postmortems & mysteries

Colony postmortem #4: two losses in one week

Here’s a new postmortem for all of you bee sleuths out there. Jim Metrailer from Alabama sent the following pictures and questions with the go-ahead to share them with you.

The first colony

On January 25th, a sunny day with temperatures in the mid-50s, Jim inspected his hives. His top-bar hive and one Langstroth showed activity, but the other Langstroth was completely inactive, showing no signs of life.

Here you can see a few bees on the bottom screen interspersed with a few small hive beetles.
Here you can see a few bees on the bottom screen interspersed with a few small hive beetles. All photos by Jim Metrailer.

Upon opening the hive, he found no bees in the honey super which was situated above a queen excluder. The super itself was well-stocked with honey.

In the brood box below, he found the marked queen, torpid and alone. A few dead bees had accumulated on the bottom screen along with some small hive beetles. The brood box contained lots of honey and pollen. The nest contained capped brood, eggs, and larvae, and a small amount of feces was visible on the frames.

A small amount of feces was visible on the frames.
A small amount of feces was visible on the frames.
Shot brood can result from several different conditions.
Shot brood can result from several different conditions.
This photo shows dead and darkened larvae, some eggs, and the remaining capped brood.
This photo shows dead and darkened larvae, some eggs, and the remaining capped brood.

Jim noted that the bees in this hive were fed Honey-B-Healthy in their fall syrup, and that back in June this hive had a large number of dead bees in front of it.

Jim’s questions

  1. Could this situation be caused by Nosema apis? He theorized that the pathogen could have reduced the population to the point where the colony could no longer keep itself warm in winter.
  2. Should the dead bees be examined for Nosema?
  3. How might the brood box frames, honey, and residual brood be used?
  4. How should the equipment, the box itself, and the bottom board be handled?
  5. How can the honey frames in the super above the queen excluder be utilized?
  6. Any other thoughts or suggestions?

The second colony

Then, on January 31, I received an update from Jim. The second Langstroth was now showing no sign of activity and, upon opening, no bees were present. The hive still contained plenty of honey. On a side note, the top-bar hive was still showing lots of activity.

Jim’s new question is, “What did I do wrong?”

At this point I was able to gather a bit more information:

Neither of the dead colonies were treated for varroa because mite counts had shown an infestation rate of less than 1%. The second colony to die was also supposed to be varroa-resistant. Jim uncapped some of the brood and found no varroa. These colonies were both quite populous in the autumn.

The top-bar hive in this same location was also not treated. Jim also has two top-bar hives in another location that are doing fine. One, started from a package, was treated with Apivar, and the other, started from a swarm, was not.

My thoughts and observations

I suppose this set of conditions could be caused by one of the Nosema pathogens, although in lots of areas N. ceranae has replaced N. apis, so I think the former is more likely. I think the small amount of feces shown in the photo is a red herring. It’s such a small amount that it could have been released by a bee with bad timing. Furthermore, although Nosema apis and dysentery often correlate, Nosema doesn’t cause dysentery. Even if the bees got into some watery feed, it sounds like they’ve had enough fly days to take care of it. I also think the number of small hive beetles is a non-issue.

Often, if the queen has Nosema, you see some queen cups in the remaining brood patch, which are obviously not here. Queen cups, though, are not mandatory.

The small number of bees on the bottom board suggest to me that, until recently, the undertaker bees were still carrying out the dead. Alternatively, the bees, knowing they were sick with something, were performing altruistic suicide, flying away to die remotely. Also, in my experience, the dead seem to pile up more with Nosema than they do with varroa—not sure if that’s a fact or not.

The shot brood photo is hard to read. Shot brood (a brood pattern that looks like it’s been hit with a shotgun) can arise from several things. It can result from an inbred queen, AFB, or varroa, and probably other conditions as well. I doubt it was an inbred queen because she was doing well until now.

Holes in the cappings

One thing I do see is some caps with holes that often arise along with varroa mites, but they also appear with AFB. I don’t see any additional signs of AFB, however, such as scales with tongues or dark cappings. It would be helpful to know if any odor accompanied the brood nest.

The close-up photo is pretty interesting. If I’m seeing any mite frass, it’s not predominant. The dead larvae are dark, which probably means they got chilled and died, which makes sense. The odd thing is the eggs. The eggs appear to be single, centered, and tipped over, which indicates they were laid by a queen and not laying workers. This queen appears to have remained active until just a day or two prior to the photos, and until recently she was still laying fertilized eggs.

Things that make me think of varroa are:

  1. Honey remaining in the hive
  2. Most bees are gone, a possible indication altruistic suicide
  3. A small patch of brood remains, accompanied by a queen until recently
  4. The collapse occurred in late winter
  5. These were large colonies going into fall (large populations tend to collapse faster from varroa than small ones)
  6. Although varroa numbers were low in fall, I don’t know the protocol for counting (sorry, I didn’t think t ask)

I don’t know the answer

In spite of all that, I don’t know the answer. I lean toward varroa, but that’s based just on the things I can see and not those I can’t, so I’m eager to see what everyone thinks. I know that Jim will appreciate any insight you have.

