Screened Bottom Board debris - can anyone identify

Hi there - can anyone please tell me what this is ? I’m in Katoomba NSW Australia. I put a new SBB under hive only7 days ago and this is what was there today when i checked. I checked inside the hive about 3 weeks ago and all seemed ok although there were a few cells which looked like dead bees (chalk brood? top left area of close up below) I will check the hive again as soon as it stops raining. I think there may be pests or disease in there?
Thank you so much for your wonderful always helpful advice.

That is chalkbrood (caused by a fungus). Those black or black and white things are dead bee larvae which have been killed by the fungus and removed by the bees (they are called chalkbrood mummies). They fall onto the corflute. Some get caught in the screen wire, particularly if the corflute is in the bottom slot.

Yes I agree with @Dan2

Thanks @Dan2 .
With there being so many- do you think thats a sign they are dealing with it and eventually the hive will heal itself - or it’s an increasing problem? Katie

Hi Katie,

Well, as a matter of fact, I am a chalkbrood expert as it happens…that is an expert at getting it in my hives! I can’t get rid of it to be honest.

It started when a hive got weakened, but it spread around all my hives quick smart. It is very common. I have two hives that have a lot of it, and one hive that seemed to get it but is now clear of it. Probably the worst hive I have with it is bursting at the seams with bees, and has been for a while. It re-queened itself but nothing has changed. I have tried a few different things which initially appeared to work, but I don’t try anything now apart from keeping the hives compact. Perhaps a new good queen from someone else might fix mine, but I can’t buy queens.

Just as a matter of interest, is there a good supply of nectar where you are, or have you been in a dearth?

I would say average. Good odour of honey coming from the hives for past few weeks, but I have haven’t harvested any hive from my FlowHive (Hive #1) yet this season. pic below was 3 weeks ago. That hive has 1 x brood, 1 x ideal, 1 x flow. Have harvested last season though and there is plenty of honey in the ideal. Cant see any chalk brood evidence in #1.

This Chalk brood from above is hive #2 and nuc was only installed in Spring.

Ok…so the chalkbrood hive is comprised of a langstroth 8 frame brood box only at this stage?

I am new too, and found chalkbrood yesterday on the landing strip of my very young hive. When I called my bee expert friends they suggested putting a very ripe banana, cut in half lengthways, into the top of the hive. Apparently the chemicals it produces while rotting encourages the bees to do a big cleanup. Worth a shot.
(East Gippsland, Victoria.)

I wouldn’t accept that amount of chalk brood
It’s a fungus and is exacerbated by cold and damp.
Many bees are resistant.
If your hive is in neither a cold or a damp place I would change their genetics. I’m not telling you what to do but I would change

There is no real treatment for chalkbrood (which is what you have of course). You can requeen. The fundamental cause is chilled brood. Humidity may be a contributing cause. Lack of hygienic behavior may also contribute.

1 Like

I had a hive with a similar amount of chalkbrood. It came also from a Nuc (from a commercial beekeeper). After 6 months it cleared up all by itself. Maybe what happened was that it came from a cold or a damp place- then recovered once it was at y location? Or maybe the bees requeened themselves with some local genes infused? Whatever the case I havn’t seen a single mummy in months now.

1 Like

Hi Michael- how would you requeen a chalkbrood hive?

Hi Dee-do you have any advice please as to how to do this?

Does anyone think that chalkbrood has anything to do with poor conditions ie. poor nectar and pollen supplies?

Hi Dan, Michael probably means to kill the old queen, then introduce a new one, I’m sure that Dee is referring to the same thing.

As well as that, you can change the brood box & bottom board. Then sterilize the original one. I have done that as well as a complete change of brood frames. The badly affected brood frames can be cut out & then refitted with fresh foundation. The not so badly affected frames can be placed above the QX of another colony.

This is one reason why I like a solid floor. Easier for the bees to keep clean.

How much harder would it be for us to keep a tiled floor clean if we didn’t grout the gaps than it would be if we grouted the gaps? I’m thinking of smaller tiles than they use today. Say 8 by 4’s for example.

-thanks Jeff. I agree about the solid floor and chalkbrood.

I wondered if they meant perhaps getting the bees to raise emergency queens? The problem there might be the falling numbers in the hive for a while and the risk of a queenless hive, but perhaps that is not right. There are no queen bees for sale in Tasmania - and probably no one on the mainland either who would send one or two queens to a backyard beekeeper here either. That has been my experience in the past on several occasions.

I’m pretty sure that they are talking about bringing in new queens. What I would do is do the complete brood change. Maybe you could take a small nuc away with the old queen as backup. Then let the remaining colony make emergency queens with brood from a clean hive.

It certainly pays to have at least a few hives.

I did the whole thing that I’m suggesting about a month ago, except that I killed the queen. I split the colony in two & let them make emergency queens using brood from other hives. I guess you could do that if you’re worried about the emergency queen failing.

In my case, one of the emergency queens failed, they are now making a new one with fresh brood. I’m still waiting to see if the other queen is laying fertile eggs. However it looks promising. The bees are cleaning out large areas for her to lay in.

1 Like

Yes you need a new and completely unrelated queen
If you raise a queen from the same hive she will have similar characteristics, though her daughters will have them diluted.
People go on about the causes of chalk brood. Yes, it’s a fungus but Michael is right. The main cause is chilled brood so that means not enough bees or prolonged inspections.

1 Like

Thanks Dee. As I’m stuck with my own bees and queens, I wonder if that means it will remain a constant problem or even get worse over the years as new queens come on?

Have you a hive that doesn’t have chalk brood? Raise a queen from them. Or get a mailed queen, make a nuc, introduce her and when she has laid a frame of brood remove your chalky queen and unite the two colonies.

1 Like

There are many ways you can requeen. One is to catch the old queen and keep her somewhere temporarily. Either caged with attendants and candy, or in a small nuc. Cage a queen from a colony that doesn’t have chakbrood in a candy cage and introduce her to the now queenless chalkbrood colony. Let the donor colony raise a new queen. Once every one is queenright again, drop the calkbrood queen in some alcohol for future use as swarm lure.


Thanks very much for the advice.

I do have a hive that seems to be on top of the chalkbrood, but as my three hives all have queens that came from the same initial queen, my worry is that they are all so closely related that they would produce offspring with a similar genetic weakness. I assume I am wrong about that because of the advice you have both given, but don’t understand I guess.