Using a sticky board
In order to monitor the mite levels in a hive, you'll need to use a sticky board. A sticky board is nothing more than a piece of 1/8 inch thick, white corrugated plastic. Most have a graph printed on them so that counting the mites is easier and more accurate. The boards work in conjunction with screened floors to measure what is called "24-hour natural mite drop" from the colony. You cannot use a sticky board with a solid floor, which is another good reason not to use solid floors.
The first step in using a sticky board is to make it sticky. This is done by using a paper towel to coat the graphed part of the board with a very thin film of Vaseline. Next, you simply slide the board sticky side up, under the hive, using the space provided at the rear of the floor assembly. Push the board under the hive until it stops.
Now, you simply walk away and wait for 24 hours, before returning to remove the sticky board from under the hive and examine it for mites. When you remove the sticky board, use care not to allow the top of the board to scrape against the bottom of the hive, so as not to remove any mites from it. Mites that have naturally died, or have otherwise lost their grip on their host bee and fallen to the bottom of the hive, will now be stuck in the thin film of Vaseline on the board. Many will be dead, but some will be alive and it is common to see their tiny legs kicking as they struggle to free themselves. We did a 24-hour mite drop on one of our Warre hives for the purpose of getting the photo below. Our hive's mite drop was one. Can you spot it? Hint: The yellowish particles are just hive trash (bits of comb, mostly).
Before we talk about the results and what they mean, we want to emphasize that you should do at least one fall treatment no matter what the results of the 24-hour natural mite drop test are. Here are some guidelines that are intended to help you put the test results into perspective:
0-3 Mites counted - Your hive is probably very healthy and cause for concern for varroa mites is low. Perform one varroa treatment and check the hive again in the spring, at least six weeks before the first honey flow.
3-15 Mites counted - This would be a typical result, and most likely indicates a healthy hive with a minor varroa infestation. Nip the problem in the bud now, and it will be unlikely that the hive will have any issues the following spring. Perform a varroa treatment and then do another 24-hour natural mite drop test in 7 days. Repeat until the mite drop is 3 or fewer in 24 hours. Two or more treatments may be needed. Check the hive again in the spring, at least six weeks before the first honey flow.
15-40 Mites counted - A mite count this high indicates that the colony is struggling with a significant infestation of varroa. The colony is at risk of collapse if the numbers are not brought down. Proceed as directed in the paragraph directly above, except wait until 7 days after a second treatment is done before you do the second mite drop test. Treatments should be performed every 7-10 days, and it is likely that at least three treatments will be needed. Check the hive again in the spring, at least six weeks before the first honey flow.
More than 40 Mites counted - A colony that drops this many mites in 24 hours is severely infested with varroa. There is little chance that the colony will survive a winter with numbers like these. If you are not too strongly opposed to using one of the milder chemical treatments (such as Apistan), you may want to consider that in order to save the colony. We do not use chemicals in our hives, but they are an option. The choice of whether or not to use one is for you to make. Otherwise, perform 4 varroa treatments, 7 days apart, and then do another 24-hour mite drop test. Continue to treat organically, if necessary, until the numbers come down or until the weather is such that you can't treat any longer, and then just hope for the best. Check the hive again in the spring, at least six weeks before the first honey flow.