Honey Bee Suite


  • 4% is the number most commonly used when treating for Varroa Destructor mites. Sample a half cup of bees taken from the brood nest area (this is where the mites will concentrate because they want to lay eggs on the new larva before they are capped) and pour them into a container that is used to test for mites. The alcohol test is considered the most accurate (as opposed to the powdered sugar roll). Pour enough rubbing alcohol on them to cover the bees plus about 2 centimeters. Shake the bees for 2 minutes then pour them through an eighth inch screen onto a white surface. Commercially manufactured test kits contain 2 jars with a screen between them but the hobby beekeeper can make their own. The screen separates the bees from the mites. The mites should be counted and the number should be divided by 3 to get the percentage for 100 bees. If you have 4 mites you need to treat. Some say 3% for August and 2% for the spring seasons. Going into winter with mites is a serious thing. They usually don’t make the winter.

    You will never know what killed these bees but with the information you provided I would vote for Varroa.

    • Clifford, you should update your reading re varroa, specifically their reproductive timing. Also, Randy Oliver has some great info on DIY mite sampling devices and techniques.

  • Even though you don’t see all the classical signs of AFB, have you considered checking with a test kit? Given how devastating AFB is in an apiary, I would want to make 100% sure that wasn’t the cause. I am sorry you lost your bees.

  • Such a shame…my condolences to Jim. In the last few winters I had been puzzled by having big, robust colonies that I was sure were in good shape for winter suddenly die in the first cold snap (which for us in the PacNW is usually in November). No warning, just poof, and they are all dead on the bottom board, often with a small cluster dead on the frame, huddled together around the queen. Les Eccles gave a presentation to the BCHPA on how mites can, in spite of what seems low late season counts, overwhelm colonies in fall and early winter (as bee numbers fall naturally), causing this sudden death in the first bit of real cold. Your biggest boomer hives are usually the victims, because an artifact of their success is that they are mite factories. A few points to ponder:
    1. mite resistant does not mean mite-proof. You still have to be on the mites.
    2. we have, sadly, in our club seen many colonies bought specially as being some form of mite resistant, and none has performed as such in the field. One thing to ask your MR seller is: what metric do you use to measure that mite resistance? Note that freeze-kill tests are not a reliable measure of mite resistance.
    3. we used to wonder: are these winter kills Nosema ceranae (which is symptomless)? If effective mite control increases your winter survival rate, the problem was not Nosema but mite issues. This is what we are seeing locally this winter…more frequent mite control in summer and fall seems to be driving high survival rates (95%+).
    4. running Vita Life test kits can settle the question of whether foulbrood contributed to the hive demise. Given the odd looking brood (patchy, looking like larvae are dying before capping) I wonder about EFB. EFB rates rose in 2019, in many areas.
    5. were the colonies strong 10 frame colonies in fall, well fed esp with pollen? Big colonies can form big, warm clusters. How was the brood pattern in the late summer? That is the time to detect “issues”, when you have time to remediate.

    All things to think about in approaching the 2020 season. In our club we try to pair up beekeepers who have had a tough winter with experienced beekeepers whose colonies routinely do well in winter. There are a few points of practice/management that must be used in at least late summer/fall. It can be helpful to observe what successful beekeepers do; sometimes it is a small thing that can make a big difference.

  • I wish I knew. My last surviving colony died this week. I was hopeful that they were making it through a Michigan winter, but no luck. I have not been able to carry a colony through winter for at least 5 years. I wondered if it was time to throw in the towel, but decided one more time. This time I ordered two packages, Italian and saskatzaz which are supposed to be mite resistant. I have no answers, I wish I did. I hesitate to open a hive in February no matter I can’t hear them anymore but I suspect varroa even tho they were treated late summer. Whole thing feels bad.

  • Hi, we treated my hives for varroa in late August and all seemed fine. My brother did his as well. Then in November we decided to treat again with oxalate acid with sticky boards in place. We were stunned by the results. Some hives having as many as 1500 mite drop in the first 24 hours. We treated every 5 days times 3. By then it was too cold to do a mite check. We treated again x1 late December with minimal mite numbers. My brother treated one more time in January. I did not. So far our hives are doing well as far as we can tell with some of them booming. Again, we were really surprised by the mite bombs we had in November. I’m sure without the late treatments we would be looking at high losses. Time will tell if we caught it in time. I think we underestimate the varroa.

  • What did the entrance look like? If covered with feces or a lot on the ground in front of the entrance I would say it could be nosema.

    But nosema can also be a system of something else.

    There appeared to be a huge amount of debris below the screen.

    How cold was it the previous three or four days. If freezing the bees could have been in a tight cluster. The out side bees in the cluster could have died from exposure. The cluster could then have died from the cold and starvation. The cluster would have let brood die to protect the queen. That could be why the outer edge of larva was black.

    But I could be completely incorrect and the cause is varroa. Just throwing out ideas.

