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.
What is an alcohol wash?
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.
How often should you check for varroa 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.
Selecting bees for an alcohol wash
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.
Does an alcohol wash kill the bees?
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.
Varroa EasyCheck or Varroa Mite Sample Bottle sampling device
Half-cup measuring scoop
Isopropyl alcohol and water mixture (1:4 ratio) or non-foaming, winter windshield washer fluid
Large plastic tub; a big cat litter box is a good choice
Timer
Fine mesh strainer
Quart-sized plastic container to use during straining
Larger, lidded container to collect used sampling fluid if you are doing multiple tests
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.
Preparing to test
Fill the alcohol wash device of choice. Pour in an isopropyl alcohol mixture or a non-foaming windshield washing fluid until the fluid covers the bottom of the inner perforated cylinder.
Find and, if possible, isolate the queen. You can temporarily place the queen and her frame in a nuc box.
Select your bees. The bees with the most mites on their bodies are likely to be the nurse bees caring for the open brood. Those are the bees you want to test. Select a frame that is at the outer edge of, or just outside, the brood area and look the frame over carefully to make sure the queen is not on it. Then, collect a sample of 200 to 300 bees. As soon as your sample bees are off the frame, put the frame back into the hive to keep the brood warm and safe.
How to collect bees for sampling
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.
Instructions for an alcohol wash test
Shake the test container once to wet the bees, then open and add fluid to the upper line of the outer container.
Shake the container gently for 60 seconds. You can shake vertically, horizontally, and in a circular motion, which helps separate the bees and mites.
Hold the container up to the light and count the mites that rest at the bottom.
Divide the mite count by 3 to get a percentage (e.g. 15 mites per 300 bees equals 5 per 100, or 5 percent).
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.
Evaluating alcohol wash results
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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