Chalk brood

[snimmo243]

One of my two colonies (bought as nucs last summer) had really bad chalk brood so I treat it with thymol last learning as I felt it was at a level that would hamper winter preparations. This seemed to help and they got through the winter fine and started building up well too, however at the last inspection the chalk brood was back with a vengeance. I think this queen is for the chop!
Interestingly/coincidently/completely unrelated (delete as appropriate) this colony has had a very low varroa count, consistently zero natural fall!

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[Jon]

Too much chalk brood is a pita. Changing the queen is the best option although it does get noticeably worse when the weather is poor and brood can get chilled.

[gavin]

Interestingly/coincidently/completely unrelated (delete as appropriate) this colony has had a very low varroa count, consistently zero natural fall!


I'd go for Interestingly. Noticed that before in non-treated survivors belonging to John McLean of W Stirlingshire. The chalky ones seemed more resistant. Was it just that that they lacked vigour, or was the chalkbrood somehow hitting infested cells? Or was it all imagination?

[Rosie]

I have heard it claimed that chalk brood is a result of a strain that keeps its nest slightly cooler than others. If true perhaps varroa like a warm nest too.

[Silvbee]

I've noticed the exact same thing with one of my colonies. Although I've also found the CB is worst in older, darker brood frames so I'll be carrying out a larger than normal frame change over this year.

[mbc]

I have heard it claimed that chalk brood is a result of a strain that keeps its nest slightly cooler than others. If true perhaps varroa like a warm nest too.

Cooper lists "FLUCTUATING BROODNEST TEMPERATURE" as one of his 23 behavioral characters of native bees in "The Honeybees of the British Isles", and quotes Italian colonies as maintaining a "remarkably constant 95 degees F"(35°C) compared to native strains under similar conditions ranging from 95 degrees F down to 65 degrees F (18°C) in the early morning after a clear-sky night. Unfortunately there are no references as to where, when or by whom this work was done and we are expected to take his word for it. He goes on to say "Breeders should learn to accept low to moderate attacks of chalk brood as indicative of their bees' possession of this habit" !!
I've just started reading this book and while finding it a good read I think I might take any recommendations with a pinch of salt.

[snimmo243]

I suppose the question is at what stage chalk brood becomes a problem and threat to colony growth? I am also in the process of working the old frames out of the hive

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[mbc]

Any chalk brood obviously peggs back colony growth, they invest time and energy into growing larvae only to have to spend more time and energy throwing them out and cleaning the cell.

[gavin]

I wonder if Cooper's fluctuating nest temperature (if true) is an inherent property or an effect of a smaller brood nest? Chalkbrood seems to decline as colonies strengthen, perhaps the opposite to some other problems (inc Varroa).

I was reading some papers there ... you can induce near 100% chalkbrood by chilling to 18C as late open brood then maintaining a lower temperature brood nest during pupation. Also, there is a paper from Tom Seeley's group that says that bee colonies have a 'fever' post infection with spores that appears to be a response to challenge, and is effective in reducing the problem. Just a small temperature shift, but possibly useful.

A propensity to chalkbrood might even help Amm in heather areas delay build-up to match the state of the flora. In a warm, dry season it may get away faster and take advantage of the better conditions. Assuming we have wet and dry years.

[mbc]

From "The Honeybees of the British Isles", "The character(fluctuating broodnest temp.) possibly assists in survival through adverse winter and spring conditions with reduced production of heat and hence a slower depletion of food reserves.......and not to worry too much over insignificant losses(from chalk brood) which they see."
Swings and roundabouts in the great balance of life and natural selection, or an apologist for an unwelcome trait?

[Jon]

while finding it a good read I think I might take any recommendations with a pinch of salt.

Very wise move MBC.
A lot of the AMM core beliefs such as AMM living longer than other races can only be found in 'Honeybees of the British Isles' and no other source.
His books are just his observations and his claims are not based on experimental work.
A good read but contains a lot of fiction.

[Rosie]

his claims are not based on experimental work.
A good read but contains a lot of fiction.

Are sure about that Jon? He was an entomologist after all and he claims to have marked young bees to test their longevity.

[brothermoo]

Cooper did mark young amm but there is no corresponding data from other races in that area that season so its not good science.

___________________________________
brothermoo.wordpress.com

[Jon]

He marked 100 bees and found some of them 3 months later. That is all he did. There were no controls with other races.

