The Beekeeper’s Companion Since 1861
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The Classroom

The Classroom – July 2020

- July 1, 2020 - Jamie Ellis - (excerpt)

The Classroom - ABJ - Jamie Ellis
Q  Varroa and robbing screens

Do robbing/drifting screens help (or not) prevent Varroa transmission if you have them on every hive in your apiary and if so how much? I know you can prevent your bees from robbing out unprotected hives but is this a viable strategy to reduce the transmission rate of Varroa?

Cliff Stevens


Thanks for the question Cliff. For the benefit of the reader, I will note that your question is being asked under the premise that Varroa are spread, among other ways, by colonies robbing one another. Thus, you are essentially asking if we can suppress this method of spread by limiting robbing using robbing screens. I have a few thoughts about this.

First, I think we need to be quicker to spot failing colonies, work to remedy the problem faster, or cull them from the herd before they cause a problem for other colonies. I agree that limiting robbing and drift could help, at least theoretically. I also agree that this idea needs to be studied further. I would not be surprised, in fact, if it were being investigated, given the attention paid to “Varroa bombs” these days. [Readers: A “Varroa bomb” is a colony that is dying to Varroa and serving as a source of Varroa infestations for nearby colonies. Picture a bomb going off (the dying colony), spreading Varroa everywhere in your apiary.]

I have some experience with research on mite spread between colonies. Some years ago, I had two German colleagues (Drs. Niko and Gudrun Koeniger) visit my laboratory a few FL winters in a row. It was easier for them to get the jump on their research projects in FL while waiting out the German winters. During that time, they developed and tested the Varroa Gate. They had hypothesized that it would work by limiting Varroa movement into the hive from robbing bees, drifting bees, etc. They also believed it could treat a colony for mites. It did end up working as a colony treatment for Varroa, though it is not available in the U.S. I suspect some of its efficacy had to do with limiting the invasion of mites from outside the hive. Ultimately, I do feel that limiting robbing and/or drift could lower Varroa populations in a hive. I do not have experience with robbing screens specifically, but I feel that they likely help reduce Varroa spread, even if only a little. This topic needs to be investigated further.

Q  Winter losses

I have been keeping bees for over 30 years here in northern Vermont, and while my apiary is very small (never more than six hives), my hives have generally been quite successful. I have experienced some winter losses which has become pretty normal in my part of the world, but this year the losses were devastating as I lost my last three hives.

Normally, I can find the causes of past winter losses, but this year the hive conditions that I found have left me totally baffled. I usually winter my hives with two deeps and a shallow super. I put winter patties between the top deep and the shallow super as insurance as some years the bees will consume their winter stores early leading to starvation later in the winter. For the past three years, I have wrapped my hives with Bee Cozy’s instead of the tar paper that I used in the past. I treat for mites in the spring and in the fall, so I do not think that has been much of a problem. In any case, all three hives went into the winter extraordinarily strong; better in fact than in past years, so I was shocked to find all three hives still full of the same amount of bees as in the fall, but all were dead. In all cases, the bees were confined to about three frames wide against an outside wall, top to bottom and front to back of both hive bodies and the super. There seemed to be a lot of moisture in all the hives. There were very few bees on the bottom board. It almost feels like they died very early in the winter which was not as severe this year as in past years. I have never seen anything like this before. What do you think?

My second question has to do with hive configuration. This year I am planning to start one hive with all medium depth supers, basically as an experiment as the deeps have started to take their toll on this old back. I will be installing a three-pound package in the hive, and am unsure as to whether I should use two mediums to start or only one until they have drawn out all of the frames. A single medium just seems like too little space for three pounds of bees. Any suggestions?

Rick Warner
Vermont, April


I am sorry to hear about the loss of your colonies. I hate to beat a dead horse, but my default answer to mystery deaths is almost always Varroa. I know you said you treated your hives in fall. However, did you sample Varroa before and after treatment to see if the treatment worked? Also, treating in fall may have been too late. Keep in mind that the “winter bees” are produced in summer. Thus, you really have to have a handle on the Varroa populations well before fall to ensure that their impacts do not raise their ugly heads later.

