The #1 killer of beehives (at least here in Utah) is the Varroa Mite. To be a successful beekeeper requires knowing your mite numbers. Testing and treating for mites is a very important part to beekeeping. If you haven't treated for mites during the year then you most likely know the outcome by the following spring. That usually ends up being a struggling or dead hive.
Testing for mites can be challenging for beekeepers because to get an accurate count, requires doing the test properly. Here are some common mistakes often made when testing.
Sample nurse bees not foragers - For best results. Making sure to shake bees off of frames where open brood is present to get the most nurse bees during testing. Don't just shake off any frame of bees.
Powder sugar shake vs. Alcohol/Dawn soap solution wash test - The Alcohol/Dawn soap solution wash method does kill the 300 bee sample, the Sugar Shake doesn't. But the test results will be more consistently more accurate in the Alcohol/Dawn soap wash method. We recommend using the Alcohol/dawn soap solution wash
Improper execution of test gives improper results - Making sure shaking the bee sample with the powdered sugar method hard and long enough (So hard you'll feel like you may be hurting them) to dislodge the mites to get an accurate count. Not wanting to harm or kill your bee sample whether the powder sugar shake method, or the alcohol wash method is totally understandable.. I felt the same way myself when I first started testing. But which is worse.. losing a few hundred bees out of the 60-80,000 in your hive or possibly killing off the whole winter colony due to improper testing and treating. I liked listening to one of our State Inspectors Joey Caputo a couple years back during a varroa test that he did. He tried to help the new beekeepers there understand that the honeybee will sacrifice its life and will die to sting an intruder to help save the hive. We are doing a similar sacrifice of 300 bees which is less than 1% of the population to potentially save the hive from a large infestation of the varroa mite which could ultimately be the death of your hive. This will help you determine the lifespan of your hive heading into fall/winter. So not having skewed results from improper testing because we feel sad for those bees that were shaken or sacrificed can ultimately determine the fate of your hive and the neighboring hives in your as well. In addition, you could also be saving $160-$200 in bees the next year.
How to determine the percentage of mites in your hive.
When you count the mites in your test then you are figuring out how many mites per 100 bees. Since 1/2 cup =300 bees approx. then you will divide the number of mites in the test by 3 and that will give you your percentage. (i.e. 7 mites in test, 7 divided by 3 = 2.33%)
When should I treat?
We want to stay 1% or below infestation. When you have results over 1% on your mite count, then you should start thinking about treating soon. If your mite count is really high then you may need to use something a little stronger and it may require multiple treatments that will bring down the mite count to manageable numbers. It is much better to keep the mite count in the hive at a lower level through out the year than to try and correct an out of control mite population when your hive is on the verge of entering winter with very little time to correct the problem.