Proves absolutely nothing.

[Rosie]

It proves they can live for 3 months rather than the accepted 6 weeks. Didn't Wedmore say something similar about natives also?

[gavin]

Swings and roundabouts in the great balance of life and natural selection, or an apologist for an unwelcome trait?

Another cracking line from mbc! Probably both though.

Just about everything comes down to swings and roundabouts in the great balance of life and natural selection.

[Jon]

Rosie.
If you mark 100 bees from any race I bet you will find a few after 3 months. Cooper did not even carry out this basic control in what would be a GCSE level biology project.

[mbc]

Very wise MBC.



Another cracking line from mbc!

Ach! stop it guys my head is swelling!

To be fair to Cooper, he did earn his crust elsewhere, and all these tests would take a lot of time and effort to conduct in a verifiable scientific manner (not to say they werent, shame there isnt an easily accessible catalogue of this sort of work, isnt there a pile of similar sort of work by Mobus?) .

[Jon]

We had better stop criticising the Holy Scriptures of Bibba - the gospel according to Beowulf.

And on the hundredth day the black bee went forth and verily, they were all amazed and fell down before it!

This could bring a rain of frogs upon us all or worse still a fatwa.

[Rosie]

Rosie.
If you mark 100 bees from any race I bet you will find a few after 3 months. Cooper did not even carry out this basic control in what would be a GCSE level biology project.

That might be true Jon but has anyone bothered to do such tests other than Cooper? He tested his bees and has offered me one reason why I can see a hive of 6 supers, all full of bees, above a tiny nest in a singe national. As for his test not being a scientific comparison I can't remember him claiming that it was. In fact the only reason why we know that it was not a scientific study is because he was honest enough to explain what he did.

[prakel]

It's a long time since I had a copy of Cooper's book but if I remember right it was put together posthumously from his notes. No excuse for not noting gaps in the notes of course but to be fair to Cooper himself we'll never know how he would have presented the information he had or whether he might have wished to carry out more intense tests prior to publishing a book himself (possibly during retirement). The thing which sticks in my mind is that his peer, Donald Sims (while not subscribing to Cooper's idea of the 'best' bee), wrote about him in a positive way.

Interesting conversation none the less.

[drumgerry]

I do think the time is long overdue for someone to write the book that Cooper's book could have been. It seems nuts that there's no comprehensive modern treatise on AMM when there's so much interest in the subject. Someone needs to apply for funding for this - hint hint Jon, Rosie etc ;)

[prakel]

Not sure how good it is but I did once come across a reference to a modern German language book devoted to amm. If it lives up to it's hype it may just need translating.

edit:
http://www.nordbiene.de/das-buch-die-dunkle-biene.html

[The Drone Ranger]

Low mite counts on chalkbrood colonies might be the effect of mites being killed along with larva sort of brood culling
Thymol doesn't have much effect in reversing the problem in my experiments
Nor arranging for the mummies to fall through a queen excluder on the floor into a layer of hiveclean

Tried the heavy feeding with sugar syrup as recommended in Scottish Beekeeper
Bananas (Australian Idea) banana skins anyway (slipped up there)

The only effective method I have found is to shake all the bees into another box , floor etc. on clean frames new foundation
Then feed them some ordinary syrup no additive while they get started drawing the wax
The brood break probably helps as well

Often it stays gone so it might not always be the queen could be moving supers around etc

I just burn the affected combs now rather than treating them with acetic or any thing

[gavin]

Tried the heavy feeding with sugar syrup as recommended in Scottish Beekeeper


Ah, the 'Eureka! I've solved it!' article (with no controls or proper scientific approach?

[Rosie]

I find it's just a temporary spring phenomenon and clears itself as the colony develops. The best way of preventing it recurring next spring is to change to fresh comb. I can't remember ever having to resort to a change of queen although I am sure that some colonies are more susceptible than others. I came close to requeening once but they sorted the problem themselves in the nick of time. They must have heard me making plans to requeen.

Like DR I destroy all black or infected comb.

[Adam]

A couple of years ago I did an experiment and moved a chalk-brood queen to a clean colony and lo - that colony subsequently developed chalk brood instead of the first one! So that would indicate that the CB follows the queen, although clean comb would do no harm and might well help.

