Nosema – Advice Required

Nosema – Advice Required

Synopsis: Colony has died. Evidence of dysentery (photos below). Possible Nosema. Not wanting to use acetic acid – should I destroy all the frames and boxes or use hot air gun? Details below. Grateful for advice.

A month ago this hive was looking quiet, with a few flying bees. There were also signs of dysentery (see photo below).

Hive One - Dysentery - Feb 2015

Hive One – Dysentery?? – Feb 2015

At the weekend I found there were no flying bees and opened the hive.

I found signs of dysentery.

Dysentery on frame

Dysentery on top and middle of frame

Dysentery on top frame

Dysentery on top frame


Dysentery on hive floor

Dysentery on hive floor (in middle of photo)

I found the dead queen (who was 5 years old).

Dead Queen

Dead Queen (with blue spot)

I found some dead bees ready to hatch out.

Unhatched bees

Unhatched bees


Due to the presence of dysentery it is possible that the colony died of Nosema.  Nosema is a parasitic microsporidian fungal pathogen that invades the gut of the bee. There they multiply rapidly and are then excreted by the bees. Spores are picked up and swallowed by other bees.

The only way to diagnose Nosema is by identifying the spores under a microscope. I don’t have a microscope (yet).

Dysentery is also often associated with Nosema. But the dysentery I found in the hive might be as per usual levels of winter excretion. Hence, I cannot be 100% sure the colony had Nosema.

If it was Nosema the spores can last 12 months and infect new colonies of bees placed in the hive.


The hive could have died due to one of the following reasons, or combinations thereof:

  1. Poor performing queen (as she was 5 years old)
  2. Cold (due to lack of insulation)
  3. Nosema (due to the signs of dysentery)

Reason 1 could have led to a weak colony and then to reasons 2 and 3.

Next Steps

Freezing frames does not destroy Nosema spores.

I have a hot air gun (heats up to 600C and does destroy the spores) but don’t want to use acetic acid as I only need to sort out one hive, don’t have the space for fumigation and don’t want to get involved with acetic acid at this stage in my beekeeping.

I am struggling to find good advice on the following options.

  1. Destroy all frames and boxes? This seems over the top and expensive.
  2. Destroy all the frames and use the hot air gun on the boxes? This will give near 100% piece of mind. But again looks over the top for a diagnosis of possible Nosema
  3. Destroy frames which have dysentery and use the hot air gun on the tops of other frames and boxes? This is my current plan but will not eradicate all the spores
  4. Hot air gun tops of all frames and boxes?

As ever – grateful for advice.

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Nosema – Advice Required — 8 Comments

  1. Roger
    Hot air gun or plumbers blow torch boxes scorch them.
    Frames I generally steam mine then when cleaned off old comb clean with a strong soda solution when dry new foundation
    Email if need more advice

  2. There are a number of reasons for dysentery the pictures are not conclusive for Nosema so I’d recommend cleaning the hive and frames as if they were contaminated but you don’t have to destroy the hive to get rid of it. First remove all comb from the frames and scrape all woodware. Next you are going to want to wash all woodware with either lye or oxalic acid as directed as a wood bleach. This includes every component associated with the hive. Then if possible wash and rinse everything with a pressure washer. Now let the hive completely dry out in preparation to be repainted and new foundation to be installed. I paint my boxes with an oil based enamel with a pint of copper boat bottom paint added mixed 1 pint copper paint to 1 gallon of enamel. I found the copper added to the paint makes a great fungicide that don’t effect the Bees and keeps ants away from the hive and makes a real tough paint. The oxalic acid is an extremely effective bleach. When your done it’s like having a new hive only cheaper.
    From the pictures and the age of the Queen I’d expect your Queen died of old age and the cold got the Bees when they stopped clustering because there wasn’t a Queen. Good luck

  3. Sorry to hear this 🙁 I have a couple of hives I’m worried may go the same way. Amazing that the queen lived five years.

    I agree with Colin, blow torch the hive boxes to scorch them. There’s no way I’d reuse the comb. It’s good practice to change the comb annually anyway and especially when a colony has possibly died from disease. Enough foundation sheets to fill a brood box will only cost you about a tenner, which is nothing compared to the cost of buying in new bees if you lose a colony.

  4. I got some good advice from the BBKA forum (see below). Might look into the acetic acid option.

    In my view, acetic acid is fine if you are sensible and it doesn’t go off, as far as I am aware, so it will keep. The quantity is 100ml – 150ml per box so you can keep it for use another time.

    The hive can be fumigated where it is – a bin liner will keep the fumes in for a week, then opened. As well as nosema spores, acetic acid will destroy chalkbrood (fungus), wax moth larvae and EFB (bacteria) so it’s useful stuff.

    I was surprised to see a 5 year old queen – not many get that far; I guess that she would have lost some of her vigor and had a longer quiescent period in winter than a young queen which might have contributed to their demise. Ther looked to be at least a couple of dead bees with their toungues out. This happens with parasitic mite syndrome (see the beebase varroa book). Were the bees treated for varroa in good time in late summer. And did you feed late which might have contributed to dysentry if it could not be capped in time for winter?

    The accepted method of dealing with a colony with nosema is a shook swarm or a bailey comb exchange onto clean comb. (It’s the clean comb bit that’s important). So if you sterilise your comb from the dead-out you can move the bees over to clean and then sterilise the comb the surviving bees are on now. (That’s 2 x 100 ml already!).

    The boxes can be scraped and shown a blow lamp. A scrub with a strong bleach solution and washing soda can also be used on scraped wooden parts.

    Acetic Acid (Ethanoic Acid as it might be called) can be obtained from the beekeeping suppliers – not all post it – or possibly from a local chemical supplier near you – I have just obtained some locally for much less that the beekeeping supplies firms.

  5. I also have a similar problem. A very healthy hive in autumn with a 2 year old queen. Very productive that summer and autumn. The hive was fed with pollen candy throughout the winter, which wasn’t very cold here in central Italy where I live. February there was some early activity but relatively few bees and then early March on an examination, very few bees and now none. There was no obvious sign of dysentery but the symptoms do seem like nosema.

    I wanted to ask if this is associated with humidity and damp. My hives are on stone slabs and then lifted up on wooden supports. I am concerned that the winter damp might have induced this fungal related nosema.

    This is the second time this has happened – seems to be spring dwindling. Any other ideas_

  6. Thats bad luck Roger,I would remove that hive or close it up so that no robbing occurs.The frames look quite new so I would dismantle the bottom bars, remove the combs and burn them and then scrub everything with Acetic Acid (Masemore Apiaries)and hot water, for a belt and braces job I would scorch all woodwork with a blow lamp then fit new foundation.
    To help with your expense I wont claim my £5 bet I made last month HA HA!!

  7. Thanks everyone for your help. Really appreciated and in future I might try out acetic acid. This time because (A) I assembled the combs incorrectly in the first place (i.e. glued the bottom bar as well as nailing it in, I only realised the error of my ways when I thought about it the following year) and (B) with 2 young kids and a boxes of Ikea flat packs to put together – I am under big time pressures. So I burned/destroyed all the frames and scorched the boxes, crown board, etc. with a hot air gun. Being cost conscious – I hope to be less wasteful in future. At least any possible Nosema will have been destroyed. Thanks again.

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