Our guest author, Kurt Runzheimer, shares his novel method of varroa control using what he calls "Brood Annihilation".
My name is Kurt Runzheimer and I have been keeping bees in south central Wisconsin for over 25 years. I manage bees in 13 different locations in the Madison area. I have been using Trevorâs virgin queen rearing method with great success for a few years now. He and I often discuss our methods of managing honey bees and he asked me to share a technique I am working with to manage varroa.
As a former organic farmer and current organic gardener, I would love to say I have always been treatment free. Unfortunately, through the years I havenât been able to avoid treatments without massive die-offs due to varroa. As a result, I use oxalic acid vaporization quite effectively when necessary with the goal of working toward a decreasing need for it.
Brood Annihilation
I like to call the technique that I am working with âbrood annihilation.â I like this term because it literally involves a decisive destruction of all the developing brood of specific ages in the entire hive at once. There are 2 variations of the technique that I will share: one that uses oxalic acid vaporization (Variation OA), and one that is chemical-free (Variation CF). I have not used the oxalic acid dribble method, so I wonât include it here. Realize that everything I discuss is a work in progress. I most often use this on my large honey-producing colonies as the honey flow is ending. I included a few comments about timing at the end of the article.
The origin story...
One of the big challenges with varroa management is how to get rid of the reproducing mites in the brood nest. For organic chemicals, that job falls solely on the shoulders of
formic acid. In the past, I ran tests of Formic Pro for NOD Global during its development, without much success. I still saw massive varroa infestations and more queen mortality than I wanted. I needed a new way of doing things. I started isolating the queens to allow all the brood to emerge to give the colony a âbrood breakâ and then treating the hive with OA when there was no longer any brood. It seemed like waiting 24 days for all of the brood to emerge was an eternity. It meant I had to check very carefully for queen cells, and put my entire faith in the OA vaporization to follow. I also wondered about the risks for a queen to go so long without laying. I then started isolating the queen so she could lay on just a few frames, removing them when they were capped, and then freezing those frames to destroy brood and mites.
As I was working with different permutations of isolating the queen, it finally hit me: if I want to get rid of the reproducing mites quickly and effectively, why not just annihilate the whole brood nest? I would instantly have a broodless colony, have killed all the reproducing mites, and have only phoretic mites to deal with. Any colony could immediately have a brood break with only phoretic mites left in the hive.
This all has led to the development of the technique of brood annihilation I will describe below. As I mentioned above, I will present 2 variations. âVariation OAâ involves using oxalic acid vaporization to kill phoretic mites. âVariation CFâ is a chemical-free method that uses only brood annihilation to kill all the mites, including phoretic mites.
I ran tests of Formic Pro for NOD Global during its development, without much success. I still saw massive varroa infestations and more queen mortality than I wanted.
Variation OA (Oxalic Acid) Method
Materials to have ready:
- Brick or stone for pounding frames on.
- Queen holding cage.
- Serrated uncapping knife, preferably with a curved tip. The curved tip allows for more versatility cutting uneven comb. I am very happy with the Jero brand knife I have.
- Large tray on which to remove the brood.
- Running hose with a gentle shower nozzle.
In this variation, we will have only one brood annihilation of all of the brood age day 6 and older. We will leave all brood 5 days old and younger unharmed. After doing so, we will have destroyed 16 days of worker brood and the oldest brood left in the hive will be day 5 larvae. This means we have a 3-4 day window before there is any brood old enough to harbor mites at day 9. We will say it is a 3 day period just to play it safe. This is the precious window when we can medicate with OA to destroy phoretic mite
Step 1: The âpoundingâ step. Place your tray on the ground with a heavy rock or brick at one end of the tray. You will now go through the brood nest and remove each brood frame one at a time. With each frame you remove, first check very carefully for the queen. When you find her, cage her and put her in a shady, safe place out of the way. After checking for the queen, brush or shake the bees off the frame back into the hive. I always do this very gently until I have the queen in her cage in case I have missed her.
