Varroa IPM - Intergated Pest Management

The IPM approach is simply this—utilizing a series of methods for the long-term control and prevention of Varroa mites. The combination of these different methods gives the beekeeper and the bees a much broader chance of winning the battle with Varroa mites. 

Cultural

Resistant stock

The name describes the method. Keeping mite-resistant stock helps to ensure your bees’ ability to manage mites before you as a beekeeper even step in. You notice I used the word “keeping.” One of the key aspects of successful beekeeping is maintaining mite-resistant queens in order to stay on top of the genetic attribute these bees carry. They are keen at sensing the growing mite under a capped brood cell—they then uncap the cell and remove the larvae (mite and all), discarding it from the hive or consuming it. The mites in turn die, and that’s the end of that! Where we as beekeepers go wrong is when we purchase a great Varroa-sensitive hygienic (VSH) queen or hive and leave it at that. Even with mite-resistant stock, testing and other control methods should be used when necessary. Requeening yearly to maintain the VSH genetics should be your priority and will definitely result in healthier bees and lower mite loads.

Small-Cell Comb

Although on the graph, small-cell comb hasn’t been able to prove itself a contender in the Varroa mite war. It was thought (and is still thought by some) that a reduced cell size encourages better hygienics and that smaller cells would mean reduced mite production. This hypothesis has fallen short and has even been challenged, with some findings suggesting that small-cell comb may generate greater mite loads in certain cases.

Brood break 

Brood break is a commonly known method for controlling the reproduction of Varroa mites. A brood break simply means stopping the brood cycle for a time in order for the capped brood to emerge (mites included) and stop providing a place for the mites to grow (under a capped cell). An example of a brood break is making splits. The process of splitting involves dividing the brood nest and introducing a new queen (in a cage or cell), which causes a break in the brood cycle. Caging a queen (seen below) is also a well-known method for creating a brood break. You can simply make a “push-in” queen cage out of screen wire (see picture below) and place it over the queen and several attendants. Some suggest doing this for three weeks to get through a full brood cycle. Brood break is arguably one of the best methods to stay ahead of Varroa mites. Even making a brood break for just a few days can make an impact on Varroa reproduction.

Mechanical - Killing by physical means

Anytime we can simply trap a mite while it’s not in a cell, we have a much better chance of slowing the propagation.

Mite trapping

Mite trapping is simply what the name implies. This makes sense when you factor in the length of time the drone is capped (24 days) compared to worker brood (21 days). That additional 3 days allows for a significant increase in productivity in mite production. Therefore, it stands to reason that trapping mites would involve utilizing drone brood.

A drone frame is a tool designed specifically for this purpose. Drone frames are made of plastic and formed with a larger cell structure than standard foundation frames. This larger cell invites the queen to lay an unfertilized egg (drone). The Varroa mites will then favor this frame over worker brood, giving you a full frame to be removed once it is fully capped—taking with it the Varroa mites growing inside. It is very important to remove this drone frame prior to the drones emerging. If you leave it in the hive, you run the risk of having a Varroa mite bomb in the colony. Once capped, simply remove it, freeze it, then decap the frame and feed it back to the bees for cleaning and reuse. Or, if you have chickens, they love to clean it up as well.

Screen bottom boards 

Utilizing screen bottom boards is another mechanical method. Commonly used for ventilation, it can also be used to help control Varroa mites. Phoretic mites naturally drop off as the bees work and move around in the colony. Using a screen bottom board as opposed to a solid bottom board can prevent them from crawling back up into the colony, therefore reducing the active mite population. Not only that, some screen bottom boards double as Varroa traps. The drawer style (opens in back) easily slides in and out for installing and checking a sticky board while doing mite-drop testing. For added ventilation in summers, simply remove and store the drawer slide until needed for overwintering.

Sugar Dusting With Powdered Sugar

This method has been around for a long time, but to borrow a phrase from a popular show, “This myth is busted!” There is simply no evidence that powdered sugar dusting reduces your mite load.

Theory: Sprinkle powdered sugar over the top bars, and because the bees naturally want to groom it off each other, this hygienic behavior in turn causes the mites to drop off through the screened bottom board, therefore reducing your mite population. Unfortunately, most of the mites don’t actually fall out of the hive in numbers that make a difference. Therefore, it is not a viable method.

Chemical

This category includes both synthetic and natural organic compounds, such as thymol-based products. Beekeepers can reasonably maintain an organic status by using these natural compounds. It’s important to note that most of these “soft” chemicals aren’t suitable for “knockdown” use when needed. In other words, if you have a very high mite load, using synthetic miticides will provide the quick kill needed to save a colony—anything less may not. For more information on available treatment options and when they are most effective, read Varroa Destructor: Treatment Options Made Easy

Take Away

Decide who you are as a beekeeper. Are you an all-in, do-anything-you-can type to control Varroa mites? Or are you a passive, less aggressive, start-at-the-bottom-and-work-my-way-up type? Either way, committing to stay on top of Varroa mites in your colonies is the only choice we have to be successful beekeepers. As I said at the beginning of this article, utilizing IPM (multiple methods to control Varroa mites) will ensure you are doing all you can to keep your mite loads down—giving your bees the very best chance they can to stay healthy and thriving!

By: Chari Elam