  • Although Jim doesn’t say what the temps were before and after the bees broke cluster to do cleansing flights, perhaps they couldn’t cluster back up and the brood chilled? or moisture was a problem? no top entrance?

  • This is what happened to me also. Had 15 hives and now down to 9 hives. Treated with a 2nd treatment of Apigard (25g) the end of August. Started feeding sugar water and pollen patty for a few weeks. Had seen the queen in October just before treating again 3 times every 5 days with oxalic vaporization in November. Then 1 more time in December. Then added Mountain Camp sugar. Upon inspection found they had honey and food stores (not a lot) but no brood. I found a queen barely moving in one of the hives that I had to put down, but the others just a handful of dead bees on the bottom screen. One of the dead outs had a ton of mites after treating with oxalic vaporization. I’m thinking viruses on that one but not sure what happened on the others. The dead outs happened at different locations. The other live hives are doing well.

  • “What did I do wrong?”

    It might be that Jim did nothing wrong.

    I hope he’ll give the comb and honey frames some time in a freezer in case of beetle or moth eggs, scrape out the boxes, and get bees back with those boxes come spring.

  • First hive.

    “Few” hive beetles … looks like a lot to me. But I guess, being in Alabama, it’s a little to them.

    The feces seems to be the wrong color for nosema. In my experience, Nosema is very dark, almost black. (I will send you a picture via email to show you what nosema looks like in a hive )

    There “IS” mite feces seen in some of the cells. Only one mite can infect a whole colony, especially in the winter. From what I see, he had mites. Thus he had virus.

    Large number of dead bees in June, during the main flow. NOT GOOD. Means colony was already infected or were poisoned in some way. I have seen with my own eyes infected colonies walk out by the thousands at one time just to die in the grass in a bunch. It’s too sad. Then rebound. Then die.

    In answer to his question re: what to do w/the frames, etc. I doubt it was Nosema as really, I don’t see any evidence of this (from my experience w/Nosema)

    He should spin the frames of honey. DO NOT FEED BACK TO THE BEES because he has no idea what they died from. If, in fact, it was Nosema, he will infect the other hives. BEEN THERE< DONE THAT ….. don't do it. Plus, one of the number one rules is … DO NOT FEED YOUR BEES HONEY FROM OTHER HIVES. Yes, if it's your apiary and you know them to be healthy is one thing, but to take frames from a dead out, well, that's another. You risk killing or infecting the other colonies doing this. Take the cautionary road.

    I would spin the honey and burn the frames. Not worth risking their spreading disease to other hives. Beekeepers infect hives daily moving frames around and putting in healthy hives. Frames are cheap.

    The boxes, scrape them out and burn the sides or clean thoroughly with a vinegar or bleach solution and then air out for a few weeks. Use one of them wire brushes so that you get every nick and cranny. Even a small amount of Nosema spores will infect the whole hive. BEEN THERE ! Virus will not leave the hive on it's own.


    Second hive.

    What method did he use to check for mites? Alcohol wash? Sugar shake? White board? Checked under cappings? Drone trapping?

    Varroa resistant? What is that? I haven't seen that at all …. all hives get mites. So they are marketed as "varroa resistant", They are NOT virus resistant !!!!!!!!!!! With over 28 varroa mite viruses to choose from. Mite resistant .. maybe, virus resistant .. absolutely not.

    This does not look like AFB to me. No sunken capped cells. The capped cells look healthy enough, but tiny varroa holes really do give it away. For AFB, from what I've seen, usually the cells are pretty much black and nasty. Don't see that here. I read somewhere, possibly the ABJ or Bee Culture, that the bees are learning to poke holes in the cappings because the varroa cannot reproduce if they get air into the cells. I do not know how true this is, maybe Rusty does. They do show some great pictures on one of the Bee websites, but I cannot remember which one. (If I can find it, I will f/w to Rusty)

    Mites don't have to be overwhelming to cause virus. It could be that it's a shotgun pattern because the bees removed any infected larvae, but then got too weak to do much more and all perished as evidenced by the dead bee larvae in the cells. Or, the bees in them cells emerged seeing as they were towards the middle of the cluster of cells because they were born earlier than the out lying cells. As you explained, the black larvae had died from exposure because there were not any bees to tend to them. The bees were dwindling and abandoned the brood as well as the queen. They just could not do it anymore in their infected state. Further, if the nurse bees were already infected they infected the larvae. Seems like they totally removed the cappings from the infected bees. (humm)

    I don't believe it was queen failure in any way. I believe the one hive had virus in June and possibly transmitted it from bee to bee (or robber bees) from hive to hive, taking the virus with them. The hive then 'rebounded' for fall, but virus was still in the hive and thus, the hive perished as the virus took hold of the new bees. If it was queen failure she would not have produced up to the end and been left alone in the hive when all others died off. I would have liked to see what this hive looked like in June, then again when it rebounded and then perished. I have seen varroa/virus infected hives rebound nicely only to perish when times got rough. If the new bees are infected, they really cannot do much.

