Varroa Mites in Beekeeping: Effective Testing and Treatment Methods for Success

Varroa mites are considered the leading cause of honey bee mortality worldwide. This may sound alarming, but it's a sobering reality, especially with recent reports showing honey bee colony losses exceeding 50% in some regions.

As beekeepers, we are responsible for utilizing the tools and strategies available in our industry to combat these pests. Our ultimate goal is to reduce the impact of Varroa mites on our colonies and ensure their health and productivity in the long run.

Understanding the Ideal Mite Load

Your objective is to maintain a Varroa mite load of less than 2%, which equates to no more than 6 mites per 300 bees. The only way to accurately assess this is through regular testing. One of the most intimidating aspects of beekeeping for newcomers is the process of conducting a Varroa mite test. This often leads to premature treatments without proper testing—something many beekeepers are guilty of. However, there are accessible options for testing that can suit different comfort levels.

Testing Methods: From Most to Least Accurate

Here are the most common testing methods, ranked in order of accuracy:

1.      Alcohol wash (< 6 mites per 300 bees)

2.      Powdered sugar shake (< 6 mites per 300 bees)

3.      Sticky board test (< 9 mites over a 24-hour period)

Alcohol Wash: The Gold Standard

The alcohol wash is the most accurate method for testing for Varroa mite infestation. The Varroa EasyCheck system offers a convenient, ready-made jar with measurement lines for precision. While you can perform this test using a regular quart jar, the EasyCheck system's basket makes the process much easier. For an added protection against killing a queen in mite testing you can use the Queen Excluder for EasyCheck mite wash. 

Steps for Performing the Alcohol Wash Test:

1.      Remove a frame from the brood box that is covered with bees and open brood. Ensure the queen is not on the frame.

2.      Shake the bees gently onto a sheet of newspaper or a honey bee sampling and grafting tray.

3.      Quickly transfer around 300 bees (approximately half a cup) into the jar by folding and shaking the newspaper, creating a slide to move the bees into the container. If using the honey bee sampling tray, this step is much easier.

4.      Add about 2 cups of 90% rubbing alcohol or a Dawn dish soap solution (2 Tbsp. per gallon of water) into the jar with the bees. Gently shake and swirl the jar for about a minute.

5.      Hold the jar up and look at the bottom to count the mites as they settle.

6.      If you count more than six mites, it's time to treat your colony. If fewer than six mites are observed, retest in about four weeks to monitor the mite population.

Sugar Roll Test Using the Varroa EasyCheck

The powdered sugar shake method is popular because it doesn’t harm the bees, but it is generally less accurate than the alcohol wash. If you don’t have an EasyCheck, you can use a pint-sized canning jar with #8 hardware cloth as the lid.

Steps for Performing the Powdered Sugar Shake Test:

1.      Follow steps 1 through 4 from the alcohol wash procedure.

2.      Add about 3 tablespoons of powdered sugar to the jar.

3.      Shake the bees into the container. If you are using a Varroa EasyCheck, remove the basket before adding in the bees. Once the bees are in, invert the basket to trap the bees inside. Then screw the yellow lid on.

4.      Shake the bees in the jar for about 30 seconds to coat them thoroughly with sugar.

5.      Let the container sit for two to five minutes.

6.      Shake the bees again for another 30 seconds.

7.      Turn the container upside down and shake all the powdered sugar out through the inverted basket onto a flat surface. Tip: Shaking the powdered sugar out over a plate with a small amount of water on it will dissolve the sugar, making it easier to see the mites. 

8.      Count the mites.

9.      A treatment threshold of more than 6 mites per 300 bees is recommended. If fewer are counted, retest in about four weeks. Keep in mind that this method may not remove all the mites for accurate testing, so even counting four to five mites should prompt you to consider treatment.

10.   Return the bees to the hive by shaking them back inside or in front of the entrance.

Sticky Board Test: A Simpler, Less Accurate Method

While the sticky board test is the simplest, it’s also the least accurate. It can provide a general indication of mite presence, but it won’t give you a precise mite count.

For Screen Bottom Boards:

1.      Place the sticky board under the screen bottom board and above the tray that closes it off. If you don’t have a tray, make sure the sticky board is inaccessible to the bees.

2.      After 24 hours, count the mites on the sticky board.

3.      If you see more than nine mites, treatment is necessary.

For Solid Bottom Boards:

1.      Place the Varroa Screened sticky board inside the hive on top of the solid bottom board.

2.      After 24 hours, count the mites.

3.      If there are more than nine mites, treatment is needed.

Important: Check the board exactly 24 hours after placing it. Leaving it longer will distort the results.

Varroa Mite Treatments

How one addresses Varroa mites remains a controversial topic within the beekeeping community. The most important thing is to choose a treatment method that aligns with your approach to beekeeping. And most importantly, always test before you treat. Once you’ve confirmed that treatment is needed, you have two primary options: synthetic chemicals and natural compounds. While mechanical and cultural methods can also help manage mite populations, they should be used in conjunction with chemical or natural treatments for best results.

Most synthetic chemical and natural compound Varroa treatments tout an efficacy rate of over 95%, with some natural compounds claiming as high as 99%. The difference is mainly in the overall colony losses per year. There is documented evidence that the overall losses are significantly lower with the more aggressive treatments such as Apivar (upwards of 47% improvement over 31% with natural compounds). There is also evidence that the likelihood of queen and colony degradation is lower with these chemicals as opposed to their natural compound counterparts. 

Not to shortchange the natural compound benefits. They do rank in the higher efficacy rate of 95–99% when controlling Varroa mites and are considered organic by legal standards for the industry. Most of these products use a fumigant-distribution system; therefore, the bees aren’t very fond of them. Bearding and absconding have been documented as real issues while using these products but not so much as to outweigh the benefits to some. Queen and brood damage have also been noted but, again, not beyond the scope of benefits outweighing risks.

Important Considerations for Treatment

• Always carefully read the product instructions, especially regarding the recommended population stage and temperature ranges. For instance, most treatments can be applied only during certain population stages (increase, peak, decrease, or dormant), and applying them at the wrong temperature can cause stress or even lead to a colony absconding.
• It’s highly recommended to use mechanical and cultural methods alongside chemical or natural treatments. These additional practices will help ensure that your bees are as healthy as possible while minimizing the need for chemicals.

Beekeeping Checklist:

• Pay attention to population stage and temperature when selecting a treatment.
• Requeen your hives every year to ensure healthy, productive colonies.
• Create natural brood breaks by making splits when feasible.
• Always test before treating and follow up with a test after treatment to ensure efficacy.

By staying diligent in your testing and treatment practices, you can give your bees the best chance for success in managing Varroa mites and sustaining a thriving, healthy colony.