Using a sugar roll to quantify infestation of varroa destructor in honey bee colonies
Updated April 2018, Photos by Andrew Potter (www.andrewpotterphoto.com)
Link to a downloadable pdf with more photos
Plan to monitor for mites at least once each month during the bee season. You may want to check more frequently in late summer, when risk is higher. If you have fewer than 8 hives, or want hive specific data for each hive, test them all. If you want to know the risk for a yard, check at least 8 hives in that yard.
Step 1. Get all your materials ready – make sure they are all clean and dry
Pick a hive, and make sure you have the following equipment, or your mite-check kit (plus water). To purchase a mite check kit, visit www.pollinators.msu.edu/mite-check. Instructions to make your own sugar roll jar can be found at the Bee Informed Partnership Website.
- Powdered sugar
- ½ cup measuring cup
- Container with white bottom (e.g. dishwashing tub)
- Sugar roll jar
- A buddy isn’t necessary, but a second pair of hands often helps.
Step 2. Find a frame with nurse bees.
Take the lid off of your jar, and set it within reach.
Open the hive, without using a lot of smoke - you don't want all the bees running around like crazy. Move down through the hive until you reach the brood nest. Since you want to sample nurse bees, you want to choose a frame that is likely to have them. I usually pick one with a mix of capped and open brood, but any frame that has bee bread on it should be fine. Check both sides to make sure you don't have the queen.
Step 3. Get ½ cup of bees. There are two ways to do this.
Method 1 - In the first method, you can knock the bees off the frame into your tub. Use one quick, hard shake – you want to go hard enough to startle them so they fall. Nurse bees don’t really fly, so they cling to the frames. You may have to shake more than one frame to get ½ cup in the tub.
Don’t worry if bees fly up out of the container – these are older bees, and you are after the nurse bees.
Shake the bees to a corner of the tub. Gently scoop the bees into the cup. Make sure you have as close to ½ of bees as possible.
Method 2 - The second method sampling is useful when the frame has nectar on it – in the shaking method, the nectar can drip on the bees, making them sticky, which will throw off your counts.
Method 2 involves slowly running the edge of the measuring cup along the frame, and letting the bees drop into the cup. You can move the cup either up or down. In the method shown here, you want to be very careful that you are gently tripping the bees into the cup, and not rolling over their bodies.
Once you have ½ cup of bees in the jar, put on the screened lid.
Step 4. Add powdered sugar. Add a few hive tool scoops of sugar.
It isn't important to be precise - you want enough to make sure that the bees are completely coated with dry sugar. I usually err on the side of more sugar, and it is somewhere between 2 tbs and 1/4 cup. If the bees look wet, they may have gotten coated in nectar. Dump them back, and take another scoop.
Step 5. Coat the bees in sugar.
Roll the jar gently, making sure that the bees are sufficiently coated with sugar. Make sure that you don’t tip the jar upside down, and that all the mites stay in the jar until you can count them.
Step 6. Let the bees rest.
Let the bees rest in the shade for at least 2 minutes (can be longer). This is a really important step, that many beekeepers miss. During this time, the bees will heat up and the mites will fall off. If you don't wait, the mites will still be attached to the bees. The powdered sugar doesn't instantly dislodge the mites, but it prevents them from crawling back on once the heat knocks them off. Let them sit in the shade and wait a few minutes. You can put the hive back together at this time, or finish your inspection, or even start on the next hive. Again, if they look wet at this point, the test won't work, so start over - dump out the bees, dry the jar, and collect a new sample.
Step 7. Shake.
After at least 2 minutes are up, it is time to shake the mites into the tub. Shake the jar for 1 minute, shaking hard enough that you dislodge any mites that are stuck to the sides of the jar or in between the bees. A common mistake is to not shake vigorously enough, so make sure you put some effort into it!
Once all the mites are in the tub, you can return the bees from the jar to the hive. They will be a bit worse for wear, but the other workers will quickly clean them up.
Note that these bees still look dry and sugar covered. If your bees look wet, then you may want to repeat the trial.
Step 8. Count mites.
Add some water to the tub, dissolving the sugar so that you can see the mites.
Count and record the number of mites in the tub. A magnifying glass can be useful to see the mites, as they are quite small. Make sure that you are clear on what varroa mites look like. Here, the speck that is pointed out is a varroa mite. The similarly sized speck to the left, however, is not. A varroa mite will be oval shaped, and cinnamon-brown colored.
Step 9. Compare your mite count to your threshold.
As of spring 2018, many experts are using a threshold of 3% infestation (3 mites / 100 bees, or 9 mites in your ½ cup sample). This number may change over time, or by region. Make sure that you check with other beekeepers, extension, and tech transfer teams to learn current thresholds.
Continue to test the rest of the colonies in your yard. If you have only a few colonies, you will want to test all of them. If you have a lot of colonies, test at least 8 in each yard. Make sure that you are prepared with a plan if you find even one colony with high levels of mites. A high mite load in one colony can quickly spread to others.
Congratulations! You have just finished monitoring your honey bee colonies for the varroa mite, the first step in ensuring that your honey bee colonies are kept safe from this terrible pest. If your mite populations are below threshold, take good notes, and enjoy your day. If your mite populations are above threshold, make sure that you take action to protect your bees. For useful documents on what tools to use to manage the varroa mite, visit: https://pollinators.msu.edu/resources/beekeepers/managing-varroa-2017/
Sugar roll step-by-step
1. Gather all your materials
2. Find a frame of brood
3. Collect a ½ cup of worker bees from the brood into your jar
4. Add 2 tbsp powdered sugar to the bees in the jar
5. Roll the jar to coat the bees with sugar
6. Put the jar to rest in the shade for at least 2 minutes
7. Shake the mites out of the jar into a tub
8. Count the number of mites in your sample
9. Divide by 3 to get the number of mites / 100, and compare to your threshold
10. Feel good that you are helping keep your bees healthy!