    This happens all too often. You can treat 'after the fact' but the virus remains. Treatments get rid of the mites, but treatment does NOT take care of the virus.

    Here in Ohio, it's not worth testing for Nosema because they cannot determine if it is apis or ceranae. So why bother. See pictures I sent to Rusty of hives that had a bad case of Nosema. See how the feces is almost black and it's everywhere. The feces in the picture is the right color. I agree it was just a bee who was probably too weak to get outside and was on it's way out, thus it had to go in the hive. But it's not messy and all over the place, just a few droplets.

    I don't know what the weather is like where he lives, but if they got a cold snap, like they did a week or so back, it could have put this hive over the edge as it doesn't look like there were enough bees to do much of anything, much less take care of their broodnest. You see the little bees huddled in the corner and they perished there. I would be curious as to where the bees on the bottom board dropped. Did they drop right under these bees? Or did they drop further over the brood area? Where did the dead drop?

    Since the other hives are 'doing fine', it's still early in the season. Anything can happen between now and the Spring. These two months, Feb/March are times of peril for a lot of hives. A lot of hives die off during these months after surviving the winter harshness of January.

    As with any other living thing, some hives will be better at fighting virus than others. It would depend on the genes of the bees. Plus, the infected bees might not have gotten into the healthy hives or these bees did not 'rob out' or 'sneak in' the infected hives. Bees tend to transmit virus to other hives during the flow or during robbing a dead out.

    With bees, it's hard to tell about anything. One can only guess. It is very very expensive to have the bees checked and then most of the time, they have no answer and you've spent all this money and you still don't know what happened to your bees. Better to take this money and start over trying to do better next time around. Bees ARE NOT easy to keep alive.

    As a beekeeper, he possibly didn't do 'anything wrong', it's just how it is. All one can do is monitor their bees, treat when necessary and hope for the best. Even if one does everything right, the bees can still perish as we cannot be sure where they go and what they bring home. They could have even brought home a toxin and put it in the honey and bee bread that they fed to the larvae. It's a toss up.

    Even if one has 'marketed resistant bees', I would treat anyway if I saw mites. I would not trust the 'marketed resistant bees' to fight off such a mite/virus load. Further, these 'MRB's" cannot be duplicated. As the swarm queens mate, they lose their resistance because, from what I read, resistance is in the drones, not the queens. Thus, one would need a drone saturation area to be sure that your queens would be mated with any type of resistance. (I could be mistaken, but I think I remember this correctly.) People tend to market these bees to make money. (My bee is better than your bee)

    He should take care of the bees he has that are presumed 'healthy' and in the future, if he sees mites, he should treat. I would make sure the bees are well fed, kept warm and if necessary, treat for mites. Really, anymore, l% is too many mites in a huge hive. Virus Virus Virus As you can see, every year they lower the acceptable threshold.

    What did he do in June when all them bees were dead in front of the hive during a major flow? Did he go into the hive and look? What did he see then? Did he do anything at that time? So many questions.

    Hang in there Dude, as you will have good years and bad years. Some beekeepers quit immediately because they realize how difficult bees are to keep. Others hang in there and take their lumps. The less hives you have the better off your apiary will bee. If you keep adding hives until you have lots of them, then you risk infection more than having less hives. Crowded apiaries are know for disease transmission. You just cannot get away from it.

    Good Luck to you this year. Hang in there .. it only gets worse ! ha ha
    Sorry I wrote you a book Rusty, but you asked !!!!! (ha ha)

    • //As the swarm queens mate, they lose their resistance because, from what I read, resistance is in the drones, not the queens.//

      How does that work? It might be right, but it isn’t instantly obvious how.

      I thought the honey bee had a haplodiploid way of determining sex – that is, the males develop from unfertilised eggs and have only a half set of chromosomes. In which case, the drones don’t have any specific genes which aren’t potentially possessed by the queens and therefore passed on by them.

      Is it that resistance isn’t dominant and/or isn’t a common trait and so is more likely to be weakened rather than strengthened by uncontrolled mating?

      Would be interested to know… 🙂

  • PS: Randy Oliver has been writing about Nosema over the last six months in the ABJ. You might want to read his articles. Lots of new scientific info on Nosema. Don’t think it was Nosema at all.

  • The first thing I would ask is where in Alabama. It is not a huge state but does run from the Gulf Coast to the bottom edge of the Appalachian Mountains. There is some serious agriculture in some places and not so much in others, consequently exposure to ag-type chemicals could be high to non-existent.

    Secondly I would say the bees on the bottom board look like old bees, slick and very black and essentially hairless. At the time of year given there is plenty of food resources and little to no sign of varroa (and test by the beekeeper that suggest the same) I would guess nosema c. At least here it typically shows its ugly head beginning in the fall with the arrival of cold weather and typically by January the hive is unpopulated…. ie almost dead… there may the a handful of bees and sometimes the queen wandering around aimlessly. Nosema (of both types) does create the situation where the infected bees will fly at sub optimal temperature and die outside the hive.

