The Powdered Sugar Method (Sugar rolling) provides a good estimate of the number of Varroa mites on the adult bees. It is not as accurate as the alcohol method, but it does give you a good gauge or still the opportunity to do it more often without diminishing the numbers.
This method has the advantage of not killing the bees.
1. The first step is to make a shaker container with a cover. An easy method is to use a wide-mouth canning jar. Use a ring type cover. Cut a circle of mesh of a size that won’t let the bees through. I had extra screening from my nucs, but some use hardware cloth the size of the cover that fits in the ring and use it instead of the cover.
2. You will also need something white to shake the mites and powdered sugar into/onto. I use cheap white disposable paper plates set in a frisbee. You can just shake them onto a paper plate if it is not windy. Any white container works.
3. Shake about 300 bees into the quart container. You can shake the bees from a deep frame into a piece of large tupperware/plasticware to help scoop them later out of the container. Use a standard 1/2 Cup measure and get yourself some bees from the Tupperware before they all fly off. This step always amuses me. Half cup of bees please.
4. Approximately 300 bees. 1/2 cup = approximately 300 bees. You will have to shake the bees in, then tap the bottom of the container to get all the bees on the bottom of the container to measure them.
5. With the bees in the container place the screened lid on top of quart jar and secure.
6. Put about 2 Tablespoons of powdered sugar into container. Shake the bees with the powdered sugar until they are well coated. Let the container sit for about 1-2 minutes. *Honestly, I do this step as I prep the jar usually in the beginning. Sometimes working alone and with a bunch of annoyed bees it’s just more efficient to load the jar before suiting up…and before scooping said annoyed bees.
**Either way, the bees need time to warm up the sugar and should be left shaken up at least 1-2 minutes before shaking the sugar and mites out.
7. Tip the container upside down over the white container and shake the powdered
sugar and mites firmly out through the screen.
8. Continue to shake for at least one minute to be sure you have all of the mites. Go until most of the powdered sugar looks in container.
9. Get out your spray bottle of water and spray the powdered sugar with mites until the mites clearly appear. I usually spray all dried sugar to wet. Count the number of mites in the powdered sugar. Really, if you have trouble seeing them you can add a small amount of water to dissolve the sugar, making the mites much easier to see.
11. Return the bees to their colony. I usually empty them out directly onto the top of the frames. I might hit them with a puff of smoke then close them back up in the hive. Their sisters will help clean them off again soon enough.
12. The bees will survive. Once they are cleaned up they can go back to work
If you know how many bees were in your sample, you can estimate the number of mites per 100 bees. If there is brood in the colony when you sample, you should double this number to factor in the amount of mites in worker brood. For example, if there are 5 mites / 100 bees, the total infestation is probably 15 mites/300 bees. If your colony has over 10-12 mites/300 bees, you should consider treatment
Calculation: # of mites counted/300 x 100 = (%) Percent of infestation