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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. 

Mechanical– Killing by physical means Anytime we can simply trap a mite while it’s not in a cell gives us a much better chance of slowing the propagation. Mite trapping is simply what the name implies. As you can see by the diagram below – mites much prefer laying eggs in drone brood.

Graphic by: Penn St. Extension

This makes sense when you factor in the length of time the drone is capped compared to worker brood. That additional 3 days allows for a significant increase in productivity in mite production. Therefore, it stands to reason “trapping mites” would involve utilizing drone brood.

Image by Robyn Underwood. 

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 to worker brood, giving you a full frame to be removed once 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 left in the hive to emerge, you run the risk of having a Varroa mite explosion 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.

Powdered sugar dusting Directions for this method – Sprinkle a liberal amount of powdered sugar across the top bars inside the hive and use a bee brush to gently spread it around, allowing it to fall down between the bars on to the bees. The bees then begin to groom themselves, causing the mites to dislodge and fall off through the screen bottom board. I can tell you first hand this isn’t my favorite method, and it’s results just aren’t that good and research backs that it up. At first glance you would think it’s a great idea but…not so much. The bees don’t like it – and studies have shown you would have to repeat this process multiple times to make any difference and even then, it’s not significant. Cultural control refers to controlling Varroa mites by reducing reproduction. Anytime we can slow the reproduction of the Varroa mite (or any pest for that matter), our job as beekeepers gets easier.

Resistant stock The name again describes the method. KEEPING mite resistant stock helps to ensure your bees’ ability to manage mites before we as beekeepers 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 decap the cell and remove the larvae (mite and all), discarding it out of the hive or consuming it. The mites in turn die and that’s the end of that! Where we as beekeepers go wrong – we purchase a great VSH (Varroa Sensitive Hygienic) queen/hive and leave it at that. Even with mite resistant stock, testing and other control methods should be used when necessary. Re-queening yearly to continue the VSH genetics should be your priority and will definitely result in healthier bees and lower mite loads.

Small Cell comb In the 1950’s as honey and bee production started increasing, the cell imprint on foundation was enlarged ever so slightly (from 4.9 mm to 5.4 mm) to increase the honey yield as well as the size of the bees (bigger bees, more honey). The scientific community has long debated that this larger cell has led to the increase “space” for the Varroa mite to reproduce, therefore, reducing the cell size back to its original size will reduce the reproduction of the mite. The argument being, in nature – bees build smaller comb than that imprinted on our purchased foundation. I haven’t found this to be true. When our bees are left to draw their own foundation, almost always it’s larger than the imprint not smaller. This is my experience and may not be yours. Concluding, the use of small cell foundation is thought by some to be a reproductive control method.

Brood break A commonly known or unknown 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, 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 3 weeks to get through a full brood cycle. Brood break is arguably one of the best methods to stay ahead of Varroa mites. Even just a brood break for a few days can make an impact on Varroa reproduction.

Image by Robyn Underwood. 

Decide who you are as a beekeeper. Are you an “all in” – “do anything you can” 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

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