How Varroa Mites Build Up Immunity to Commercial Miticides.

Why would I, as an Alternative beekeeping advocate, write about the use of commercial miticides? First and foremost for me personally, the most important thing is keeping bees alive.
Everyone’s bees. Also, I consider myself an intellectual Alternative keeper, in that, I wouldn’t “take anything off the table” in my pursuit to keep bees alive. Though I don’t use miticides- I will do everything I can to help keepers who do. Varroa mites have the ability to continuously built up resistance to commercial treatment products. Each new mite control product that comes on the market has a useful life of less then 10 years. It is not defects in the products. The products are effective when first introduced. The Varroa mite has developed a method of quickly building up an immunity to each new product. What exactly is happening that makes it possible for the mite to build up resistance so quickly with every new product? It’s predictable, it’s coming, it is going happening. Producing another form of miticide produces another population of immune mites. Developing new miticides doesn’t solve the resistance problem. What is the process that breeds populations of super mites that build up an immunity to each new product introduced by the beekeeper? Once we find the mechanics of the immunity build up process, we can develop methods of management that prevent that process. If we as beekeepers can “short circuit” the mechanics of the immunity process it would enhance the effect and efficiency of any treatment to control Varroa mites.
In treated hives, over 40% of the mites that fall to the bottom board are still alive. 1. They received what is referred to as a sub-lethal dose of miticide. The mites got enough of a dose to temporarily incapacitate them but not kill them. This segment of the mite population recover on the floor of a solid bottom board hive, reattach to bees approaching near them, and return back up into the colony. Mites receiving and surviving sub-lethal doses of a miticide, returning back into the hive and breeding generation after generation build up an immunity to that miticide.
One way of “short circuiting” the immunity process is using screen bottom boards. SBB’s are literally and figuratively the foundation of a hive as part of a Integrated Pest Management program. Screen bottom boards must be constructed correctly and used correctly to provide the most benefit as an enhancement to treatments and the prevention of mite immunity buildup. Most treatments work best in an enclosed hive so a SBB with a sliding board under the screen is more desired then an open screen floor. The 40% of mites still alive after receiving a sub-lethal doses of miticide fall through the screen, are unable to reattach to a bee, and die on the sliding board under the screen. Mites looking to reattach to a bee can sense bees within 1 inch away. It is important to construct SBB’s with the sliding board an inch and a half or more below the screen. Live mites that fall to the sliding board beyond “sensing” distance will wander aimlessly on the board for a short time looking for a bee, then sit and die waiting for a bee. Sticky boards can be used on SBB’s with sliding boards closer then one and a half inch to the screen during treatments. The sliding board SSB is also a valuable tool to the beekeeper for easily monitoring mite populations and observing the need for and efficiency of treatments.

1. Chapleau, J.P. Experimentation of an Anti-Varroa Screened Bottom Board in Context of Developing an Integrated Pest Management Strategy for Varroa Infested Honeybees in the Province of Quebec (2002)

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Ernie Schmidt

Together we are about to start down the path of Alternative Beekeeping. Each month I will discuss and share the joys, methods, philosophies, and realities of keeping bees in Top Bars and Warres, along with other different and unique hive styles and methods. There will be times I get straight to the point and other times I will meander about, but always remember - "It’s all about the bees"

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