Mite monitoring boards don’t control mites at all. They are a method of assessing the mite levels so you can decide what, and when, to do something about the mites before they can harm your colony. Years ago, screened bottom boards were promoted as a way to reduce the mite numbers by allowing them to fall out of the hive. Sticky surfaces were used underneath the screen to make sure the mites couldn’t crawl back in. Unfortunately, too few mites fall out to make a significant decrease in the total mite population. However, that doesn’t mean that mite monitoring boards aren’t a valid mite population assessment technique. If you run a 3-day count every week, you’ll get actionable information about when you need to treat. There are other good methods to measure mites, but none as easy or non-intrusive as sticky boards. And in cold climates, only sticky boards can be used during the winter.
You could do that, and many beekeepers do. But you risk both over-treating and under-treating. Over-treating happens when you do a pre-scheduled treatment that wasn’t actually needed and under-treating is when you have an unexpected spike in your mite numbers. This is especially true in the fall when previously treated bees can sometimes experience a late-season mite increase. If you only treat by the calendar, you’d never see the danger until it was too late. Constant weekly monitoring confirms that you are still on track, or warns you that you need to add an extra treatment to keep your bees healthy and free of diseases as they head into winter.
The reason to do a longer count and then average the number is because mite drop rates can vary somewhat from day to day. Many environmental factors, hive conditions, and even whether a beekeeper has recently worked a hive will affect the drop rate. To reduce variation from extraneous factors, an average over the longer period is used. If you have difficulty identifying mites on a board, start out with a single 24-hour count to reduce the amount of debris on the board and make the mites easier to spot. But work towards doing 3-day counting periods as soon as you can to improve the quality of the information you are gathering.
Actually, the best time to start is three days before you plan to open the hive again because this permits the longest disturbance-free period before the count begins. If you usually work your bees on the weekend, start the count in mid-week. Pull the board and count the mites before you begin the inspection. One of the advantages of sticky boarding is that you can insert the boards in the evening, or even after dark, because you are working behind the hive.
If you have been sticky boarding weekly and one week you see a number that’s double or triple, you should immediately start another three-day test. But don’t panic! Most often this is a one-time spike, and the mite numbers will quickly return to the baseline trend. However, if the second test’s results are still high, you should act immediately as you may have had a large influx of mites due to drifting or robbing. And without that weekly test, you would never have suspected a problem was brewing. This is why a single test, or even a now-and-then monitoring program is usually not successful. You need to do it every week in order to see the big picture clearly enough to make good treatment decisions.
Counting mites is a separate thing from using chemicals to treat for them. Even treatment-free beekeepers need to know about the health of their hives, and mite counts are an important part of that assessment. Counting mites also allows you to judge whether your non-chemical mite management tactics (re-queening, brood breaks, drone comb removal, powdered sugar dusting, etc.,) are doing the job.
Close up of Varroa mites on a sticky board.
Perhaps, but because mites have spread around so thoroughly, it would be a rare colony that doesn’t have any. Keep on using the sticky board. If after a few weeks you still aren’t seeing any, then it may be because you aren’t recognizing the ones that are there. They will be small, reddish-brown ovals, and with a magnifying lens you can often see a little fringe of mouth parts and legs along one of the long sides of the oval. They are a bit smaller than sesame seeds on a hamburger bun. You can also take the board to an experienced beekeeper and ask them to point out any mites. But even if you have no mites now, that will certainly change over time. So keep on checking every week.
Solid board goes underneath the screened board, facing towards the back of the hive. Open slot in the back is where the tray or sticky board are inserted.
This can be perplexing at first! The trick is to place the solid bottom board (the lower one of the pair) so it faces the back of the hive and put the screened bottom board on top of it, facing the front of the hive where the bees will use it as the entrance. This puts the opening slot where the plastic board or tray slides in at the rear of the hive. Having it behind the hive means you can tend the boards without disturbing the bees at all. Close up the back opening with tape to keep bees, ants and other critters away from the sticky surface. You can also make a wood or foam insert to close up the opening in the back. If you normally have your hives tilted slightly forward to allow any rainwater to drain out, it should be reversed if you have the two boards stacked up. Tilt the stack slightly backward so any moisture can run out the back.