Also, you can get bees starving in winter even when food is available in the hive. In these instances, you can get alternating warm and cold spells. During the warm spells, the cluster expands, they eat nearby food, etc. When it gets cold again, they contract, leaving a rim of honey-less comb right around the cluster. If it stays very cold for a while after that, they can starve with food all around them. In your case, you noted that they moved to one side of the hive, meaning they likely had little access to food horizontally at that point, even if they had a lot above them.

A third option could be ventilation. You noted a lot of moisture in the hive, which could be indicative of a lack of ventilation. This can be a problem for colonies that are overwintering.

My fourth option is a bit of the “catch all” option, where it could be pathogen related (Nosema, viruses, etc.). Unfortunately, once everything is dead, it is hard to tell.

For your second question, I have known a few beekeepers who switched to using exclusively mediums for their hives. They typically use two mediums as the minimum size hive configuration. I do not think it will hurt to start with one. However, I suspect that they will outgrow it very quickly … so why not just start with two?

Q  Crowded hives

In one of my apiaries, I had a recent instance of atypical swarming behavior with a large overcrowded colony during the peak of reproductive swarm season. This hive is located by itself with no other known colonies within at least a half mile. In this instance, I had done a reverse split exactly three weeks prior with removal of the old marked queen followed by culling of surplus queen cells five days later. There was now a soccer ball sized swarm atop the parent hive with an unmarked queen, acting very defensively. A quick inspection inside the hive revealed the frames packed with adult bees, a few opened queen cells, and (not surprisingly) no eggs. At the time I could not locate the swarm queen so I simply shook the bees out in front of another colony, thinking they had bearded and not found a way to re-enter the crowded hive. A week later, I found this swarm on the ground, still outside the hive where I had shaken them — with a small unmarked queen. I am wondering if these bees had simply exited the overcrowded hive and clustered around a recently emerged virgin queen who had managed to escape her rivals alive.

Crystal Lehmanking
Maryland, April


My ultimate guess with your question is that your colony tried to swarm with a virgin queen that could not fly. I see this happen from time to time. I most often see it with my old queens or queens I clip. In this case, the colony tries to swarm with the queen they have. Once the queen leaves the hive, she tries to take to the air, but ends up hitting the ground outside of the hive given she cannot fly. The bees either cluster on her there, or wherever she walks after hitting the ground. I routinely see the queens crawl underneath the bottom board of the hive, with the bees clustering around her there. She also may crawl to the outside of the hive and the bees cluster around her at that location as well.

Usually, if you catch these swarms and put them back into their hive, they will try to swarm again the next day, with the same results. The reason she does not go back into the hive on her own is because, in “her mind,” she has swarmed and the swarm is in the process of trying to find a new nest site. Once found, they may even try to fly there, with the queen, again, hitting the ground to be clustered around by her swarm. This happens over and over until the queen dies/is killed/disappears/etc. At that point, the swarm may recombine with its original hive or another hive in the apiary. I would not call this an atypical swarm, but rather an unsuccessful one due to the inability of the queen to fly. My guess is that a couple of virgin queens emerged in your hive at the same time, and one left with a swarm but was unable to fly for whatever reason (which can happen — perhaps she was maimed in a fight with another queen, perhaps she had other issues).

Q  What happened to our colonies?

We have purchased 16 hives and were being mentored since June 2019. But since the winter, we have been on our own as new beekeepers. The hives were doing extremely well. Someone told us not to reverse the lower and upper deeps in the spring, so we did not do this. We have had so many swarms, sometimes four a day. We spend all our time trying to catch bees, creating nucs, feeding nucs, etc. So today, we decided to look into the hives to prevent this incessant swarming and discovered the following pattern in most of the hives: old capped brood, lots of drones and drone cells, and several swarming queen cells. We destroyed all but one queen cup and destroyed most drone cells. We rarely saw any fresh eggs or larvae. We reversed the lower deep. The supers have some honey and some of the honey is being capped.

We figured our mistake was not reversing the deeps. We assumed the queen ran out of space to lay eggs, so she swarmed. We are counting on the lone queen cup left in each hive to …