Varroa mites and the viruses they spread are the most serious challenge faced by beekeepers today. Determination of mite levels is very critical because it allows the beekeeper to know when control measures are necessary and also determine the effectiveness of treatments and control measures already applied.

There are three methods commonly used to determine mite levels in colonies. What method you choose will depend on your individual situation and preference. The important point is that you need to monitor mite levels so that measures can be taken to keep mite levels low enough so that colonies remain healthy.

Alcohol wash

Varroa Easy Check

The alcohol wash uses alcohol or windshield wiper fluid to separate mites from the sample of bees. The disadvantage is that the sample of 300 bees is sacrificed for the test. The advantage is that this is the most accurate and consistent method to accurately determine mite levels. Keep in mind that although 300 bees seems like a large number, the queen typically produces between 1,000 and 1,500 eggs per day and the loss of 300 bees has no harmful consequence. We prefer the Varroa EasyCheck to do the alcohol wash. Here are the basic steps:

  1. Place alcohol or non-foaming windshield washer fluid into the Easy check container. Add enough fluid so that it is above the bottom of the inner perforated cylinder.

  2. Locate the queen and isolate her so that she is not included in the sample.

  3. Select a frame of bees from the brood nest. Scoop a 300 bee sample by gently sliding the inner filter cup down the frame. Continue until the bee level is the even with the upper line. Alternately you can shake the frame into a container such as a plastic dishpan and scoop the sample from the pan. You can use a one-half cup measure or the inner filter cup to obtain your 300 bee sample.

  4. Place the filter cup into the outer container and put on the cap. Shake once to wet the bees and then add fluid up to the upper line on the outer container.

  5. Shake container gently for 60 seconds.

  6. Hold the container up to the light and count the mites.

  7. Divide count by 3 to get a percentage (e.g. 15 mites per 300 bees = 5 per 100, or 5%).

  8. Watch this short YouTube video on how to perform the test using the Varroa EasyCheck.


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Sugar Roll

Dumping Bees Back Into Hive

The sugar roll technique is similar to the alcohol wash in that it measures the mites in a 300 bee sample. Unlike the alcohol wash the bees are not sacrificed. A disadvantage is that all of the mites are not recovered from the sample and results are more variable than with the alcohol wash. Here are the steps for performing a sugar roll.

    1. Locate the queen and isolate her so that she is not included in the sample.

    2. Select a frame of bees from the brood nest. Shake the frame into a container such as a plastic dishpan and scoop the sample from the pan using a one-half cup measure to obtain your 300 bee sample.

    3. Pour bee sample into a wide mouth Mason jar and cap with lid equipped with one-eighth inch hardware cloth screen.

    4. Add 2 tablespoons full of powdered sugar through the screened lid. Gently roll the jar until bees are well coated with powdered sugar. Leave the sample jar in the shade for two minutes to allow mites to separate from bees.

    5. Invert the container and shake vigorously, shaking the sugar into a white container or paper plate. Shake vigorously for one minute so that all sugar and mites are removed. You can use a white dishpan both to shake your frame and to shake sugar and mites from the sample jar.

    6. Mist water into the container so that sugar is dissolved and mites become apparent.

    7. Count mites. Divide count by 3 to get a percentage (e.g. 15 mites per 300 bees = 5 per 100, or 5%).


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Natural Mite Drop

Another method to use for determining mite levels is the natural mite drop. A screened bottom board or varroa screen is used to count the number of mites that fall from the colony in a 24 hour period. One advantage is that the hive does not need to be opened to perform the test. One simply counts the number of mites on the tray in one 24 hour period. The test can easily be repeated at regular intervals to determine whether the mite count is increasing.

Screened bottom board & tray use for 24 hour mite drop test

The screened bottom board is used in place of a standard reversible bottom board. The tray slides in from the back. There is no need to use a bottom board unless you prefer to use a hard plastic tray for varroa monitoring.

Screen bottom board for mite test

24 Hour Varroa Mite Monitoring

  1. Wipe the tray clean and then coat with a small amount of vegetable oil or petroleum jelly

  2. From the back of the hive, slide the tray in beneath the screened bottom board. Do not examine the colony during the 24 hour mite drop period. We are measuring natural mite drop which will be altered if the colony is examined.

  3. Remove tray after 24 hour period and count the mites. Mites can be very difficult to see and identify. We recommend using a magnifying glass and a bright light source. They are reddish-brown with a smooth hard outer shell. See picture below:

    Mite Count

  4. Once you have completed your mite count, record it in your bee journal. We suggest repeating the check every 2 weeks so that trends can be seen. Interpret the mite results using recommended thresholds, below.

Interpreting mite count numbers

Interpreting mite counts is an important step, and recommendations vary based on the method used to count mites and the time of year, as well as other factors. Betterbee is comfortable recommending mite treatment thresholds suggested by the Ontario Tech Transfer Team. See chart below.

Ontario Tech Transfer Team Recommendations

Treat when your mite count exceeds these numbers:

Monitoring Method

Number of Varroa Mites in May

Number of Varroa Mites in August

Sugar Roll

1 mite/100 bees

2 mites/100 bees

Alcohol Wash

2 mites/100 bees

3 mites/100 bees

Monitoring Tray

9 mites/24 hr drop

12 mites/24 hr drop


There are many options for treating mites. Visit our Pest Management & Medications page for more information on the various treatment options.

 

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