With regard to old books, Many of them were very subjective and un-scientific so I do have my concerns about them. Some were openly selling particular equipment of the day too. One I recall suggested a particular brand of petrol mixed up with god-knows-what as a cure for brood diseases. And there's the banging of pots and pans when a swarm issues and all that malarkey!

[prakel]

With regard to old books, Many of them were very subjective and un-scientific so I do have my concerns about them. Some were openly selling particular equipment of the day too. One I recall suggested a particular brand of petrol mixed up with god-knows-what as a cure for brood diseases. And there's the banging of pots and pans when a swarm issues and all that malarkey!

Petrol's still used to cure brood disease in some parts! It was also a constituent of the Frow mix wasn't it?

I reckon that a lot of the old books actually offer a lot of great value, I'm far from close minded when it comes to modern research but I wouldn't be without the old books either.

[mbc]

And there's the banging of pots and pans when a swarm issues and all that malarkey!

I've seen it work a treat, a swarm dropped from the sky and started clustering on a gorse bush within seconds, magic does happen!

[Jon]

A couple of years ago I did an experiment and moved a chalk-brood queen to a clean colony and lo - that colony subsequently developed chalk brood instead of the first one! So that would indicate that the CB follows the queen, although clean comb would do no harm and might well help.

I have seen the same Adam. I am sure there is a large genetic component in it.
I have moved queens back and forward between apideas and colonies for various reasons and a queen which has chalk brood in a full colony will also show chalk brood in the apidea and vice versa.

[lindsay s]

There's more than one chalk brood thread on this forum . Here's part of my post from last year which I still think is relevant.

The colony that was bad with chalk brood was of medium strength and on an open mesh floor. More than 50% of the brood was infected. The queen and all the frames were destroyed and the bees were united with a nuc. For as long as I’ve kept bees in Orkney there’s always been chalk brood and some years are worse than others. I’ve tried nearly every method under the sun to try and get rid of it, apart from spraying magic potions on the bees and frames if you know what I mean.
What doesn’t help in Orkney is our cold damp weather , our amm(ish) bees which are supposed to be more susceptible to it and our closed gene pool (no imports of bees to try and keep varroa out). So as you can see the dice is well and truly loaded in the favour of chalk brood up here.
Most of the bee books class chalk brood as a minor brood disease and most of the time things will improve over the summer. But it’s also capable of making a colony unsustainable. How much should we tolerate in a hive, a few cells per frame, a few dozen cells, 25%, 50% or more? I don’t have the answer but would I be wrong to call chalk brood the elephant in the room? I agree with other members of this forum that more research needs to be done on chalk brood and I think no public money should be spent on queen imports.

[mbc]

I am sure there is a large genetic component in it.


I'm sure there is also an age factor involved, with young queens generally tending to lay more robust eggs which turn into more vigorous larvae capable of withstanding more challenges.

[Jon]

Not so sure mbc. I have seen brand new queens mated in Apideas start off with far too much chalk brood.

[mbc]

Well yes Jon, undeniably some are susceptible from the start, but others get worse with age in my experience.

[busybeephilip]

I'm sure chalk brood is most likely associated with hygenic behaviour and has been with AFB - I bet someone has published something in relation to this.

Anyway, as "we" strive to encourage hygenic behaviour in the context of varroa then the only solution is to destroy the offending queen and logically, the drone colony's queen(s) that the offending queen mated with ?

If there is chalkbrood in your new apideas then it is partly due to the drone parental line as well as the maternal line

[busybeephilip]

Jon,

I think you should consider this article http://www.moraybeedinosaurs.co.uk/Varroa/chalk_heritable.html in relation to queen raising where emphasis is placed on the inheritance of chalkbrood and the implications that siblings will carry the disease.

If this is the case then the queen mother and drones being used to queen your apideas that show chalky brood may be carrying the genetics for chalkbrood. It might also indicate inbreeding ?

[Jon]

I don't see that much chalk brood, just the odd cell or two, but you always get the odd colony which has far too much.
I don't raise queens from colonies which have chalk brood.

Harbo and Harris have published papers on hygienic behaviour and the relation with AFB and Chalkbrood.


It might also indicate inbreeding ?

From your link


Contrary to the widely held view, no connection could be found between inbreeding and the incidence of chalkbrood. In actual fact reading from fig 4, the opposite of this trend appears to be the case.