    With Nosema c. (in my own experience) there is nothing you can do to correct the problem. Fumidil applied in the syrup in a bottle feeder will prop the hive but as soon as you quit feeding with Fumidil the hive will again begin to decline.

    Gene in Central Texas…

  • I had two similar die-outs last fall and I think it was varroa; I treated with folic acid but while on vacation. It was pretty hot around home – so it could’ve been that as well. My question for Jim – is it usual to leave the queen excluder on going into winter? Here in IL, a cold snap leaving the cluster above and the brood and queen below would surely have been a death sentence. I hope we all figure it out so we all can learn! Thanks Jim for sending in the mystery! ❤️?

    • Jill,

      I build my candy boards with a queen excluder on the bottom and have used that configuration for years, often with zero colony loss. The bees will not abandon the queen and her brood. Instead, the “retriever bees” go up, collect food, and bring it back down for the rest. The excluder should be another non-issue.

  • It’s varroa. It’s always varroa. I treated three times last year and it’s still varroa. (Also, maybe I have Seasonal Affective Disorder, but it’s still varroa.)

    PS: You said “Also, in my experience, the dead seem to pile up more with Nosema than they do with varroa—not sure if that’s a fact or not.”

    It’s probably a fact that this is your experience. I’m pretty sure I don’t have Nosema experience, but it’s a fact that tons of dead bees on the snow and then tons of dead bees on the bottom board at the post mortem goes along with my I’mPrettySureIt’sVarroa experience.

    Also, I need to treat and none of my available treatments are any good till the temperatures get higher. I’m gonna have to bite the bullet and learn/buy/do the messy/complicated/difficult Oxalic dribble or the EquipmentExpensive/I’llBurnTheBeeYardDown Oxalic vaporization. I know you write well of the dribble, but the vaporator sounds so easy (except for the respirator and the burning the bee yard down parts).

    • Roberta,

      Sorry, I meant pile up inside the hive, rather than outside the hive. It seems that varroa-collapsing colonies keep hauling out the dead until the last minute, whereas nosema-collapsing colonies perhaps don’t have the strength to haul them outside. But like, I said, it’s just an observation.

  • Sharon, Saskatraz bees ARE NOT mite resistant. Don’t be fooled. Ask the many people here in Ohio who have them. You still have to treat. They still get huge mite loads. Be careful of slick marketing. Varroa is winning, not the poor bees. It’s all in the genes. Great posting Rusty. Love these.

  • Hi Rusty,

    Question: those cappings don’t look normal to me… slightly sunken and discolored. when brood dies and stays capped, is this the normal appearance?


    • Isaac,

      With not enough bees to keep the brood warm, it would die of the cold, whether capped or uncapped. When that happens the partially developed bees turn dark and shrivel, which can make the cappings look different. A number of different conditions mention sunken and dark cappings, but it can happen any time the brood beneath is dead.

  • I would have to agree with you on this. As for the pile of bees in front of the colony in June; I have seen that when the beekeeper has taken honey and then a dearth hits, the bees will sacrifice themselves when they are starving and end up dying just outside of the colony in a pile. So, the stores are the first thing to check when there’s a pile out front, then pesticides, etc.

  • I’m in Alabama and the weather here has been totally insane this year. Temperature swings of forty degrees within a few hours have been common the past few months. It wouldn’t be too far fetched for the bees to have gone out for a cleansing flight and freeze to death before they could get back home. Today it was 62 F this morning. 50F at lunch and it will be below freezing by morning. And this was far from the most drastic swing we’ve had. I’d bet this weather was a factor in this. We all know that it doesn’t take a large loss to tip the scales and kill the colony, especially this time of year.

  • ‘Neither of the dead colonies were treated for varroa because mite counts had shown an infestation rate of less than 1%.’ Jim doesn’t say how he measured for varroa. I don’t imagine he did an alcohol wash in mid-winter.
    I have two hives which I treated with Apivar in August and I planned to dribble oxalic acid in December. (That’s a very common approach here in England.)

    But the mite counts (on a sticky board under an open mesh floor) in November were extremely low, so I hesitated about doing a mid-winter treatment. Then I read this:

    ‘Varroa counts before treating are only useful if they’re meaningful and I suspect they aren’t in midwinter. At this time of the year many colonies will have no brood, some will have some and a few might have more (but probably not lots). It’s all dependent upon the weather, the bees and the strength of the colony … and probably other things. In the absence of any brood the natural mite drop is influenced by how active the cluster is – on a warm winter day you often see more mites than on a really cold day when they’re clustered tightly.’ David Evans:

    So I dribbled oxalic acid after all. A few days later, there were 260 and 340 mites on the monitoring board.
    It makes sense to me that fewer (live) mites fall through the mesh floor on to the sticky board when they are tightly clustered.

    So, Jim, you might not rule out varroa just because you got low counts.