With each frame, cut open all of the capped brood on both sides of the frame with the serrated uncapping knife. Cut as shallowly as possible, so as not to damage the comb. Cradle the frame in your hands in such a way that your fingers support the underside of the comb (see PHOTO 1). Pound one of the wooden ends (side bars) of the frame a few times on the brick just strongly enough to loosen the brood to leave the comb (see PHOTO 2). This should knock the majority of the brood out of the comb onto the tray while the support from your fingers prevents damaging the comb. Rotate the frame 180 degrees with the same side facing down and pound again a few times. Turn the frame over and do the same pounding, with the same 180
degree rotation, for the other side of the comb. At this point, you will probably notice that almost all of the brood that is roughly 13 days old or older has come out of the comb, but a significant amount that is younger has not. You will notice that almost no brood that we wish to keep (day 5 and younger, including eggs) has even been affected. The remaining brood that we wish to destroy that did not come out with pounding will be dealt with in the second step. Take a moment to look at the hundreds or thousands of mites that may have been pounded out of the brood onto your tray (PHOTO 3). This is a great photo op. The brood can be composted or fed to the chickens.
Step 2: The ârinsingâ step. Take the frame over to the running hose. A gentle shower nozzle is important so you do not damage the comb. Place one end of the comb on the ground or some other solid surface. It is easiest if the side that you are rinsing is somewhat angled down toward the ground (see PHOTO 4). Carefully rinse all brood that is day 6 and older out of the comb on each side. Leave day 5 larvae and younger, including the eggs. Try to avoid getting water into the cells of the younger brood we wish to keep. You will find that it is quite easy to be very precise with the shower rinsing if you keep the nozzle close to the brood, perhaps only 0.5-2 inches away. It may take turning the frame to different angles and/or changing the angle of the nozzle. Continue until each frame is cleaned out of all brood that is day 6 or older. Once you are satisfied that you have gotten as much brood rinsed out as possible, grab the frame by the side bars and firmly shake out as much of the water as possible. Turn the frame over and repeat this on the other side. Almost all of the water will shake out, but what is left will be happily used by the bees. At this point, the hive can be put back together and the queen released. I like to put the frames with the remaining young brood together in the center of the lowest box or boxes. Pollen frames can go to the outside of the brood and honey frames can go on the very outside or top of the hive. You will find that there are always a small amount of cells that just donât get rinsed out of their brood. Donât worry, as this is a very insignificant amount.
Step 3: Killing phoretic mites with OA. We will now take advantage of our 3-day window to kill phoretic mites with OA vaporization. Remember, we want as many of the bees inside the hive as possible, as that is where they get exposed to the OA vapors. On the day after brood annihilation, return to the hive either very early in the morning or late in the evening when all the bees are in the hive. This may be as early as 5 a.m. if the temperatures are warm, or as late as 10 pm. I prefer morning, as bearding can keep large numbers of bees out of the hive on hot summer nights. Give the hive a full dose of OA vaporization as you normally do. Return 2 days later and do the same thing. This will give the bees 2 full doses of OA during our 3-day broodless window. At this point, the hive should be virtually mite free and ready to raise a new generation of healthy bees.
Variation CF (Chemical Free) Method
Before we begin, keep in mind that the essence of what we are trying to accomplish is simple. At the foundational level, each time we annihilate brood we are trying to accomplish three things. First, annihilate all of the brood of a certain age range. Second, leave all of the other brood unharmed. Third, put the hive back together in such a way that it sets us up for the next step.
In this variation, we will use three consecutive rounds of brood annihilation. It is more complex and requires very careful attention to details and deadlines. Round 1 will destroy all of the reproducing mites in the brood nest. Rounds 2 and 3 will capture and destroy as many of the phoretic mites as possible. In variation OA, we use the vaporization to âimmediatelyâ kill all the phoretic mites. However, in Variation CF we need to trap the phoretic mites in two successive maturations of capped brood.
***With careful study of the varroa life cycle from multiple sources, the vast majority of mites stay phoretic for 4-14 days, with about 6 days being the average. So, if we can allow 15 additional days of brood to mature until it is capped, we can capture the vast majority of the phoretic mites as they enter this brood and destroy them. We will annihilate these additional 15 days of capped brood in rounds 2 and 3. In setting up round 2 and 3, it is important to make sure that none of the capped brood reaches 21 days of age and results in emerging bees and fertile female mites. In total, Variation CF destroys 26 consecutive days of brood.
