Delaware Beekeepers                           Association

Varroa Mite check frequency

  • 15 Dec 2023 3:55 PM
    Message # 13291518

    How often should I be doing a varroa mite check during the year?  How early in the year can I use a treatment that does not harm the queen?

  • 19 Dec 2023 11:02 AM
    Reply # 13292625 on 13292309
    Anonymous wrote:

    Monitoring for Varroa mites is an important part of planning your mite treatments. By monitoring, you know you are treating only as much as you need to. It's a waste of time and money to treat for mites when mite levels are low! In addition, if you wait too long to treat, it may take multiple treatments to bring mite numbers down to an acceptable level. Varroa mites can also develop resistance to certain chemicals. It's important to check mite levels before and after treating, because then you can make sure your mite treatments are working.

    Before I can get into how often to check for mites, I need to explain what I mean by "checking for mites." Simply looking for mites on bees' bodies is not enough. Mites are tiny and hard to see! By the time you're seeing mites on your bees, you are dealing with a severe mite infestation. When I say "checking for mites," I mean using the alcohol wash or powdered sugar method. These methods provide a percent infestation (the number of mites per hundred bees). Having the percent infestation is important, because you can use that number to make decisions. The treatment threshold for Varroa mites is 1 to 3 percent infestation, depending on the season. It is recommended to check for mites using the alcohol wash or powdered sugar method once a month. 

    Mite infestation numbers tend to increase slowly throughout the spring and summer, and then spike in the fall. This is because the colony size increases alongside the mite population. As the colony growth plateaus in the fall, mite counts increase rapidly. As a result, it is recommended to follow a low treatment threshold of 1% infestation in the spring, when mite levels have all season to increase. In the late fall, you can use a treatment threshold as high as 3%, because mite numbers are reaching their peak. 

    For a video on how to check for Varroa mites, click here.

    The second question was about how early you can treat, and how to avoid damaging the queen. The answer is, it is never too early to treat! Oxalic acid (applied by fumigation or dribble methods) is one treatment that is not temperature dependent. That means you can use it in winter and summer. Oxalic acid is also not known to cause queen failure. Thymol (Api Life Var and ApiGuard) and formic acid (Formic Pro) are treatments that can be a bit more likely to affect the queen. However, when used correctly, these are useful tools for managing Varroa. It is important to rotate between miticides with different active ingredients, to prevent mites from developing miticide resistance. 

    For a guide on treatment methods for Varroa mites, click here. 

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