[Rosie]

Didn't the link say that the inbreeding effect may have been an artefact because the inbred lines were more highly selected than the others?

[Poly Hive]

FWIW Bernard used to say it was more prevalent in damp cool springs and I have a vague memory that he mentioned Orkney in that regard. His suggested cure was to re-queen as he postulated it was a genetic weakness.

PH

[The Drone Ranger]

some years back I requeened about half of my hives with queens raised from my best hive in Spring that half all had bad chalk brood
I was sure it was genetic and the moral of the story was dont put too many eggs in one basket

On the other hand I have tried just requeening when a hive has had chalkbrood that didn't make any difference
In an earlier post I have mentioned other measure tried

When the requeened bees were shaken on to new foundation and fed the chalkbrood dissapeared
That hive has stayed clear this year

If I was to choose just one measure it would be make a note of any colonies with chalkbrood
The following spring shake all the bees onto new foundation and keep fed till wax is drawn
Without exception burn all the original combs dont try to save the brood or treat the combs

Dont waste money on the mycostop or other "cures" they dont work
There is no effective treatment
Now I only use wood hives so if the theory of warmth is correct then there should be less or no chalkbrood in Poly hives but as I havent read any claims for this it seems unlikely
The genetic disposition may well be true because the infective agent is present in the environment all the time and yet only some hives are affected
I wouldnt count on breeding from a queen that has no chalkbrood as being a safe route though because the queen that produced all the chalkbrood prone daughters had no history of any chalkbrood in her hive

Its a very under explored area you will see white fluffy mummies or smaller black mummies which as I understand it are the infectious stage
If your bees are prone to chalk they may do better on a solid floor with the hive tipped toward the front because it makes the ejection of mummies much easier
The fungus apparently needs two strains to be present for reproduction (that may be faulty memory please correct)
When it spontaneously just dissapears its fairly likely it hasn't really got fully to the infectious spore forming stage
Once combs have been infected by those spores though they are effectively useless (I feel)

Theres an article here but I'm not a member of Ibra so hopefully someone who is will give us the low down on their findings
http://www.ibra.org.uk/articles/Effect-of-type-of-brood-comb-on-chalk-brood-disease-in-honeybee-colonies

[Eric McArthur]

The Drone Ranger wrote:
[QUOTE=When the requeened bees were shaken on to new foundation and fed the chalkbrood dissapeared
That hive has stayed clear this year.

Len Heath did some sterling work on Chalkbrood some years ago.
Using his study assisted in the work mooted in the pasted link!



www.moraybeedinosaurs.co.uk/Varroa/chalk.htm

Professor Len Heath investigated the disease ... The CABA apiary bees exhibited negligible chalk brood this year 2008 and again the Open Day on 20th July ...

[masterbk]

I found that when I changed all the solid floorsto OMfloors the problems of chalk brood in colonies more or less disappeared and now I rarely see it (I had just one colony out of 28 colonies with a few cells of chalk brood it this year). I think researchers have found that Carbon dioxide is a trigger for chalkbrood spore germination so maybe the extra ventilation of the mesh floor reduced accumulation of carbon dioxide (produced by respiration of the bees) preventing chalk brood spore activation

[Jon]

I have a mix of open mesh floors and solid floors and I have never noticed a correlation with chalk brood and I do look out for those things. I have certainly come across bad chalk brood on colonies which are sitting on an open mesh floor. Proper data needed of course but I doubt there is any correlation.

[nemphlar]

I'm confused is Eric back

[chris]

I tried omf's and am now back on solid floors with a couple of 2 inch diameter ventilation holes. The reason I tried omf's was because of chalkbrood problems. It did seem to help clear it up, but I suspect requeening was the main reason.(Together with leaving insulation on in early spring.) I haven't had chalkbood colonies since going back to solid floors


I'm confused is Eric back


Yes, but he seems to have gone advanced at last:p

[masterbk]

Extensive review paper on chalk brood might be of interest to the more scientific beekeepers on this forum

http://www.bijenhouders.nl/files/Bijengezondheid/graaf/5.-kalkbroed-art-aronstein-2010.pdf

[The Drone Ranger]

It would nice if he was back in some ways even Grumpy was part of the choir.
Hi ho hi ho its off to work we go

[The Drone Ranger]

Heres a little clip of Eric McAthur's findings

"To cut a long story short I am convinced, despite all the science and scrutiny that has gone before that the explanation for out breaks of chalk brood has nothing to do with queen quality, genetic resistance or good house keeping on the part of the colony. In my opinion the disease is a condition of inadequate food and more specifically the dearth of income of nectar or the lack of liquid feeding. The application of the formic acid in the 2007 case I am certain was not of any great significance. But that is not to say that used hive furniture should not be adequately sterilised before use.
."