I will re-explain the techniques I like to call âpoundingâ and ârinsingâ in this variation, as the finer points are slightly different in this technique. This variation also includes the use of a queen excluder to systematically separate the brood nest and isolate the queen to one half of the brood nest.
Step 1: Killing the reproducing mites with the first round of brood annihilation. In the first round of brood annihilation, we will be destroying all of the capped brood (day 10-21) and preserving all of the uncapped brood (day 1-9). The 9 days of preserved, uncapped brood will become the first 9 of the 15 days of brood that will capture phoretic mites in the second round later.
To begin, place your tray on the ground with a heavy rock or brick at one end of the tray. You will now go through the brood nest and remove each brood frame one at a time. With each frame you remove, first check very carefully for the queen. When you find her, cage her and put her in a shady, safe place out of the way. After checking for the queen, brush or shake the bees off the frame back into the hive. Until I have the queen in her cage, I always do this very gently in case I have missed her.
The challenge we run into in this step is that the frames have varying combinations of capped and uncapped brood. For simplicity, we will classify each frame as we remove it into one of three groups: A, B, or C. GROUP A frames will be frames that contain ONLY uncapped brood and no capped brood. GROUP B frames will be frames that contain ONLY capped brood and no uncapped brood. GROUP C will be MIXED frames that contain BOTH capped and uncapped brood.
If the frame you removed belongs to GROUP A, it has ONLY uncapped brood. Set it aside. It needs no extra work. When we reassemble the hive, the frames from GROUP A will be put back in the hive ABOVE the excluder.
If the frame you removed belongs to GROUP B, it has ONLY capped brood. Proceed as follows: uncap both sides of the frame using a serrated uncapping knife. Cradling the frame in such a way that your fingers support the underside of the comb (see PHOTO 1), pound one of the wooden ends (side bars) of the frame a few times on the brick just strongly enough to loosen the brood to leave the comb (see PHOTO 2). This should knock the majority of the brood out of the comb onto the tray, while the support from your fingers prevents damaging the comb. Rotate the frame 180 degrees with the same side facing down and pound again a few times. Turn the frame over and do the same pounding, with the same 180 degree rotation, for the other side of the comb. Most of the brood will come out of the comb onto the tray. Take a moment to look at the hundreds or thousands of mites that may have been pounded out of the brood onto your tray (PHOTO 3). This is a great photo op. The brood can be composted or fed to the chickens.
Take the frame over to the running hose. A gentle shower nozzle is important so you do not damage the comb. Place one end of the comb on the ground or some other elevated surface. It is easiest if the side that you are rinsing is somewhat angled down toward the ground (see PHOTO 4). Carefully rinse all of the brood that you uncapped out of the comb. You will find that it is quite easy to be very precise with the shower rinsing if you keep the nozzle close to the brood, perhaps only 0.5-2 inches away. It may take turning the frame to different angles and/or changing the angle of the nozzle. Once you are satisfied that you have gotten as much of the brood rinsed out as possible, grab the frame by the side bars and firmly shake out as much of the water as possible. Turn the frame over and repeat this on the other side. Almost all of the water will shake out, but what is left will be happily used by the bees. When we reassemble the hive, the frames from GROUP B will be put back in the hive BELOW the excluder.
If the frame you removed belongs to GROUP C, it contains a MIXTURE of capped and uncapped brood. For GROUP C, we want to destroy the capped brood, but leave the uncapped brood unharmed. Proceed as follows: uncap all of the capped brood on both sides of the frame, using the serrated knife. For GROUP C, DONâT pound the frame, as this will damage the uncapped brood we wish to keep unharmed.
