Chalkbrood - What is it and how can I manage it?

Chalkbrood is a fungal disease that attacks the brood of a colony and can cause harmful damage if not managed by the beekeeper. Over time chalkbrood can kill a significant amount of brood (mummifying sealed larvae), weakening the colony making them much more susceptible to other disease and pests.

I’d like to ask the forum how others manage this disease in their apiary or hive. For example, what are some key steps to cover as a means of prevention and are there any quick solutions for management?

I think its best to view chalkbrood as a symptom as much as a disease in itself.
All hives have chalkbrood spores. Disease is evident when something else is wrong in the hive either stress (weaher, feed, queen issues) or some other underlying condition. Identify this, fix it and the chalkbrood will go away.


Such a great answer @JimM!

my own experience with chalkbrood mirrors what Jim said. It can be viewed as similar to wax moth or beetles as an issue. It seems it is always there dormant- waiting for the right conditions to take hold. I have observed here in Adelaide that it is a seasonal thing. Last year in spring and summer we had a bit of it in many hives. This year hardly any at all. The best defense against it is to build up strong hives.

I have been told that it is related to chilled brood, so the best way to stop it is to make sure that hives are kept full of bees. That means not putting supers on until the box below is packed with bees, not transferring nucs into bigger hives until they are strong and crowded, taking care with checkerboarding frames and only doing it during good weather and with very strong populations. It might mean moving a hive out of a shady and/or damp position.

A month ago I had a strong hive that had no chalk brood at all. I went into the brood box and found the outer two frames were all honey and pollen. I decided to remove them and also one frame of eggs to donate to a queenless nuc. I checerboarded the new foundation frames into the brood box. Two weeks later I observed some chalkbrood mummies being thrown out of the front of the hive. It seems I went too far breaking up the brood cluster and the brood got chilled allowing the chalk brood to get a hold. In spring I could have down the same without any issue- but things had slowed down and we have had a very cool summer. As that hive is still very strong I expect it will soon recover.

At times a weak brood box with chalk brood would be better off condensed down into a nucleus until it builds back up.

Some people place a banana cut in half length-ways on the top of the brood frames to stimulate cleansing behavior. Others believe it is a gas that the banana gives off that inhibits the chalk brood spores. I have tried it but can’t really say that it helped- it may have I am not sure.

others say that if a hive doesn’t recover over time re-queening may help- as the original queen may have lacked sufficient hygienic behavior.

The good news is that in the end chalk brood generally just disperses if the colony is kept strong.

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I completely agree with @JimM’s response above. However, I have some things to add that even seasoned beekeepers don’t always remember. I am sure that @JeffH will be able to add even more comments. In no particular order:

  1. The most common cause of chalkbrood is chilled brood. With a new beekeeper, this may be from them inspecting in poor weather (cold, overcast, windy, wet) or taking too long over the inspection. My suggestion to prevent this is only inspect when the temperature is above about 62°F (17°C) and preferably higher. The number I give is a lot lower than most Australians, but in the UK, if we used the 22°C often suggested, you might only be able to inspect on about 4 weekends per year! It works fine in lower temperatures if it is not windy, wet and you are fairly quick
  2. Wet hives with condensation will chill the hive. Make sure it is dry and insulated in winter, otherwise coming into spring, you may face chalkbrood
  3. Keep your hives strong. If they begin to weaken, condense them down into a smaller space with dummy/follower boards or even moving them to a nucleus box. Bees prefer to be crowded than sparse
  4. If you have more than 10% chalkbrood on a frame, consider removing the frame, or cutting out the affected area if all mummies are close together. Mummies are very hard for workers to remove, and spread infection as they are discarded by the hive
  5. If your queen is older than 2 years, consider replacing her. Queens can be the source of a spreading infection in the absence of other factors

As far as quick solutions are concerned, I don’t think anything sensible is quick, but I am willing to listen to others. I would pursue all of the items above, and if the hive is weak, perhaps try to obtain a frame of capped brood and nurse bees from another stronger hive to boost the worker population.

Just my 2 cents… :blush:

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I agree with what you said Dawn.

On 2 occasions, the only thing that fixed the problem was a new queen. The previous queens were also new, however their progeny didn’t exhibit the behavior required to clean the chalk brood mummies out.

Something to add is doing brood inspections during cool windy weather. Wind can blow directly onto the larvae & chill it. With no wind the honeycomb itself acts as a kind of insulator over a short period of time.

PS. Sorry @Dawn_SD , you said “windy”

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A newbie beek sent me a photo of what appears to be chalkbrood. He has cleaned this up but more have appeared since 5 days ago.