Now I can't say if that is wrong or right, but my experience is that changing queens won't fix chalk brood which agrees with what Eric says in his article
If you were starting from scratch with a new hive and combs etc a different queen might be more resistant
But replacing combs with ones sterilised by acetic acid wont work either which was part of the method used to fix the problem in Erics case
Also I am inclined to believe that if the chalk brood mummies are thrown out and the cells filled with sugar syrup the problem will dissapear for a while but I think as soon as those stores are uncapped there is every reason to expect it will return.

For all I know Eric has gone on to investigate this further and may have some new insights
I don't think he was trying to give a definitive answer to chalk brood just stimulating a debate
Heres the link http://www.moraybeedinosaurs.co.uk/Varroa/chalk.htm

[Eric McArthur]

I'm confused is Eric back

Be confused no more!

Eric

[Eric McArthur]

Heres a little clip of Eric McAthur's findings
[I]
For all I know Eric has gone on to investigate this further and may have some new insights
I don't think he was trying to give a definitive answer to chalk brood just stimulating a debate
Heres the link http://www.moraybeedinosaurs.co.uk/Varroa/chalk.htm
.............................................
Timeous syrup feeding in late winter, followed by solidly crystalised sugar in kilo bags over winter, then sugar syrup feeding from mid March till the bees are actually foraging on the first major early summer nectar sources has worked for me since 2007.

[nemphlar]

Good to see you back, always interesting

[The Drone Ranger]

.............................................
Timeous syrup feeding in late winter, followed by solidly crystalised sugar in kilo bags over winter, then sugar syrup feeding from mid March till the bees are actually foraging on the first major early summer nectar sources has worked for me since 2007.

Hi Eric
Nice to see you back on here
There is some work being done with leafcutter bees and a google for them and chalkbrood will turn up quite a lot of stuff
Unfortunately there doesn't seem to have been much progress on that front either as far as I can tell
They tend to go down the chemical route like in the PDF below
http://www.saspa.com/PDF/05.%20Chalkbrood%20Control%20in%20Alfalfa%20Leafcu tting%20Bees.pdf

[Eric McArthur]

Hi Eric
Nice to see you back on here
There is some work being done with leafcutter bees and a google for them and chalkbrood will turn up quite a lot of stuff

>>>>>>>>>>>>>>>>>>>>>>>>>>>

Many thanks for your kind words!
The work on Megachile has been ongoing for many years in Canada and the health successes are reassuring. Amazing how resilient these bees are - the industrial scale of the cocoon selection process is remarkable. The things we subject our pollinators too!

[Drummo]

Interesting to read peoples experiences on Chalkbrood.

I'm a novice beekeeper in Brisbane and I can give you an Australian perspective on this.

I bought a 6 frame NUC 5 weeks ago and new hive. I checked the hive after 2 weeks and all seemed fine. Prior to the inspection we had 7 straights days of teaming rain with higher than usual humidity.
The day after the inspection I noticed debris at the entrance to the hive, which turned out to be chalkbrood. The succeeding days saw more and more mummies deposited at the front of the hive, which I cleaned daily. The supplier of the nuc and hive has never had chalkbrood and the queen is only 6 months old so I have to assume the hive picked up the chalkbrood fungus from pollen in my area.
I was advised to increase ventilation to the hive, which I did by slightly raising the cover. After a week I lowered the cover again.
I did a 2nd inspection yesterday which was 4 weeks from hive creation. The floor of the hive was littered with mummies and debris. I cleaned off the floor as best I could without upsetting the bees too much.
There was no additional comb since the first inspection, ie the 4 empty frames of the 10 frame brood still hadn't been touched. I guess the bees are too busy with the chalkbrood to build any further.
There doesn't seem to be any more bees from the 1st inspection which I would have expected. There are however more bees foraging than at the start.
I've been told to sugar feed to stimulate the queen to lay more but haven't tried it as yet. I've also been told to use the banana trick.
I'm not sure what the best option is but if anyone has some suggestions I'd be keen to read them.

