Alcohol Wash Mite Count Guide: Step-by-Step Protocol for Accurate Varroa Monitoring

The alcohol wash is the most accurate and reliable method for counting Varroa destructor mites in a honey bee colony. Sugar rolls are gentler but less accurate. Sticky boards count mites that have already fallen, not the live mite load. When you need a true count to make a treatment decision, use an alcohol wash.

What You Need

You need a 1/2 cup (approximately 300 bee) measuring device, a mason jar or dedicated mite-washing container with a fine mesh screen lid, 70 percent isopropyl alcohol or rubbing alcohol, a white basin or bowl, and water. Many beekeepers use a commercial counting device like the Varroa Easy Check from Vita Bee Health, which combines the collection container and mesh screen in one unit.

Sample Collection

Collect your sample from the nurse bee area of the brood nest, not from the entrance or honey supers. Nurse bees in the brood area are most likely to be carrying phoretic mites. Hold your collection container directly below a frame of open brood and shake or brush bees into it until you have approximately 300 bees (about 1/2 cup by volume). Do not include the queen in your sample. Cap the container and step away from the hive.

Washing Procedure

Fill the container to cover the bees with 70 percent isopropyl alcohol. Shake vigorously for 30 to 60 seconds. The alcohol kills the bees and detaches mites from the bees' bodies. Pour the alcohol through the mesh screen or lid into your white basin. The mites pass through the screen; the bees remain in the container. Add a second round of alcohol, shake again, and strain again. Count the red-brown oval mites visible in the white basin.

Calculating Your Infestation Rate

Divide the number of mites counted by the number of bees washed, then multiply by 100 to get mites per 100 bees. Example: 9 mites found in 300 bees equals 9 divided by 300 equals 0.03, times 100 equals 3 mites per 100 bees (3 percent infestation rate). The economic threshold for treatment in most published guidelines is 2 to 3 mites per 100 bees from late spring through summer. In late summer and fall, before the winter bee population develops, the threshold drops to 1 to 2 mites per 100 bees because the winter population needs to be as clean as possible.

How Often to Sample

The Honey Bee Health Coalition recommends monitoring every 30 days from early spring through fall, and once before and once after any treatment. In operations with significant robbing risk or neighbors with untreated colonies, monitoring every two weeks in summer gives you better early warning of reinfestation. Log every count with the date, colony ID, and result in VarroaVault so you can track trends rather than reacting to single-point snapshots.