This is a continuation of what happened after we suspected the queen was accidently killed on a previous inspection:

I suspect the colony hasn’t built back up enough and may need to be reduced down in size. Should we take the super off? Perth has experienced a wet/cold spring. But it’s getting warm now as we move into summer with plenty of forage around.

Might throw in a ripe banana for good measure…

Hi Fred, I would take the super off, especially if the bees are not using it. Give the bananas a go, for sure. You’ll need to do a brood inspection, just to see how badly affected the brood frames are, because some of them might need removing. Reduce the entrance to no more than 15 sq.cms. as well as block any screen floor, if that applies.

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Hi @JeffH - I wonder what your main reason for removing an affected frame in the brood is, and what do you consider affected? Is it to remove the spores from the chalkbrood from the brood box? Have you tried and tested this method?

I’d recommend working on ventilation rather than blocking up the screen floor, such as by propping up the lid for a few hours in the afternoon of a warm day. Whilst also making sure the hive is in a sunny spot with enough direct sun (this is the most important step I believe).

Removing any unused boxes is also a great tip.

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Hi Bianca, it’s hard to put a percentage of how badly affected a frame is before I’d remove it. Somehow you just know when you see, say half of the brood on a frame is chalk brood, you just want to remove it because it saves the bees having to remove every mummy, which only keeps them in contact with the spores for longer.

I believe that wet damp weather promotes chalk brood, so therefore I suggest reducing the entrance size to the size that the likes of Tom Seeley recommends & leave it for the bees to regulate their internal environment via the entrance. Allowing more ventilation only lets more damp air into the hive which works against the bees in their effort to maintain a suitable internal environment.

The same thing goes for allowing more ventilation during a hot day, it only allows more hot air into the hive.

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We inspected yesterday afternoon - was a bit windy so we worked quickly. We were greeted with entrance full of mummies, so our plan of attack was to check for laying queen, remove the super, shake all bees into brood box, removed undrawn drawns from broodbox, add banana and reduce hive entrance.

It was very obvious after opening the box that the populous was very low in relation to the space. The queen was laying, but the brood must be getting chilled in the process due to the sparseness. Noted some dead bees, but left them there for the colony to deal with. We took frames of nectar/pollen and honey from the top box and flanked the brood box after removing a few frames of undrawn frames (which were plastic).

We expect a few more mummies to be thrown out and will inspect in 2-3 weeks time to see how the colony is going. Will be interesting to see how much of that banana is left also.

Hi @Bianca,

Of cause just removing a few frames will not remove spores from the hive. In cases of serious infestation, a more holistic approach is needed. Frames with infected brood should be removed and the wax melted. Melted wax must not go back to the beekeeping industry unless there are facilities capable of processing infected wax in the country. Honey must be used only for human consumption. The colony must be moved to the clean hive with new frames. All brood older than 3 days should be quarantined with accompanying bees in a separate box. Old equipment should be disinfected one way or another. If there is a possibility to irradiate all infected materials and equipment, wax melting is not really needed and honey can be fed to bees.
In the case of mild but persistent ascosphaerosis in the apiary, the same approach can be applied at the beginning of each season to clean up the apiary gradually.

To be honest, the whole idea of diagnosis and treatment over the internet makes me cringe. Even in the case of chalkbrood. When dealing with ascosphaerosis without medications, it is impossible to come up with a single method that will suit any occasion. One needs to know local conditions, what strain of the ascosphaera is present, how much hive is affected, what other diseases are present, what treatment has been applied, etc. Then a decision could be made based on knowledge of bees and the fungus economy. And still, it may or may not work because all we can do is to create a condition less favourable for the fungus and hopefully more supporting for bees.

Let me illustrate the point.
Ascosphaera spores remain viable at 27°C for 4 years.
The optimum temperatures when ascosphaera produces spores: Ascosphaera major 20°C, Ascosphaera apis 30°C. We can see that high temperature is less favourable to the A. major. but A. apis will be less affected.
Is your hive located in the Australian desert, tropics or in the middle of the Irish bog?
Varroa present? This means bees are weakened and more open to ascosphaerosis.
Oxalic acid applied? This often creates more favourable conditions ascosphaerosis.
Differential diagnosis. Are we sure that our distant fellow beek is capable to exclude aspergillosis? Because if it is aspergillosis, forget bees, the beek may need treatment now.
The list goes on.

But even if we will take into account all possible variations and say what is to be done in these particular circumstances, there is a good chance of a second opinion. And banana always wins :rofl:


Hi Fred, going by what you said about the population being low & thus the brood getting chilled, I think a good strategy would be to introduce a heap of nurse bees that will assist in keeping the brood warm, as well as helping the colony to get on top of the disease.