Take the frame over to the running hose. Using the same careful rinsing technique described with GROUP B, carefully rinse all of the brood that you uncapped out of the comb, leaving unharmed the younger brood that you did not uncap. Once you are satisfied that you have gotten as much of the correct age brood rinsed out as possible, grab the frame by the side bars and firmly shake out as much of the water as possible. Turn the frame over and repeat this on the other side. Almost all of the water will shake out, but what is left will be happily used by the bees. When we assemble the hive, we will need to use our discretion as to whether a given frame from GROUP C goes above or below the excluder. This decision making process is described next.
Step 2: Reassembling the hive after the first brood annihilation. Now it is time to reassemble the hive. Remember from above: the final result of this step will be to have a hive with a queen excluder separating the brood nest into 2 halves. The lower half below the excluder will contain the queen, as much empty comb space as possible, and as little developing brood as possible. The upper half above the excluder will contain as much developing brood as possible, and as little empty comb space as possible. The reason we want as much empty comb space as possible below the excluder is so that the queen has lots of room to lay eggs over the next 9 days before we return to the hive. The brood she lays below the excluder will ultimately become the third round of brood that we will annihilate. The unharmed developing brood that we isolate above the excluder will mature into only capped brood that will capture phoretic mites that we will destroy in the second round of brood annihilation when we return in 9 days. However, this is a slightly imperfect process, due to the GROUP C mixed frames. Some of the unharmed brood from these frames will end up below the excluder. It is not a problem, as you will see in the second annihilation.
All frames from GROUP B will go below the excluder, as they contain only rinsed out brood cells. All of the frames from GROUP A will go above the excluder, as they contain only unharmed, developing brood. The frames from GROUP C will now need to be placed with discretion. Because we want as much space for the queen to lay as possible, fill the rest of the lower box with the frames from GROUP C that have as much open space as possible. Once again, donât worry if they contain some developing brood. The frames from GROUP C that contain the most brood and least amount of empty space go above the excluder. Remember that this is an imperfect process. The key, again, is that the queen is isolated with a large amount of empty space to lay in for the next 9 days. Donât forget to release the queen below the excluder!
Step 3: The second brood annihilation. Nine days after the first brood annihilation, return to the hive. Remember, the queen is below the excluder. The frames above the excluder will now contain only capped brood. Letâs call these frames GROUP D. (These were the frames from GROUP A or GROUP C in the first annihilation). Perform the pounding and rinsing out of all the capped brood on these GROUP D frames. In doing so, we will have destroyed the first 9 days of phoretic mites by capturing them in the capped brood. Perhaps take a photo of the pounded-out brood.
Some of the frames below the excluder will contain ONLY uncapped, developing larvae and no capped brood. Letâs call these frames GROUP E. (These were the frames from GROUP B in the first annihilation). We will want to keep all of this new, developing brood on GROUP E frames unharmed and move it above the excluder. There it will mature and capture our final 6 days of phoretic mites. Set it aside for now.
Some of the frames below the excluder will contain a mixture of capped brood and uncapped larvae. Letâs call these frames GROUP F. (These were from the GROUP C frames from the first annihilation). Any capped brood on these GROUP F frames should be uncapped and rinsed out carefully while keeping the new developing larvae unharmed. DONâT do any pounding of these frames. These frames will go above the excluder where the brood will mature and capture our final 6 days of phoretic mites.
Step 4: Reassembling the hive after the second annihilation. The goal of this reassembly is to put the queen below the excluder with the empty, rinsed-out brood frames and no developing brood, and to put all of the unharmed brood above the excluder. The developing brood above the excluder will become the capped brood for our third round of annihilation. The empty frames below the excluder with the queen will now be laid with a new batch of winter bees!
To reassemble the hive, put the queen and all of the frames from GROUP D below the excluder. There should now be a large amount of open space for the queen to begin laying winter brood.* Remember, these should contain NO brood at all on any frames below the excluder. The frames from GROUP E and GROUP F contain all of the unharmed developing brood. They should ALL go above the excluder. In this reassembly, there will be no mixed frames below the excluder.
* When putting GROUP D frames below the excluder, make sure there is ample space for the queen to lay. Sometimes it may seem necessary to substitute an empty frame or 2 from storage equipment for one or 2 of the frames that are in GROUP D if they have become overcrowded with pollen or honey.
