Varroa mites have been in the United States since the late 1980s and are considered a universal problem. If you are bee farming you most likely have varroa mites in your beehives. Like ants, healthy bee colonies can take care of a few mites. The problem comes when the hive is weak and the mites are allowed to multiply and eventually take over. Fortunately, varroa mite treatment isn’t hard, you just have to be diligent.
Varroa mites are about the size of a pinhead and are visible to the naked eye. They attach themselves to a foraging bee, and like a tick will feed on the bees “blood” (hemolymph fluid). When the foraging bee returns the hive, if the mite gets past the guards, she will hop off the bee and start looking for the drone brood. This is where she does her damage.
The varroa mite will enter an uncapped brood cell, drone cells are her preference, and hide until the cell is capped. Then she will begin feeding on the fluid in the larva and lay eggs. The first to hatch is a male who then mates with his sisters that hatch later. When the bee emerges from its cell, the varroa mites also emerge and go on the hunt for a new uncapped cell to repeat the reproductive process. Varroa mites reproduce at an alarmingly fast rate. They can quickly weaken the hive enough that the hive becomes susceptible to other pests and viruses.
Russian bees are considered to be resistant to varroa mites. This doesn’t mean that varroa mites won’t come into a Russian bee colony; it just means that Russian bees have certain characteristics that help them better manage varroa mites than other bees. The same is true of “survivor bees” or resistant bees, which are bees that have been living without chemical assistance for years. These bees are fighters and will aggressively defend their hive against any invader; even if it means seeking out mites already in capped brood, uncapping and removing the pupa and destroying the mites.
Screened Bottom Boards to Reduce Bee Mites
Using screened bottom boards is another way to help monitor and control mites. Some mites will naturally fall off the bees and to the bottom of the hive. When you use a screened bottom board, you can put a sticky trap on it to keep all the fallen mites from re-entering the hive. This also allows you to count the mites and make sure the bees are able to keep the mite population under control. You should have no more than 50 mites on the sticky board over a one or two day period of time. If you have more, you will need to help the bees get rid of them.
Using a screened bottom board will also help with ventilation which means not as many bees need to be fanning during the hot summer. This allows them to do something else, like defend the hive. The screened board will need to be replaced with a solid bottom board during the winter.
Dust Bathing to Reduce Bee Mites
Dusting the hive with powdered sugar is a common varroa mite treatment. Just like dogs and chickens dust in the dirt to help with pests, bees can dust in powdered sugar. Most commercial powdered sugar has cornstarch added as an anti-caking agent. Bees should not consume cornstarch and you should not feed commercial powdered sugar to bees. However, because the bees don’t consume much of the powdered sugar while dusting many beekeepers use commercial powdered sugar with cornstarch. Some beekeepers only use commercial powdered sugar without cornstarch. And some beekeepers make their own powdered sugar. To make your own powdered sugar, put half a cup granulated sugar into a blender or coffee mill and give it a whirl until it’s a powder.
When starting beekeeping you’ll often find opposing views or even opposing research studies. The best thing to do is to read in depth about each viewpoint and then decide what is right for your beehives.
Drone Trapping to Remove Bee Mites
Drone trapping is another non-chemical varroa mite treatment. The queen needs about 10-15% of the brood cells for drones, usually around the perimeter of the frame. However, you can coax her into making full frames of drone brood cells. You need to remove two full frames of worker brood and replace them with empty frames. This will signal the hive to get into drone production and they will (usually) cover both sides of each frame with drone cells. After the cells are full and capped, you can remove the frames from the hive and destroy the brood which has the varroa mites in them.
The downside of this is that drones are a sign of a healthy hive, so you certainly don’t want a hive without drones. The upside is that you can destroy a lot of varroa mites at one time which will get their population to an amount that the bees can naturally handle. This should only be done once the above measures have been taken.
Enlisting Herbal Help to Repel Bee Mites
Thyme is reported to be a varroa mite deterrent, so consider planting thyme around your apiary. Thymol which is derived from thyme is an ingredient in both Apilife Var and ApiGuard, two commercial products that are safe for use inside the hive as a varroa mite treatment. If you need to use a pesticide, these are ones you want to start with because they don’t cause any harm to the bees and only small amounts are absorbed by the wax.
Another pesticide, formic acid, is used when there is a huge sudden influx of varroa mites into the hive. The commercial name is Mite-Away II. This is effective, doesn’t harm the bees and isn’t absorbed by the wax. However, it is irritating to the bees so it should only be used when you are sure there is a need for it.
Plastic Strips Have Downsides
There are also plastic strips that contain chemicals that do a great job of killing the varroa mite. However, the mites that survive become resistant to it. It’s absorbed into the beeswax. The queen will begin to lay fewer eggs and will die young, and the drones reproductive organs become damaged by using these chemicals. So, while it is an inexpensive quick fix, it becomes a long-term disaster for the hive. Just like using moth balls for wax moth treatment, you kill the pest but you also kill the hive.
I recommend never using these plastic strips for varroa mite treatment. If the hive cannot combat the varroa mites with the help of screened bottom boards, powdered sugar dusting, drone trapping and using botanicals, then the hive will not survive long-term even with using chemicals.
Managing beehives pests is a tricky balance. You want to give the bees enough help through integrative pest management that they stay strong and healthy. But you don’t want to give them so much help that they become a weaker hive. Healthy hives can manage pests on their own. The beekeeper’s job is to make sure that the pest population does not overrun the hive.