Mold seems to be the topic of the week, but that is not surprising. This is the time of year when you open a hive that overwintered with little interference from you. What you find there are not gleaming combs of honey and pollen, but empty cells rimmed with white, green, blue, or yellow mold. At least it looks like mold and smells like mold. And you are right—it is mold.
Beginning beekeepers often respond by separating mold and bees as quickly as possible, treating everything with bleach, or kicking themselves for being incompetent. If all the bees are dead, mold is often fingered as the cause, as in “Mold grew everywhere in my hive and killed my bees!”
Mold in hives is natural
But wait; let’s back up. Molds (or moulds, which seem more sinister) are tiny fungi that live on plant and animal material. They thrive in humid conditions and reproduce by forming spores—great clouds of spores. These light-as-air particles are everywhere, just waiting for the right conditions so they can sprout.
Bee hives provide the perfect place for mold growth, supplying all the things molds like best: debris from plants and animals, a moist environment, and darkness. Millions of spores are waiting in the crannies and crevices of the hive with napkins tucked under their chins, knives and forks at the ready. They know the feast is coming.
Larger colonies have less mold
An active colony of bees has no problem keeping mold growth at bay. The bees clean and polish brood cells, remove dead bees, rotate stores of pollen, and remove invaders. But during the winter, the colony energy is spent in a cluster. The main interest is survival—eating and keeping warm. Housekeeping is put on hold.
As the winter progresses, the cluster becomes smaller and the bees move up through the boxes, eating their way through the honey stores and leaving empty, unattended combs behind. The mold gleefully takes over.
To make matters worse, a layer of debris accumulates on the bottom board or screen—vast helpings of dead bees, mites, bits and pieces of comb, feces, drips of honey. The mold is beside itself with happiness and joy. It reproduces like crazy. A mold spore in a winter hive thinks it died and went to heaven.
A growing colony will remove mold from your hive
But as spring approaches and the colony begins to expand, the now active bees begin regular housekeeping duties. The dead are hauled out, the cells are polished, and all that mold disappears in a flash. The bees know what to do.
On the other hand, if your colony died, it died of something else and then the mold took over. Excessive mold is the result of colony death, not the cause of it. I’ve seen beekeepers discard everything in sight just because of mold, which is silly and wasteful. Mold is a natural part of the entire beekeeping process.
Don’t apply your mold standards to bee hives
The problem with mold is that we, as pampered humans, apply our own standards to the bee hive. In our own lives, we go to extremes, even buying food laced with calcium propionate, sodium benzoate, and potassium sorbate so little furries don’t start on our dinner before we do.
These chemicals are usually acidic substances that delay mold growth. Most mold doesn’t do well in acidic conditions, which is why honey (very acidic) is slow to grow mold. It also explains why a little vinegar or lemon juice in sugar syrup can delay mold for a while.
Use bleach as a last resort
If you can’t stand the mold and simply must do something with those combs before you give them back to the bees, put them in a warm and dry environment for a few days with plenty of space between them. This will stop the active growth phase. Some people like to spray with bleach. Bleach is okay but if the combs don’t dry out quickly, the mold will just grow back. Sunlight discourages mold growth as well, but be careful not to melt your combs.
I recommend just leaving moldy frames with the bees. If you check those frames after the colony has a chance to work on them, you won’t be able to tell them apart from any other frames. Applying your own standards of housekeeping to bees will make you crazy and give your bees the last laugh.
Honey Bee Suite
“Leave it to the bees” Good advice! Have to be careful how much you leave for them though, and the type. At the most, I’ll let them clean up 1 frame with a palm sized patch of fuzzy, soft mould. More then that and the bees will spend too much time cleaning, and if the mould is dry and hard the bees will have to tear down the comb to remove it, and then rebuild – time better spent making honey, dealing with varroa and brood diseases, and getting ready for next winter.
I suppose that a case for moderation can always be made. Then again, I think 5 or 6 frames of moldy comb is moderate. The bees are going to clean and polish all the cells anyway, so the mold is not much extra work. And even if they have to tear down part of it and rebuild, that is more energy efficient than secreting all new wax, something that requires egregious amounts of food resources.
This discussion has been sooooo helpful. I do think that I will give my two bottom boards a vinegar wash. they are really gross. I have almost 40 frames of comb and comb + uncapped honey that have mold here and there. I set them on end and aimed a fan one at a time at each to try and dry them out. They are in the garage and high temperatures in Seattle are still well below 50 so not much evaporation is occurring.
