Colony Post-Mortem

Colony Post-Mortem – First 2015 Winter Loss

Post-mortem: An examination of a corpse in order to determine cause of death.

I need your help with the determination. There are comments and photos below and a video at the end.

Beekeeper Inspecting Dead BeesBeekeeper Inspecting Dead Bees
Me Inspecting Dead Bees

Was It A Weak Colony Going Into Winter?

No. This hive had 11 frames of bees in September and there were live bees in the hive over Christmas. That said, there only appeared to be about 500 dead bees in the hive (see photo above). Had the others absconded or died over the winter and been removed from hive by the live bees?

Was It Starvation?

I don’t think so. The frames were heavy with stores and I don’t think the bees could have been isolated.  A few bees had died head first in the comb – but very few.

14x12 Frame Of Stores
14×12 Frame Of Stores
Sugar Stored In Comb
Sugar Stored In Comb
Pollen In Frame. Is that white pollen on the left or sugar stores?
Pollen In Frame. Is that white pollen on the left or sugar stores?

Was It Disease?

I don’t think so. There is mould in the frames (see photo below) but no chalk dummies. There was no foul smell.

Mouldy Frame - But Not Chalk Dummies
Mouldy Frame – But Not Chalk Dummies
Frame With Pollen (& Sugar Stores?) On Left; Mouldy In Centre
Frame With Pollen (& Sugar Stores?) On Left; Mouldy In Centre

Was It Varroa?

Maybe. Despite a (low/middle) varroa count of 130 in mid-July (I counted 30 mites over 9 days in July and put this into the NBU calculator which estimated I had 130 mites), followed by Apiguard in August and Oxalic acid in December, there did appear to be lots of varroa on the frames and on the bees. See photo below – I count over 20 mites in a small area. Did this contribute to some sort of colony collapse?

Varroa On Frame
Varroa Mites On Frame

Did the Queen Stop Laying?

Maybe though I saw capped brood and dead bees about to emerge out of cells (see photo below). Cappings are a bit ragged which I think might mean varroa.

Dead bees emerging from cells
Dead bees emerging from cells
Dead bees emerging from cells (2)
Dead bees emerging from cells (2)

Did They Get Too Cold?

Maybe. The location is quite exposed. I have not put insulation under the roof of this hive. The entrance points into a prevailing wind (but it has narrow entrance plus mouseguard).

Was It The Move?

I moved them 100m over Christmas. Perhaps some of the bees returned to their old hive location?


A lot of maybes and no certainties. Frustrating. Such is the life of a beekeeper.

On a positive note, I feel like I have done as much as I could for this colony. It seemed to be strong (and aggressive).  Hence, I’m not as upset as when I feel like it has been my fault. Overall, I’m sorry for the bees that have gone through this experience and disappointed as it means less bees and honey this summer.

Video Of The Inspection

Hmmmm. Not sure if I should expose myself as such a novice? I struggle to just get the frames out. And I seem to be wearing a bee suit when there are no bees. Apologies for the out of focus shots of the comb.

And if you want more information, I have my notes for the last 12 months on this hive: Hive Five Record Card.

Over To You

  1. Grateful for your thoughts on why this colony died?
  2. What should I do with the frames that are mouldy in the hive? Leave them and let next bees clean it up? Or cut out the mould?
  3. On some of the photos above, is it white pollen or sugar stores?

Read More


Based on comments to-date and my experience of this colony, I am minded to think that the main issue was the high varroa count and that insulation and the move whilst not helpful were not the prime causes.

Lessons learnt: I’ll apply Apiguard correctly next time. I didn’t seal the hives as per the instructions to get the best efficacy.

Next steps:

  1. Freeze and reuse the frames (getting rid of the dark comb frames)
  2. Apply MAQS strips to the other hives when it gets to 10C and 6 frames of bees (I’m worried about the other colonies now)
  3. Insulate the roofs and get solid crown boards to reduce drafts in winter
  4. Perhaps insulate the walls further for the hives that are more exposed

Author: Roger

regaining my sanity through beekeeping

26 thoughts on “Colony Post-Mortem”

  1. If there’s a reasonable amount of Varroa at this stage of the season I’d bet the mites (and more correctly their viral payload) were responsible. With no brood rearing since late last year there should be very little Varroa in the hive, other than phoretic mites that remain after incomplete Apiguard or OA treatment. If you look at graphs of Varroa levels in a colony during the season (try Randy Oliver’s Scientific Beekeeping site for example … like the one on this page: Fighting Varroa) you’ll see they should be minimal at this stage. High mite levels amplify the amount of deformed wing virus (in particular) which is known to shorten the life of bees. If the colony went into the winter weak, with high Varroa levels and with a high virus load, it wouldn’t surprise me if the bees have simply dwindled away. There don’t appear to be many bees on the floor- which makes me think the colony wasn’t hugely strong – and there appears to be ample stores. Not sure about the white stuff … probably crystallised honey at a guess.

