This method consists of immersing a sample of bees into a container of alcohol to detach the phoretic mites so they can be counted.
It is the most consistent in terms of delivering accurate results, and is commonly practiced by beekeepers, apiary inspectors, and scientists
throughout North America.
How to perform an alcohol wash?
Required material (not included): Rubbing alcohol, or cleaning alcohol, or diluted ethanol, or windshield washer fluid containing alcohol.
Fill half of the transparent container of the Varroa EasyCheck with the liquid.
Gently shake the Varroa EasyCheck® for 1 minute.
Make rotations and side movements to help the mites pass through the holes.
Avoid turning the Varroa EasyCheck upside-down, as it might block the mites inside the lid.
You can then filter the liquid into a very fine sieve and re-use it up to 10 times for new hive counts.
Collect a sample of 200 or 300 bees with the white basket, preferably from a frame of capped brood (make sure the queen is not in the sample). The lines for 200 and 300 bees are indicated inside the basket.
Put the basket back into the transparent bowl and quickly close with the lid, to prevent the bees from escaping.
Count the mites directly by looking at the bottom of the transparent container.
Depending on if you took 200 or 300 bees divide the number of counted mites by 2 or 3 to get your infestation rate (%). To interpret the results, please consult our Varroa Guide and/or your local thresholds.
Collecting a sample of bees: which impact on the colony?
The “sacrifice” of a bee sample may discourage some beekeepers from monitoring their colonies. But you need to think of the sampling like you would a blood test: you take a sample of blood to guide a diagnosis, but it is such a small amount that it has no consequence on your overall health or well-being. The sacrifice of 200 to 300 bees is similar:
Sampling will give information that will improve the health management of the rest of the colony and the entire apiary. The alcohol wash method, which gives accurate results, but does sacrifice bees, will eventually avoid colony mortality.
The damage to the monitored colonies should be put in perspective, because a limited loss of bees in the season has little consequence in a colony which generally contains between 20,000 and 35,000 individuals, and whose queen can lay more than 2,000 eggs per day (at the peak of laying). The sample taken usually represents less than one percent of the overall population of the hive, and the bees will be quickly replaced.