  • I think varroa must have played a part, to some degree or other. It is likely to be a number of issues, with varroa just being one of them. No one has mooted a poor queen – it doesn’t look like a very good pattern. Even if she was laying in the autumn she may have run out of steam in the intervening period. With few new over-wintering bees being born in late autumn the colony would have been doomed at some point over the winter.

  • From other’s observations:

    Pile of dead bees outside hive
    Black, hairless bees on bottom board.

    Sounds like the symptoms of Chronic Bee Paralysis Virus.

  • I think it was Varroa + viruses for whom Varroa is a vector. Also, giving bees Honey-B-Healthy is tricky — too much essential oil will disrupt their gut microbiome. In my opinion, Varroa is a symptom of a problem, and not a problem per se. Nowadays honey bees have low immunity (inbreeding, stress, environmental toxins, lack of nutritious food) and that opens the door to many issues. Personally, I have only been able to overwinter small or medium-sized colonies; sometimes with a little help, such as bringing them indoors when temperature is below 20 F for too long (we’re in Michigan).

  • This is all SO interesting. And way above my non-scientific, non-feeder, non-treater mind. What occurred to me from the first, simply, was why he opened his hive and exposed his brood in mid-50’s temperatures? Here in Sonoma Valley we wait until temps are in the mid-60’s before any major checks. Otherwise of course we risk chilled brood. That said, temperature does not answer the presence of feces. I think Isaac’s comment makes the most sense in solving just one of the mysteries of honeybees and why they fail in some seasons. And why they thrive in others. Many of us beekeepers in this part of our county lost our hives last season; and others’ are thriving. Here’s to beekeepers everywhere and their pursuit. Keep on keeping on!

  • Doing an alcohol wash on dead bees is a ‘given’. Thought that was common knowledge, but I guess it was not. Mites are everywhere. Just can’t get away from them. We are ‘mitekeepers’ not ‘beekeepers’.

  • I would NEVER winter a hive with a queen excluder or without a generous top entrance. That said, could be insecticide in the honey. If weather is cold, bees cannot always get to their reserves, a problem here in NH, and I’ve had really strong hives starve due to using up reserves too fast. One trick I like- place an empty (no frames ) body on top of the cluster, place a 5 pound bag of sugar within it, slit open and saturate with water- short of making it a syrup. should be grainy and NOT flow. Bees will appreciate it immensely.

  • First, thank you so much for posting this. I love these discussions and find them very informative. And a couple of questions, please.

    RE: Deb in Ohio’s comment. Is anyone aware of research done that shows transmission of varroa-related virus passing from one hive to another via “contaminated” frames from deadouts? I’d like to read more on the topic.

    Second, re: Joe’s recommendation on doing alcohol washes on dead bees. Sounds like a genius diagnostic took, but why the alcohol? Wouldn’t water wash the mites off, too?

    Thanks very much.


    • Anna,

      I will need to do some digging because I lost track of the places where I read about these viruses, but the gist was that like many human virus, they can’t survive outside of a live host more than a short time, usually on the order of 15 minutes to an hour. So just letting frames stand unattended by bees overnight should be enough to “disinfect” them of viruses. I will try to find the papers.

      I agree about the wash. The alcohol is used to kill the bees and the mites, but if they are already dead, why not use water?

  • Rusty
    I see no indication of eggs in any of the pictures. I do see many reflections of dead larvae, however, which resemble eggs, and traces of sugar which I often see in my hives at this time of the year. I have had similar die-outs with new late queens that were likely robbed to near extinction, because of a couple small holes in the back of the hive and placement near a very active hive.
    Roca, NE

  • I would highly suspect varroa. The question I didn’t see answered was when his counts were low. Mine were very low going into August but jumped to over 500(in mite resistant bees) by the end of September and, because of the temperature, I used OAV to treat them 12 times from end of August to mid-November to get their counts down. I think the key is to treat, count and then continue to treat until the drop is less than 5. OAV did not seem to cause any ill effects even with 12 treatments and so far, they are all healthy and active. Why a queen excluder on during the winter? Isn’t there a danger the colony will move up and leave the queen?

    • Denise,

      No, the colony will not leave the queen or the brood. Retriever bees merely go and get the food and then bring it back to feed the rest.

  • Everyone should read this study. Lots of pictures. You can see at the end how the bees are poking holes in infected cells because they know the contents are infected. I am not a scientist, nor am I a bee specialist, but I DO NOT TAKE CHANCES WITH MY BEES. If you have no clue as to why the bees died, why would you take the chance of spreading anything to another hive? Just to save the honey? the frames? Doesn’t make sense to me, but every beekeeper has to decide for themselves how they want to treat their bees. To me, if food is infected and food is in the hive that died, then the bees have to come in contact with it to remove it from the hive. I hope people do study this more as it seems bees need the help. Why wash your hands after touching a door knob if the virus dies in fifteen minutes? Why not eat food prepared by someone who is sick if the virus dies when ‘off’ the host? I don’t think researchers really ‘know for sure’ about these things, that is why more research is needed and caution on the part of the beekeeper. As people with a lot of hives know, if one hive gets infected, then a lot of them will as well. If I am incorrect, I am sure Rusty will help me understand it all.

