Varroa mites first became a threat in Australia. Recently, an Australian ABC news station reported, “Varroa mites discovered on ship in Australian waters… Thousands of Asian honey bees carrying devastating varroa mites have been discovered on a foreign ship berthed in Sydney…”
The varroa mite is a tiny parasite which attacks bees and eventually destroys their hives.
While Australia is now considered free of varroa mites, fears still exist. A breakdown in quarantine procedures could spell disaster for Australian beekeepers. However, Australia’s worry is now America’s beekeeping worry.
Varroa mites, also known as the “varroa destructor”, are proving to be a tough adversary for Maryland beekeepers. Here, knowledge is the first line of defense. Without recognizing the problem, many beekeepers could face hive losses due to these parasites. Unfortunately, this once included me: it wasn’t until after my hives had been hit that I was paying attention to the threat.
The whole experience left me feeling empty and inexperienced.
Dean Burroughs, president of the Lower Eastern Shore Beekeepers Association and beekeeping inspector for the entire DELMARVA peninsula who maintains 350 hives confirmed that:
Yes, your losses were due to Varroa mites and viruses caused by their invasion. Some 18 viruses have now been identified and there are probably more to be discovered. You need to test and treat as needed throughout the year to control the mite invasion.
The technique for counting varroa mites is explained in greater detail on the Walden Effect Blog.
In a Beekeeping 101 class this past summer, Michael Embry, University of Maryland Extension Apiculturalist, suggested monitoring for mites weekly from early spring through fall by counting fallen mites on a trapping board. As the number of mites increases, counting must occur daily and when the hive reaches 50 mites per inch or more, treatment is necessary.
Prevention and treatment options abound, but deciding the best for your hives merits some research.
The following suggestions include both natural and chemical treatments:
- To prevent mite infestation, Embry suggested a light dusting of powdered sugar on hives. When you apply powdered sugar to bees, they will “shake it off” and the mite goes with it.
- Among chemical alternatives is Thymol. Embry suggests Miteaway for use in summer months and Apiguard for use during winter months. Since Thymol is a thyme derivative, I decided to also try a planting a “fence” of thyme around my hives. Thyme blooms heavily in the summer, and the bees love it, so it was worth a shot!
Integrated pest management (IPM) is the practice of controlling honey bee pests with the minimal use of chemicals.
- Detecting Varroa Mites through the use of Drone Comb. Bee suppliers sell a special “drone” foundation that has larger hexagons imprinted in the sheet. The bees will only build drone comb on these sheets. That’s useful, because Varroa mites prefer drone brood over worker brood.
- By placing a frame of drone comb in each of your hives, you can “capture” and remove many mites. Once the drone cells are capped, remove the frame and place it overnight in your freezer. This will kill the drone brood and also the mites that have invaded the cells.
- Then, uncap the cells and place the frame (with the dead drone brood and dead mites back in the hive. The bees will clean it out (removing the dead drone brood and mites). The cells will get filled again, and you repeat the process.
Here are other resources to learn more:
Article from The Bee Informed Partnership:
Using Beekeeper’s Real‐World Experience to Solve Beekeepers’ Real‐World Problems
(source: American Entomologist, Summer 2012)
Image source: Agricultural Research Service, the research agency of the United States Department of Agriculture.