Varroa mites first became a threat to Australia. Recently, an Australian ABC news station reported, “Varroa mites discovered on a 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 that 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.
Varroa Mites are external parasites that feed off of honey bees, especially drones. They feed off the bees ultimately weakening and harming them thus, shortening the bees life. The mites also feed off the brood, the bee larvae. This can result in deformed adult bees missing wings or legs. Varroa Mites can kill off an entire colony of bees if they are not properly treated by the middle of the honeybee season.
I think of Varroa Mites as bee ticks.
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 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. Mike later told me that the sugar had a negative impact on egg production and told me that this probably isn’t a great idea.
- Among chemical alternatives is Thymol, a thyme derivative. 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 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.
Treating Varroa mites
I am a slow learner. I was always really against using any sort of chemical treatments in the hives until I decided to learn more about what each treatment does for the bees and their health. Mites are the issue. So, they need to be eradicated.
In a conversation with the man that I buy my bees from in early-July this year, he said to me, “Get your mite-away strips on by mid-August” I said, “I usually do that around the end of October”. He replied, “If you wait until the end of October, then I will see you again in April for new bees”.
A light went off.
I ordered the mite-away strips and we treated the bees in August, We now do this treatment in June after the first honey harvest. Mite-away Quick Strips are made with Formic Acid. Formic acid is a compound that is naturally found in the hive and is the bi-product of insect bites and stings. It’s proven to be effective against varroa mites. This product should not be used in temperatures over 85 degrees and the treatment stays in the hive for only 5 days.
We were lucky this August; it’s usually very hot here in the south. We had 5 days that were about 82 degrees and the process seemed to work. We saw lots and lots of dead varroa mites after the treatment. Don’t ask me to count. I can’t even keep pace with our inventory. The thought of sitting in the bee yard and counting tiny black dots on a whiteboard late in the day– it’s just not going to happen.
The next step in treating the bees involves vaporizing oxalic acid. Oxalic acid is an organic compound in leafy greens. We started mid-September. We are now treating in August. The way it works is to treat every 5-7 days or as our schedules permit for three cycles.
Here is what I’ve learned about treating varroa mites with a vaporizer:
- Get your Oxalic acid from a reputable source.
- Don’t buy a vaporizer that looks like this one below. Find a professional one made by a company with an integrated timer.
- Buy 2 units if you can swing it, it will save you enough time to justify the cost
- Drive to your hive in a vehicle that has an easy-to-access battery
Treating Varroa Mites Step 1:
Measure 1/2 teaspoon of Oxalic acid crystals, drop into the vaporizer, connect to a car battery and set your stop-watch to see how long it takes to dissipate from the unit. That is your burn time. (You cannot see what’s happening when you insert the unit in the hive). In my case, it was for 5 minutes.
Since the writing of this blog, we’ve invested in a very good, very reliable, professionally made vaporizer that has the timing aspect built into it. Buying this handmade unit shown in these photos was unreliable. I have to thank whoever helped themselves to our units, the replacements are far better and now kept under lock and key.
Treating Varroa Mites Step 2:
Slip the unit into the hive through the entrance. Cover the entrance with a towel. Covering the entrance with a rag is necessary for this step. You want to coat the bees in vapor. Cover any major openings with gloves or paper towels.
Attach to the battery of a running vehicle and time the treatment. In my case, I set my stopwatch on my iPhone for 5 minutes.
Treating Varroa Mites Step 3:
Remove the towel from the hive and remove the unit from the hive.
Step 4: Allow the unit to cool.
Think: What happens to wood when it gets too hot?
Step 5: Move to the next hive
Here are other resources to learn more:
- Bee Informed Partnership website
- Maryland State Beekeepers Association, Inc.
- Barefoot Beekeeper
- How to diagnose
- Honey Bee Disease
- 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.