    Honey bee viruses are not limited to honey bees. Honey bee viruses have been found in other non-Apis bee species, other colony inhabitants like small hive beetle, and in pollen and nectar (Andersen 1991; Bailey and Gibbs 1964; Genersch et al. 2006; Singh et al 2010). For more on honey bee pathogens found in native bees see here. Transfer of honey bee viruses from infected colonies to non-infected individuals or colonies can occur during foraging on common flowers or through robbing of weak or collapsed colonies (Singh et al 2010).

    Deformed Wing Virus (DWV)

    Deformed wing virus is common, widely distributed, and closely associated with Varroa mites. Both the virus titers and prevalence of the virus in colonies are directly linked to Varroa infestations (Bowens-Walker et al. 1999). In heavily Varroa infested colonies, nearly 100 percent of adult workers may be infected with DWV and have high virus titers even without showing symptoms (de Miranda et al. 2012). DWV is strongly associated with winter colony mortality (Highfield et al 2009; Genersch et al 2010). Control of DWV is usually achieved by treatment against Varroa, After treatment a gradual decrease in virus titers occurs as infected bees are replaced by healthy ones (Martin et al 2010). DWV can be found in all castes and life stages of honey bees and will persist in adults without obvious symptoms. DWV is also transmitted through food, feces, from queen to egg, and from drone to queen (de Miranda et al. 2012).

  • Some info on disease transmission. Everyone should go to this website and read it. It explains viruses and has tons of pictures. Don’t take chances with your bees. Bee cautionary.

    Honey bee viruses are not limited to honey bees. Honey bee viruses have been found in other non-Apis bee species, other colony inhabitants like small hive beetle, and in pollen and nectar (Andersen 1991; Bailey and Gibbs 1964; Genersch et al. 2006; Singh et al 2010). For more on honey bee pathogens found in native bees see here. Transfer of honey bee viruses from infected colonies to non-infected individuals or colonies can occur during foraging on common flowers or through robbing of weak or collapsed colonies (Singh et al 2010).

    Identification of a virus is difficult due to the small size of particles. Expensive and often uncommon laboratory equipment is required for accurate diagnosis. However, symptoms of some viral diseases are more visible, especially with overt infection. A lack of symptoms does not rule out the presence of a virus. Viruses can remain in a latent form within the host, acting as a reservoir of infection, complicating diagnosis and control, and only becoming an outbreak when conditions are right.

    Deformed wing virus is common, widely distributed, and closely associated with Varroa mites. Both the virus titers and prevalence of the virus in colonies are directly linked to Varroa infestations (Bowens-Walker et al. 1999). In heavily Varroa infested colonies, nearly 100 percent of adult workers may be infected with DWV and have high virus titers even without showing symptoms (de Miranda et al. 2012). DWV is strongly associated with winter colony mortality (Highfield et al 2009; Genersch et al 2010). Control of DWV is usually achieved by treatment against Varroa, After treatment a gradual decrease in virus titers occurs as infected bees are replaced by healthy ones (Martin et al 2010). DWV can be found in all castes and life stages of honey bees and will persist in adults without obvious symptoms. DWV is also transmitted through food, feces, from queen to egg, and from drone to queen (de Miranda et al. 2012).

  • Were there frames with pollen? Besides the pathogen possibility, I would also note that pollen can contain stored pesticides. The summer die-off is also a clue of a pesticide hit, then possibly toxic pollen could be covered with fresh pollen and not uncovered until the bees are highly vulnerable in winter.

    A test could provide another clue – put a frame of pollen from the deadout and place next to the brood into a healthy nuc or hive with a good queen. If the queen looks to be failing after a 3-4 days, I’d suspect the brood is being poisoned by contaminated pollen, and then being removed by the workers.

  • Thank you for the information. It underscores for me the need to keep mite levels low to prevent an epidemic. We went from no treatment (because someone, somewhere insists they don’t treat and their bees are the better for it), to some organic acid treatments, to a combination of amitraz and organics. We test throughout the warmer months, and currently are averaging four treatments a year, two Apivar, and two organic acids, always mindful to alternate them.

  • Having lots or ‘bee poop’ all around hive on snow. It is black spots and seems more each time and lots of dead bees on the ground. Been feeding well all winter. Hive been active and some dead bees in hive also. Any thoughts as to cause?

    • Ann,

      Bee poop in the snow comes from the bees taking cleansing flights in order to relieve themselves, the difference from normal is the snow, which allows you to see it. Same with the dead bees. Bees die and are carted out all the time, but snow allows us to see them.

  • It’s probably Nosema C. I had all the same signs. It’s a silent killer as you say – dysentery is not a requirement for Nosema C. I took the dead bees to a microscope and there were more spores in one view than I had ever seen. I’d be curious to see if he could get the bees to a microscope to look for spores. People do not check enough for Nosema C.

