Folks have been asking about my mite-wash cups and how to make them. I’m glad of this because this is key to breeding queens, preparing for winter, pinpointing reasons for losses and a lot more. All this and a ton more is in the Basic Course (click here to find out more).
Know what is going on
Better than being blind to what is happening in your colonies is being able to see when a serious situation is developing. This gives you valuable information beyond just being able to take action when needed. It can help you see patterns of cause and effect and what factors lead up to high or low mite levels in a colony. You will not be wondering what happened and repeating the same mistakes.
Because it is possible for a newly purchased colony to already be badly infested with mites, every new beekeeper should know how to assess the mite levels in their colonies.
What we are after is an “infestation rate”, that is, how many mites are in every 100 bees. To get this we need to gather some bees and separate the mites from them. A video on the Honey Bee Health Coalition web site (click here) titled “Sampling Methods” covers two ways to do this, the sugar shake and the alcohol wash. In my opinion the sugar shake has too many drawbacks. Inspired by ideas from Randy Oliver, I have slightly modified the alcohol wash method, which I explain below, to take far less time and less expense, yield more accurate results, and is quite efficient even with a large number of colonies. You just have to take the time to set up your system.
Making your Mite Wash Cups
First you will need to make yourself a mite wash cup, or set of cups. I use two 20-oz clear plastic restaurant cups with lids (very cheap) and a piece of mesh screen from an onion bag for each mite wash cup. The screen must be small enough to not allow bees through.
Take one of the cups and cut 3/4 inch off both the top and bottom of the cup. I used a razor blade. Cut the mesh bag so that it will cover the bottom of the cup, wrap up the sides, and out the top. Nest this inside the cup that was not cut. This forms 2 chambers separated by a mesh screen. You should be able to get the lid on over the screen. You could use a much smaller piece of screen if you super-glue the screen to the sides of the cup instead of bringing it all the way up and out the top. The glue will need to hold reliably to the smooth plastic and be unaffected by alcohol.
I made a box that would hold enough cups to do a yard of 20 hives (see image below). You will need 1.5 cups of 50% alcohol in each cup. You can purchase 99.9% pure isopropyl (rubbing) alcohol by the gallon for a very reasonable price and dilute it 50% with water. Put 1.5 cups of diluted alcohol in each of your mite wash cups. The lids do not prevent leaking so when you go to your hives, transport your cups in such a way that they do not spill (as in the box shown below). Always take along extra alcohol just in case. Lastly, put a piece of masking tape on the lid to mark the hive number on.
Taking your samples
To take your samples in the field, bring your cups with alcohol, a tub or bucket to shake bees into, and a 1/2 cup measuring scoop, and a sharpie marker or paint stick. Bring along extra masking tape and alcohol. The video below shows how I gather the bee samples. WARNING: I did my best to prevent related videos from showing up at the conclusion of the video. However to be sure to prevent offensive images from showing up at the conclusion, you may want to pause the video just before it finishes and move the red dot back to the beginning.
Collecting the bees is all you need to do in the bee yard. Reducing the time in the bee yard is always a good thing, especially if the weather is unpredictable. You don’t have to shake the alcohol sample to dislodge the mites at all, which keeps your alcohol clear for many re-uses. Return home with your samples and give each one a quick stir as shown in the video below. WARNING: I did my best to prevent related videos from showing up at the conclusion of the video. However to be sure to prevent offensive images from showing up at the conclusion, you may want to pause the video just before it finishes and move the red dot back to the beginning.
After stirring each sample, let them set for a standard amount of time, at least 4 hours. I let them set overnight and find 95% to 100% of the mites in the bottom chamber below the bees. Re-washing the sample with all the shaking that is normally recommended does not recover any additional mites in lightly infested samples, and only 5% at most in very heavily infested samples. The video below shows removing the bees and counting the mites. WARNING: I did my best to prevent related videos from showing up at the conclusion of the video. However to be sure to prevent offensive images from showing up at the conclusion, you may want to pause the video just before it finishes and move the red dot back to the beginning.
The Varroa Easy Check is a commercially available tool that utilizes the same double-chamber concept described above, but is much more expensive and uses a lot more alcohol. The perforations in the basket also cover such a small percentage of its surface that I would worry about mites not coming through. This would be a worthwhile investment if you only have a few hives.
You may want to count the bees from some of your samples to make sure you are getting the correct amount in each scoop. 1/2 cup should be close, on average, to 300 bees, while 1/3 cup should be close to 200 bees. The accuracy of our methods determines the accuracy of your results.
What your numbers mean:
If a colony is raising brood, you will want to see less than 2 mites per 100 bees (total of less than 6 mites in a 1/2-cup sample of bees). If you see more than that, something should be done to reduce the mite loads. If you have a winter season in your climate, mite loads should be reduced to below 2% at least 6 weeks before the end of plant bloom. If you ever find more than 7 mites per 100 bees (total of more than 20 mites in a 1/2-cup sample of bees) it might be impossible to save the colony even if you deal with the mites because the colony is most likely already heavily infected with viruses. The most important seasons for monitoring your mite loads are June through September. Mite loads in September will give you a good indication of which colonies will die in the winter due to mites.