis on the top bars of frames (bottom box), Propolis may be more present in the top box under the lid, but I dont think its doing much for hive when you scrape it. Increasing ventilation from scaping however will assist the colony to create better airflow through the hive.

  6. Rob Snyder

    Culling drone brood does help but I don’t think it will cut the load down to 90%, especially going into the fall. Also, when you cull drone you are setting the colony back and will decrease honey yeilds. I used to drone trap for a number of years pulling the frames every 2 weeks or when they were filled out, but once I stopped doing this method the colonies were more productive and made 1-2 mediums of honey more.

  7. Carley

    Hi Meg, We cut drone brood out of our hives during Summer. We also sample it to get an idea of varroa load in the hive. Have you seen any data on how many varroa it is okay to have in drone comb? Since the drone comb captures the varroa I assume the data would be different and quite possibly higher than say a sugar count of varroa on adult bees. Carley

  8. Megan

    Hi Carley-
    The best information I have seen is from the U of M, they are looking at how many mites equate the percentage of mites in a honey bee hive. I attached a poster

  9. Meg

    Sorry my message got cut off; The best information is attached-it’s a poster of how a sugar roll is done, the last two slides point out the # of mites in a sugar roll test is the percentage of investation in a hive of mites. Typically it is said that a “treatment” (either chemical, mechanical or other) needs to happen at
    3-5%, which seems low, but treating early and keeping mite populations low in hives is important.

    Also note the population rise of mites corresponds with the build up in the hives, but the peak of mite population is AFTER the honey bee population is starting to wind down (either with lack of forage or starting to slow down for fall-depending upon the region you are in)

    Hope that answers you’re question.

  10. Carley

    Thank you. Looks good but I am looking for how many mites is acceptable as a percentage in the drone brood. I don’t know if anyone has produced that data yet.

  11. Carley

    Good information on when the peak is. Thank you. I am looking for acceptable varroa percentage in drone brood that we are cutting off. Thanks again.

  12. Meg

    You’re welcome. It would be the same as the sugar roll test idea, 1/4 cup of bees is ~300 bees (younger nurse bees on a mix of open/sealed brood) and the count is after shaking them with sugar to release the mites from the bees. With drone brood I guess you could open up 100 cells and see what you can count. Remember that the mites in the drone combs will be a adult female (visable) and much smaller eggs/mites (very small and not invisiable but hard to see in the comb unless you open it up really well). This is why the sugar roll test to nock off adult mites (visiable to the eye) is a much easier count/understanding of investation rate.