Step 5: The third annihilation. Return to the hive in 6 days. Remember the queen is below the excluder. Our goal for the last annihilation is to destroy 6 more days of capped brood. Combined with the nine days from round 2, that will give us a total of 15 consecutive days of capped brood to capture phoretic mites. In this step, the frames below the excluder will remain untouched. Remember that these frames are our new developing winter bees. Only the frames above the excluder will be dealt with. When you start to remove the frames of brood from the top box above the excluder, you will notice that not all of the brood is capped. That is because it has only been six days that the brood has been away from the queen. Two things are important here. First, the capped brood will be the six days of brood that we need to destroy. Second, the uncapped brood can be preserved so that it will be free to develop into the hiveâs first new winter bees.
When annihilating this third round, you will want to be careful so as not to destroy the uncapped larvae. DONâT do any pounding in this step, only rinsing. Remove a frame. First, with your serrated knife, uncap the capped brood on both sides of each frame. Then carefully and precisely rinse out all brood that you cut open, but leave the other developing larvae unharmed. Once you have finished, shake out the water on both sides of the frame. Repeat with all frames above the excluder.
Step 6: Reassembling the hive after the third annihilation. Remove the excluder, and put the frames back into the box, or boxes, they came from. These boxes are still on top of the box with the queen, but there is no longer an excluder. The queen will now be free to lay where she pleases and build the hive up for winter.
Timing of these methods is key to being successful during the winter
It is important not to wait too late into summer to do this brood annihilation protocol. If you wait until late August or September, the bees wonât be able to build up quickly enough to repopulate for winter, and may already be suffering from varroosis. Lately, I even think mid August is too late. Iâve found that late July (Variation CF) or the first week of August (Variation OA) is a good time.
For Variation OA, I recommend removing honey supers immediately when the honey flow ends and then right away doing the annihilation. This way, the hive will be much smaller in volume and thus the OA vaporization will be more effective. In Madison, the honey flow ends the last week of July, so I remove the honey supers immediately and begin Variation OA annihilations. By the time I am done with these, my rural hives are ready for the treatment. This is usually one week later.
For the Variation CF, there is a longer period of brood destruction, so the hive will take longer to build back up. For this reason, itâs a good idea to start at the end of July. Also, having honey supers on wonât be a problem when you start. Because you wonât be vaporizing, you donât need the smaller space immediately.
Consolidating the cavity size for winter
As August comes, the hive population naturally starts declining. Combine that with the fact that we are annihilating many thousands of developing bees, the hive will show major population loss as we head to September. Thus, brood annihilation is an excellent time to think about reducing the size of the hive with winter in mind. I would definitely recommend closing the main entrance to just a small 1-2 inch opening to prevent robbing and mite migration. â inch hardware cloth can be used to keep the bottom entrance ventilated if that is desired.
For Variation OA, I mentioned that it is nice to remove the honey supers just before (or the same day) as brood annihilation. This reduces the hive down in size so that the OA vaporization can be more effective. HOWEVER, if you reduce the hive down any further at this point, you will find the potential for a massive amount of bees to hang out outside the hive. These bees will no longer be susceptible to OA. So, I would recommend finishing the two OA treatments before reducing the hive any more for winter.
For Variation CF, you can begin brood annihilation before the honey supers are off. This is because we donât need to immediately reduce hive space since we are not vaporizing with OA. You can remove honey supers as you see fit. I would recommend waiting until the third annihilation, or shortly thereafter, to reduce the hive significantly. Because there will be 26 days of brood loss, I would recommend using 5 frame equipment for winter.
Kurt Runzheimer of City Bee, Country Bee Apiaries cares for hives throughout Madison and rural Dane County, including at Olbrich Botanical Gardens. Kurt has been a beekeeper for more than 25 years and enjoys sharing his experience with people of all ages, from kids to seniors. Much of his work is mentoring individual or small groups of clients through the yearly cycle of beekeeping. He specializes in the art of âsingle sourceâ honeys from specific floral sources, unique locations, and distinct times of the year. His favorite is goldenrod honey. You can contact Kurt via email kurt.runzheimer@me.com
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