  • There were suggestions of doing an alcohol wash on the dead bees. Do the varroa stay on the bees once they’re dead? I tried examining dead bees under a microscope and couldn’t see any varroa. I assumed this meant they’d just fallen off, not that there weren’t any.

    Any thoughts?

    • Andrew,

      That’s the reason for the alcohol wash. The mites are really hard to see. If you are checking under a microscope, you need to pry the tergites apart and look underneath them, especially in the area of T1 and T2. I don’t know how long the mites stay on dead bees, but they are not skilled at getting around unless they have a live bee to carry them.

  • Not sure if this is the place for this but…

    Last week was sunny and reached the upper 50s and I did a postmortem on West, who had been Not Dead Yet when I postmortemed North and South.  This was the most interesting postmortem I have done, which is not a good thing.  This was the first deadout I’ve seen where moisture was an issue.  West had a layer of packed moldy wet bees on the bottom board (deeper than the entrance) and between frames.  I think her robbing screen did not work out for her, possibly because she gets more shade than the other hives.
    She did have an upper entrance, but there was spider webbing with a dozen or so webbed bees at the upper entrance between the inner cover and the insulating boards above.  I had cleaned out the dead bees blocking the main entrance shortly before West succumbed, but that was obviously too little, too late.

    I did find the queen in a tiny, tiny cluster.  Plenty of honey less than an inch away, so the small cluster was the problem, not the lack of stores.
    I swished a handful of dead bees in a bucket of water and counted 11 mites as I poured out the water.  I assume there were many more, since I didn’t even move to sunlight and I have very bad eyes.  So despite the moisture and despite the presumptive spider and despite the tiny cluster ultimately starving/freezing, none of which helped, this colony most likely died of varroa.

    (I did not have nearly as much “help” from live bees as I did the first time I attempted postmortems on South and North, which I hope means Observation and East were finding some nectar out there somewhere.  I could see that they were bringing in pollen, but my area could have plenty of freezing nights still to come.)

    I realize there isn’t a question in here, so I suppose I am looking for agreement/disagreement, or maybe just commiseration.

  • I have learned on this site that moldy frames from a lost queen in the fall (resulting in a lost hive this month), does not mean throw the frames away. I am going to use a few of them in the new nuc I am to receive next month, but I don’t know how many I should bombard them with. Both deeps have mold but the lower one has the most. I have many. How many should I use in the new hive and should I put some in my other, robust hive. There is no indication of AFB. This hive has been in my living room for several days now. There is still a lot of honey (covered with mold) in the hive I lost. I don’t want to discourage honey making in the hives by giving them too much, or diverting their work to cleaning up too many of these. However, I’d love to redeem all the frame if possible. Is it?

    • Hi Susan,

      Mold is a fact of life for bees and they know how to deal with it. Last spring, I had a completely moldy hive that sat outside all winter while I procrastinated about cleaning it up. When I least expected it, a swarm moved in and started cleaning house. I had beautifully prepared bait hives within yards of it, which they completely ignored in favor of the moldy mess. Now, one year later, that colony has overwintered and is thriving.

      The message here is don’t worry overly much about the mold. In spite of this story, I don’t like to overwhelm a colony with a lot of moldy frames so, if I have control of the situation, I give them a few frames to clean up at a time, and later add some more. There is no scientific reasoning here, it’s more emotional. If I had to live there, I’d rather be faced with a few frames than a whole bunch.

      Honey bees always clean and polish they wax combs before they re-use them in any case, so they will clean up the mold as they get to it. Interestingly, some researchers think mold keeps away some of the brood diseases, like foulbrood, possibly because the mold inhibits spore germination. Again, I don’t know for sure, but it wouldn’t surprise me.

    • Susan,

      Forgot to mention that having a supply of honey in no way discourages bees from making more. Where forage is good, honey bees will fill 10 or 12 supers, one atop the other. They never say “enough.”

  • I think it is a mistake that we all completely ignore tracheal mites when considering the causes of winter die-offs.

    It’s not always correct to blame varroa. Big productive hives in summer often succumb to varroa mites in fall and early winter. But IF, as seemed to be indicated, this hive was strong in fall, and with low mite counts by a reliable method… and there are no disease symptoms… and the bees dwindled in mid-winter, it would be logical to suspect tracheal mites. Tracheal mite infestations can explode in the winter even if almost non-existent in the warm season.

    Some of the varroa treatments also target tracheal mites. However, since these hives were not treated with any of those, I think tracheal mites should be entered into the equation.

    It is nice that varroa washes can be done postmortem, as well as nosema investigations, and by all means, those should be done. If those are negative, again, tracheal mites should be suspect. (By the way, yes, alcohol works much better than water when doing mite washes even on dead bees and mites because of the gravity issue. In water, you will have bees floating and sticking to sides, etc. They will flush out of the wash / settle through a screen much better in alcohol.)

    Once again, I think our modern habit of completely ignoring and forgetting about tracheal mites is causing some misdiagnosis of some deaths. Tracheal mites are still around, and it is not reasonable to imagine and assume all bees are completely immune to them.

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