Monitoring for Varroa Mites: Alcohol Wash Method

by | Oct 18, 2023 | ProTips, Seasonal Checklists

Step-by-step instructions for how to complete an alcohol wash to check your hive for varroa mites.

“An ounce of prevention is worth a pound of cure.”

We wholeheartedly agree with this expression—especially when it comes to monitoring for varroa mites. Yes… mite checks can be tedious and annoying. BUT they do help inform your treatment decisions and record treatment efficacy so you can avoid bigger problems down the road. Although tempting, don’t skip that post-treatment check! Those are handy to find apiaries that need follow-up mite treatment. A late-season treatment is better than no treatment.

When to Do Your Mite Checks (Hint: before and after treatment!)

In order to know if your treatment has worked, you will need to capture mite levels BEFORE you begin treatment and afterwards. This provides essential information of your starting point for comparison later. Your post-treatment monitoring should be done 21 days after treatment ends. The before and after mite levels can be compared to assess the efficacy of your treatment.

Sometimes what seems like a concerning post-treatment infestation level has actually brought your apiary down from extreme infestation. If you did pre-treatment checks but your numbers still seem off, investigate your treatment method. Varroa mites can develop acaricide resistance with repeated or over/under-exposure to chemical treatments. Consider rotating treatment methods or switching to formic acid, which has been used for over 30 years without any known resistance.

 

Mite Monitoring: Alcohol Wash

Our preferred method is an alcohol wash. It’s simple, effective, and only requires a few extra pieces of equipment. We put together a quick refresher on how to complete one:

 

1. Get your supplies ready

  • ½ cup measuring cup
  • Tub or basin
  • Varroa mite counter jar – you can buy a double jar shaker with mesh at your local beekeeping supply store or make your own
  • Alcohol – 95% ethyl alcohol is a good choice, but windshield washer fluid is a low-cost alternative that works just fine
  • Pen and paper/notebook to record your results
  • Funnel (optional)

 

2. Find an ideal frame

Pick a frame with older larvae (just before capping) for your sample. Be sure to find your queen and exclude her, or check the frame very thoroughly to ensure she is not there.

 

 

 

3. Shake your frame

Place your basin in front of your colony entrance and use 1-2 firm shakes get bees off your selected frame and into the bin. Set the sample aside and put your hive back together.

Note: No need to rush here, those bees aren’t going anywhere fast. The field bees will fly away, but the nurse bees (which we are targeting for the sample) should stay put for now.

 

4. Setup to scoop

Ensure your mite counter jar is nearby and filled with 50-100ml (2-3oz) of alcohol. Put your funnel into the jar, if using. Grab your ½ cup measuring cup. If you didn’t exclude your queen, check one last time in the basin for her. Take the bin and tap one corner on the ground to knock your bees into a pile.

 

 

 

5. Scoop bee sample

Use your ½ cup measuring cup to scoop bees into the jar with alcohol and put the lid on. Add the left-over sample bees back into the hive.

 

 

 

6. Swirl your sample

Swish or swirl the jar constantly for 2-3 minutes to loosen mites from the bees. Tip it over to strain the liquid (and mites) from the bees, lightly shaking as you go to dislodge any stubborn mites and take a look. Holding your jar up to the light can help to count the mites you’ve washed off the bee sample. Record your results for each hive you check.

Note: The jars seen here are for the lab version of this task, which don’t include double jar/mesh. We take the whole sample back to NOD’s research lab and count the number of bees and mites in each sample for a more accurate calculation.

 

7. Do the math

A ½ cup is approximately 300 bees. The typical threshold to prompt treatment is 1-3% infestation, which would be about 3-9 mites in our sample of 300.

[# of Mites Counted]  ÷  300  = [your infestation level as a decimal]
Multiply that decimal by 100 to get infestation level as a percentage.

Example: We count 6 mites in the picture shown.

6  ÷  300  = 0.02
0.02 X 100 = 2% infestation level

It’s important to know what the treatment recommendations are for your region and time of year. You can look this up by your state or province, or contact your local bee inspector or association to find out.

 

Watch a Tutorial Video

Looking for more info on how to complete an alcohol wash to check your apiaries for varroa mites? The University of Guelph Honey Bee Research Centre has put together a helpful instructional video on Varroa Mite Monitoring – Alcohol Wash.

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