Keeping your mite counts under control requires steadfast monitoring and subsequent treatment as necessary. While mite inspections had a reputation for being tedious, and occasionally inaccurate, the alcohol wash method makes it quick and easy to keep an eye on mite counts.
Alcohol washes are an accurate and fast way to determine the varroa mite infestation rate on a subset of the adult bees within a colony. Test results allow you to compare the infestation rate with published thresholds and make decisions about whether or not treatment is warranted. We use the Varroa EasyCheck and the Varroa Mite Test Bottle to check our bees for mites.
We do alcohol wash tests regularly (monthly is ideal) to monitor colony health throughout the entire bee-working year to make sure mite levels remain below economic thresholds. This helps us plan ahead for treatment opportunities. It’s also a smart idea to do an alcohol wash approximately 10 to 14 days post-treatment to verify that your mite treatment was effective.
Doing alcohol washes regularly will improve your skill in collecting the sample and performing the test accurately. It may seem a bit awkward at first, but with experience, it will become faster and easier; a routine part of your hive management skills.
Because the actionable levels of infestation (e.g. when treatment is needed to protect the colony from harm) are quite low — only 2 or 3 percent — a particular subset of the bees in the colony is chosen to act as surrogates for all the adults in the hives. The bees with the highest infestation rate are the young nurse bees occupied tending the brood. Phoretic-state varroa mites congregate on the bees working near the open brood so that they can easily enter a mature larva’s cell before it is capped.
To maintain the accuracy of the test, it’s important to choose the sampled bees correctly and consistently, both as to the location they are taken from, and the number of bees in the test sample. The methods described below will help you do that.
An alcohol wash uses isopropyl (rubbing) alcohol or non-foaming, winter windshield wiper fluid to separate the mites from the sample of bees. Using a Varroa EasyCheck or Varroa Mite Test Bottle sampler is an accurate method to determine mite levels, and compared to a sugar roll, an alcohol wash is faster because you do not have to return the tested bees to the hive. The disadvantage is that the sample of 300 bees is sacrificed during the test, meaning that some bees die.
Many beekeepers are hesitant to kill the tested bees. Keep in mind that although 300 bees seems like a large number, a queen typically produces between 1,000 and 1,500 eggs per day and the loss of 300 bees has no harmful consequence.
Because testing requires removing bees, which may aggravate them, wear the appropriate protective safety gear — a beekeeping suit or jacket, gloves, and veil. Additionally, to prepare for testing, gather the necessary supplies:
Important Note: Because this test kills all the bees that are tested, it’s important to find your queen and make sure she isn’t among the bees being tested. If you cannot be certain that you will be able to spot your queen, select a frame away from the brood nest and use that one for the test.
Getting the bees into the sampling container is a critical step in achieving test accuracy. A precise, and consistent, sample size (the number of bees actually tested) is the key to getting reliable results, so take some care with this step. There are two common methods that work for gathering bees to sample.
Method one: Set a plastic tub on the ground. Hold the selected frame firmly and give it a sharp downward shake directly over the tub. This will dislodge the bees and drop them, unharmed, into the box. The nurse bees, unlike the foragers and drones, will stay in the box for a short period.
Then, consolidate the bees in the plastic tub by giving one corner a sharp thump on the ground. This will drop all the bees down into that corner of the box, which will allow you to use a half-cup measuring scoop to gather a test sample from the bees in the corner of the box.
Remove the lid of the test bottle, dump the bees into the inner basket, and put the lid back on.
Method two: Or, after finding and isolating the queen, select a frame from the brood nest. Either brush the bees from the frame into the empty basket or slide the basket gently up the frame, scooping the bees so they fall down into it. Continue until the level of bees in the basket reaches the upper line on the cup — this is equivalent to a 300 bee sample. Then, place the cup into the outer container and put the lid on.
After you’ve counted the mites, lift the basket out and discard the bees. Pour the sampling fluid through the strainer to remove the mites and debris. The sampling fluid can usually be reused a few times before it needs to be replaced.
Watch this short YouTube video on how to perform the test using the Varroa EasyCheck test option.
Although some beekeepers will allow a 3 percent infestation rate — 9 mites revealed after the test — at Betterbee, we consider the mite treatment threshold to be 2 percent, or no more than 6 mites per 300 bees. Over time, you will develop your own thresholds based on the success of your hives, but 2 percent is a good starting point.
After completing an alcohol wash and assessing your results, consider your mite counts while determining your next step. This may mean further pest treatment or continued evaluation. For more information on mite monitoring and pest control, explore our Beekeeping Guide.
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