Varroa Destructor

The Varroa mite, or the Varroa destructor, has become the single greatest threat to the honeybee to date. The Varroa destructor is a parasitic mite  which attacks both the Apis cerana and the Apis melliffera. This mite arrived in the United States in 1987 and has caused enormous problems since. The mite attaches to the body of the bee and feeds off the hemolymph, or the “blood”, of the bee. The process is much like a tick one might find on an outside animal. The Varroa is known as an external parasite which simply means it attaches to its host on the exterior of the body. Varroa are easy to see on a honeybee and look like a red, or brown, dot on the bee. The Varroa will feed on the bee until it eventually dies. No matter what beekeeping philosophy one follows in beekeeping, the Varroa destructor is one pest which must be dealt with. The Varroa destructor can only reproduce inside a beehive and that’s where they are most vulnerable. One point I would like to make is you can guarantee you will have Varroa mites in your hive, it is inevitable, but the key it to keep their numbers to a level which is manageable by the bees themselves. If a person is thinking they are able to maintain a hive with a zero Varroa mite load, I’m afraid they are setting themselves up for disappointment as drone bees transport them to any hive the drone enters. I would also add that having a zero load count may even be harmful to the honeybees, in the long run, as they will not have the opportunity to adapt to this predator.

The greatest damage the Varroa destructor causes is usually economic as it will eventually be the death of any healthy hive if left unchecked. At Ole Bearz Bees, we employ Integrated Pest Management (IPM) techniques to deal with the Varroa destructor. Some of these methods are 1. Using Screened Bottom Boards, also useful with getting Varroa counts using a “sticky board”. 2. We use requeening to break up the brood cycle, thus interrupting the Varroa breeding cycle as well. For much more detail, please refer to the resource page on this website for the book OTS Queen Rearing. I have utilized the principles in this book for the last three years and haven’t lost any hives to Varroa since. Your results may vary, but please give this book some serious consideration in your Varroa fight. There are also commercial queens being bred which have Varroa Sensitive Hygiene (VSH) these queens have proven to pass on genes which allow the bees to clean one another vigorously to remove Varroa. Newer strains are also being developed and some are called “ankle biter” queens. 3. I also use small cell 4.9mm foundation, which can limit the amount of drone brood. Research has been inconclusive at this time regarding the 4.9mm small cell for Varroa control, but I also prefer it as it greatly assists in combating tracheal mites, as the smaller bee produced in the 4.9mm cell has a trachea too small for the mites to enter. 4. Sticky Boards are used to get a count of the amount of Varroa mites dropped over a given  period of time. The mites often fall off the bees and will fall down through the screened bottom board becoming stuck to the sticky board. Sticky boards can be purchased at your local bee supply store, or they can be made using old political yard signs smeared with petroleum jelly. The sticky board is placed below the screened bottom board for a period of 24-72 hours and removed. Once removed, the mites stuck to the board are counted. Once the total number of mites are counted, simply divide by number of 24 hour periods the sticky board was on to get an idea of the 24 hour mite drop count. i.e 150 mites,  divided by 3-24 hour periods, if the board was on for three days, equals 50 mites dropped per 24 hour period.

Two other ways to get Varroa counts are the Powered Sugar Roll and Ether roll. To do a powered sugar roll, simply place about a ½ cup of bees in an empty mason jar which has a mesh screen on the top, ½ cup is about 300-400 bees. The bees should be taken from the brood nest. Add one tablespoon of powered sugar and gently shake/roll the bees and the sugar for about one minute. The powered sugar will make the mites fall off the bees and the sugar is shaken out over a light colored table, dish or sticky board and the mites can be counted. The bees can then be released from the jar, but they may not be very happy! If more than 10 mites are present, then further action is warranted and one would simply follow their management philosophy regarding a course of action. An Ether roll is when about the same number of bees, taken from the brood chamber, are put into a mason jar and automotive starting fluid is sprayed into the jar for about two seconds. The bees, and mites will die, the bees will also regurgitate any consumed nectar and that will make the walls of the jar sticky. Shake, and roll, the jar for one minute to knock the mites loose and then lay the jar on its side. Once the jar is on its side, roll the jar 3-4 complete turns to get all the mites stuck to the side of the jar. Once this is complete, count the number of mites stuck to the side of the jar, then count the number of bees in the sample. One then divides the number of mites by the number of bees to get the percentage of infestation and take action accordingly. For the Ether roll in one mite is present per every 100 bees, take action.

When to test is also important. I will give recommend thresholds for using both the Sticky board and the Ether roll method. For winter survivor hives testing can take place up to mid March, if more than two mites are present, using an ether roll take action or if more than 9 mites are found using the 24 hour drop and a sticky board. Spring testing can take place from late March through Mid June and action should be taken of more than 10 mites are found using 24 hour drop on sticky board, or if more than 2 mites are found per 100 bees using an ether roll. Fall testing can be done from Mid June through late August and action should be taken if more than two mites are present per 100 bees are found using an Ether roll or if 12 mites are found using the 24 hour drop using a sticky board.

There are other ways to address the Varroa destructor which are considered more natural than chemicals and they are essential oils, organic acids like oxalic acid and mineral oil. The last step of treatment is chemical treatments and Apistan, Checkmite+ and Apilife var are all options, however one must take great care to follow the application label as it is easy to make a mistake when dealing with chemicals.

0 replies

Leave a Reply

Want to join the discussion?
Feel free to contribute!

Leave a Reply

Your email address will not be published. Required fields are marked *