    However, I’d not trust any of the frames and would steam the lot out to sterilise everything before scrubbing/flaming the hive clean

    1. Thanks David. I did a complete 4 week treatment of Apiguard in August and full trickle of oxalic acid at Christmas – but there were a lot of mites as you can see in photos above. Maybe the warm weather in September and beyond extended the brood rearing season and hence mite breeding season?

      If you were sure the hive was disease free – what would you do with the mouldy frames? Cut it out or let bees clean it up?

      1. A new colony of bees will clean up the mold. But, seal those frames in a plastic bag, then freeze for 24 hours to kill any waxmoth eggs and larvae. Keep the bag sealed in a cool mice-free place until you’re ready to put them on another hive.

    1. Most dead bees on the hive floor.
      There were maybe 50 dead bees on the frames. Some had their heads in the cells that had been feeding.
      There were also some new bees ready to emerge from cells.

  2. Hi Roger
    I’ve lost 2 this winter one from a virus no clean signs same as you .
    Another possible pestercide in garden mass of dead bees in front of hive classic sign .
    Hope this may help a little

  3. About 85% of the mites in your hive are still in the capped cells — they therefore cannot be counted.

    Mites will shorten the life of a honey bee by about a third. That early death begins when the bee is still in the pupa stage due to both parasitism and transmission of viruses. A honey bee thus weakened is unlikely to live through the Winter.

    In a mite-free colony (ah, the good ol’ days) about 20% of the bees die of old age before spring. The remaining 80% constitute a colony strong enough to keep itself warm through the Winter and meet Spring with a vengeance. But, a mite-infested colony will lose at least 70% of its population during the winter due to the above-mentioned shortened lifespan. The remaining 30% simply aren’t enough to keep the cluster warm enough to survive — even if they have plenty of food.

    The mite population MUST be controlled by mid-August (northern hemisphere) in order to have healthy winter bees. I recommend counting mites every 2 weeks beginning in the Spring. Treat when a sugar-roll test of 1/2 cup of bees reveals 6 mites.

    Low-effectiveness mite controls such as sugar dusting, green drone frames, etc. must be conducted very frequently — as soon as you reach that 6-mite threshold. The chemicals are harsher, no doubt, but they work (except in cases of resistant mites). Apiguard (thymol) is a good treatment, but the picture of Varroa you provide indicates to me that your mites were too out-of-control for such a soft treatment. Your oxalic acid treatment would probably have saved your bees if done in August.

    1. Thanks Blaine. It could have been a high mite count, shortening their lifespan and weakening the hive. I wish I had done more counts, but we had our second child in September and life has been busy. I also wish I had taped up and sealed the hive more thoroughly when I applied the Apiguard. I will consider using the MAQS strips on my other hives as soon as temperatures reach 10C.

  4. Oh no 🙁 So many bloggers I follow have been losing bees, it’s so sad when we work so hard to look after them. From reading your record card it sounds like you did everything right, after all you treated twice for varroa and fed in autumn. Perhaps extra insulation would have helped since you were using larger than average frames, but who can say – perhaps it wouldn’t have made any difference.

    One thought about the possible disease issue – nosema is very common, invisible and not always associated with dysentery. Infected bees tend to altruistically prevent spreading the infection by flying away and not returning to the hive. Nosema spores can remain over a year on combs unless treated with acetic acid (they aren’t destroyed by freezing). For that reason I would be tempted to destroy the frames or at least fit them with new foundation. It’s more expensive to destroy the frames but then buying new bees is even more expensive.

    I notice in your record card that the bees were very aggressive. Hopefully it might be some small comfort that you didn’t lose nice bees.

  5. It is gutting when all the effort comes to nothing. Sometimes it feels like the bees are just looking for new ways to die. Having had a similar mystery loss as yours I now feed sugar paste throughout the winter into spring at least then I know food is close at hand even when I know they should have “enough”and as soon as the weather warms up I will be using mite away strips which I have found way more effective and user friendly than apiguard. More expensive perhaps but if you only have a couple of hives it’s worth it rather than lose them. Last year it helped me salvage a massive mite load to end up harvesting some excess .The weather helped of course but I will be using this product again this season (having seen it first on the Bee programme Martha Carney made last spring)

      1. I feel I should say that some beekeepers I know have lost their queens after using MAQs and also our local inspector has warned that giving the same queen both oxalic acid and MAQs treatment may weaken queens. However, other people I know have had great results with MAQs and swear by it.