Cheers

[gavin]

Seems like you're in the same time zone as Neil! Welcome, Drummo.

First of all, I doubt very much that the previous owner saw no chalkbrood. It will have come with the bees and frames. You *might* have a queen with a propensity to chalkbrood, or the current problems might be exacerbated by something that's happened to them. Chilling is the thing that sets off chalkbrood. I wonder whether the process of making or shifting the nuc has left them depleted of bees? That would cause a slow build-up and difficulty maintaining temperature.

Try not to open them when it is cool and keep your visits short. Do feed them syrup to help them build. In the longer term, replace old frames. Assess in the months to come whether the chalkbrood is still excessive and if so then requeen f you can.

[Mellifera Crofter]

... I'm a novice beekeeper in Brisbane and I can give you an Australian perspective on this.

I bought a 6 frame NUC 5 weeks ago and new hive ... and the queen is only 6 months old ...

Six months or six weeks? If months she would have emerged some time in August when the average temperature (the internet tells me) is about 9C. Is it possible for a queen to emerge so early in the season? And if six weeks then you received her when she was a week old and would not have had time to lay a nucleus-worth of bees - so it would have been a put-together nucleus, and Gavin is probably right in that case: that they suffered from a bee shortage and could not keep warm. I'm just curious.


I was advised to increase ventilation to the hive, which I did by slightly raising the cover. After a week I lowered the cover again.

Over here people aren't to keen on raising the crown board to increase ventilation because you get cold drafts through the hive. An open mesh floor is better.

You're right - your post made me reread the thread again: it is interesting.
Kitta

[Drummo]

Thanks for the replies, the advice and the welcome :o

The guy I bought the hive from seemed like a very genuine guy. He has 3 hives of his own and has called me a couple of times since I bought the nuc to see how things are going. He said he had seen chalkbrood when a friend had it but hadn't had it in his hives and so couldn't help me much. He did suggest sugar feeding. He also said that he would give me more bees if I needed them.
I know that he put the nuc together in the afternoon and I picked up the hive that evening so yes it was a put together nucleus.

'Cool' here at the moment is a relative term. On both days I opened the hive it was 32C plus. I have only opened the hive twice.

Will start sugar feeding this afternoon and see how that goes.

I'll check with the supplier of the hive when the Queen was actually born but I think he said May, which would be the end of the season in Brisbane. The six months is wrong but that's just my inability to keep up with the fact that it's already 2015. I'm still stuck back in mid 2014.

Cheers

[gavin]

I know that he put the nuc together in the afternoon and I picked up the hive that evening so yes it was a put together nucleus.


If nucs are created in an apiary and left there many of the flying bees return home. You get a nuc with the house bees that were left on the frames, sealed and open brood, and most of the older bees gone with not enough bees (or nectar brought in) to keep everything warm. When I've made that mistake in cold summers :o I've seen chilled brood around the edges of the comb (or worse). Once I've made mistakes like that 2-3 times I usually get the message! There are things you can do to mitigate this: shaking in more young bees from other frames (doesn't always work, sometimes they go home), sealing in for a few days (ditto), moving the parent hive off to the side and putting nuc(s) in their place to catch the fliers, and/or taking the nuc away to a second apiary (you might have lost the fliers before you sealed them in).

Sounds like the guy you got them from was not that experienced. Feed them and they will pick up slowly. With any luck and given your climate chalkbrood may decline to an insignificant problem as the colony strengthens.

[Drummo]

Thanks Gavin;

What you've related seems to fit pretty well with my scenario. I know the seller had the nuc sealed in the new hive when I arrived so I'm thinking he did the right thing.

There were no more mummies yesterday so maybe things are picking up.

I have another query, I put sugar syrup out yesterday and the bees have shown no interest in it at all. I didn't want to open the hive so I've put it on top of the hive.
I put the syrup out again this morning and still no interest from the bees. I thought they would have been all over it. Is there any reason why they would ignore the syrup?
I used a half cup of water to a half cup of sugar.

[gavin]

Bee feeders are designed to be placed inside the hive, in an empty box. If you have an open container place it in an empty brood box or super but with floats of some kind to stop them drowning. Leaving it out risks encouraging robbing. G.