  6. What a pity. I suppose it’s a consolation that the colony was aggressive and you didn’t enjoy inspections, and it gives you a set of spare boxes for the coming season.

    There’s no sign of dysentery, plenty of stores, but few bees, which hints that the colony either swarmed at the wrong time, or for some reason dwindled to a size too small to survive. If the latter, the culprit could have been N. ceranae, but without microscopy you can’t tell.

    I’m tempted to guess they went queenless just after you last saw an area of brood, either that or they were trying to raise a new queen after a swarm and she didn’t mate well – but it’s a fairly wide of the mark guess because, although your notes say you last saw brood on 6 July, I think there were a few cells of dead brood in your video. I couldn’t tell if the cappings were chewed, which could hint at varroosis, or could also suggest those bees were ready to emerge but died before they left their cells.

    1. I wasn’t able to inspect them after July as they were so aggressive. I now suspect the aggression might have been due to distress caused by varroa mites.

      For info: I saw that about 2 bees were ready to emerge from their cells but had died before they made it … so there must have been a queen 24 days before the colony died.

      I’m also coming to conclusion that the death of colony might have been mite overload.

      1. You’re probably right, with little or no brood all the mites will have been on the bees. Any larvae would have had a very hard time of it, with varroa jostling for somewhere to lay.

        Were they all drone cells? It’s 24 days for drones, 21 days for workers. The laying pattern is quite random, but could easily be explained by all the other cells having developed. Did you manage to find the queen’s corpse amongst the dead? They can be quite hard to find

  7. Roger I sympathise, having had a similar experience myself on more than one occasion. You should also be congratulated for laying yourself open. Nothing to be ashamed of asking why and admitting something’s not gone right.
    I agree that the varroa theory seems most likely but would also like to pose a question or two: you treated twice for varroa. Why? Most bee keepers use either one treatment or another don’t they? Oxalic acid could be quite toxic to bees. Did you make your own fresh solution at the correct strength or did you buy fresh pre-prepared solution? How much did you apply? You’ve also moved your bees during the winter. Bees are very susceptible to vibration, particularly when clustered, so shouldn’t be moved apart from a very short distance (1m or less) is what I’ve always been taught. Finally on the frame and comb argument I would melt down the wax and clean up the frames before reusing. I don’t move used frames between hives unless really needed.
    Here’s to the new season, whatever it might bring.

    1. Thanks for your comment. In answer to questions:
      1. I treated twice as I understand that is quite common practice
      2. I used a ready made oxalic acid treatment and I applied the correct amount
      Getting excited about 2015 beekeeping.

  8. Really sorry to read this, Roger, it’s so sad. I’m in my first year with only one colony, so hardly an expert. My guess would be the move lost a number of bees and the exposed position chilled a cluster that could not keep warm. That would explain the small number of dead bees, the untouched food and so on. I’ve read so much conflicting blurb about preparing for Winter but elected, against some advice, to fashion a polystyrene cover for three sides and the roof -inside and out and have fed candipolline gold almost throughout the cold weeks. I used Beevital Hiveclean only against varroa, but treated 4 times, right into late November. So far so good. I tend to think you lost out through lack of warmth. Does the hive have vents at the top? I’ve read that these can cause a constant draught when used with open mesh floors and may do more harm than good? (Mine is vented as I read this was essential). I wish you all the best for 2015 whilst we both continue on our learning curves!

  9. Sorry for the belated comment but here it is anyway. I am really sorry you have lost your colony.

    I think the main problem is that you did not see the queen after July. Its quite possible that the queen was lost in the late summer or autumn and then the colony would just have dwindled away over the winter months. As the colony dwindled the remaining varroa would be concentrated on ever fewer bees, thereby magnifying the viral load.
    Also the hive was in an exposed location and not insulated. As the colony dwindled it would have been impossible for the cluster to maintain warmth. Cold weather in January probably just finished off the remaining bees.

    You have been vigilant on monitoring varroa through the season, and you treated with Apiguard in the autumn, and with oxalic acid in December. So you are not at fault there. You clearly had your reasons for not doing a full inspection in the autumn (i.e. aggressive bees), but I think it is important to be sure that you have a strong colony with a laying queen when doing your winter prep.

  10. Roger, so sorry to read of your lost colony. I really do appreciate your honesty and willingness to share all aspects of beekeeping. We have only had backyard bees for a year and being in Australia we have different issues to deal with, like a heat wave causing most of the combs with stores collapsing and melting through the bottom of our KTBH, and droughts affecting nectar flow. To balance it out we have less problems over winter. What you have shared has given us some insight about why our girls are being more aggressive lately, we assumed they should have “gotten over” their comb collapse by now! Perhaps not. Thank you again so much for everything you share. The learning curve remains permanently steep!

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