I have almost 40 frames of comb and comb + uncapped honey that have mold here and there. I set them on end and aimed a fan one at a time at each to try and dry them out. They are in the garage and high temperatures in Seattle are still well below 50 so not much evaporation is occurring.
I love this. I’ll say it again, as a newbee, I’ve learned more from reading your blog than I ever learned from the beekeepers in my association. Wonderful stuff, really, Rusty!
Thank you, Michelle!
What about full frames of honey (from a dead hive), covered in mold? I’m too scared of mycotoxins to eat it, but would it be safe to feed it to another hive? (Pretty sure the hive was empty because they absconded, I’m not worried about poison/disease.)
I’ve never heard of mycotoxins on moldy comb honey, but that’s not to say it couldn’t happen. At any rate, I’ve eaten moldy comb honey where I’ve tried to clean the mold from the comb and it wasn’t pleasant. I’ve also tried extracting from moldy comb and that wasn’t too good either. That musty flavor/scent gets right in there. However, I’ve given moldy honey comb to bees with no ill effects on a number of occasions, so I believe your bees should be fine with it.
Hi, I’m a new beekeeper. I checked my hive for the first time last week and found 4 frames of mould. I removed it straight away as I thought it would be bad for the bees respiratory system. Should I put it back in the hive? Please help as i have not been told this might happen.
You say you found four frames of mold the first time you checked the hive. I’m confused. Was this a nuc, a full colony, or a package? It seems strange that mold would collect in a brand new hive, unless it is an overwintered hive that you got from someone. I need to know that before I can give you an answer.
Hi, sorry I wasn’t very clear. I got a nuc last year and they were fine through the year. When I went into the hive for the first time this year there was 4 frames of mold. No one on my bee course told me of this. I do live in co. Kerry Ireland so it is very wet here. Thanks Michelle 🙂
The mold grew on the frames in the winter while the colony was small and the bees in the cluster were unable to tend to it. As soon as your colony starts building up a little, put the frames back in the hive and the bees will clean them up for you.
Thank you so much. Michelle 🙂
We found the hives with quilt levels over our wet winters, didn’t have any mold after last winter. So guess the increased ventilation helps.
We mentioned this article in our latest podcast http://kiwimana.co.nz/19-mouldy-bee-tongues/.
Sorry I called you Randy on part of the talk, it was late and night when I recorded it 🙂
I’ve been called worse.
One of our hives died didn’t make it through the winter, likely CCD since there is no evidence of bacterial infection. We would like to add the honey super to our existing hive which is healthy and happy. As you recommended, we left the moldy frames to be cleaned by the bees. We also noticed some black mold on the wood of that box & wanted to clean it out before reusing it. I’m wondering your thoughts on reusing the super from the dead hive.
Also, you’re a great resource, Rusty. Thanks for taking the time to share your insights.
The mold is no problem. If CCD killed your hive, you would want to disinfect before using any part of it. More likely it wasn’t CCD, but maybe Varroa or tracheal mites or queen loss, in which case it is fine to use the super. What makes you think it was CCD? Just curious.
Naivety. It’s our first season. We eliminated a lot of variables including intrusive mites and are still unsure of one direct cause. Perhaps I should amend my previous statement of “likely CCD” to “fear of CCD.”
Thanks for your prompt response! It’s great to have your experienced feedback.
I know this is an old post but looking for advice, I am new to this:
My hive died over the winter and the areas with the dead bees on the frames molded. I just cleaned out the hive and brushed out most of the dead bees (some are stuck in the wax in the frames). How should I clean and store the hive and frames (moldy and not moldy) until I am able to get another nuc soon this spring?
Here’s a post that may help: What to do with moldy combs.
I have a freezer full of mostly capped honey from my hives that didn’t make it last winter. Problem is my husband unplugged freezer and didn’t tell me, so have moldy frames so ugh!
What do I do with the honey? Frames? Just extract throw away honey and let bees clean the comb?
Why extract it? You can just give the frames to the bees for winter feed. They will clean up the mold and eat the honey. For them, it’s a non-issue.
I failed with my bees this winter, 1 hive out of 6 survived. The other five hives consisting of a total of 70 frames of honey have some mold and a lot of honey. I don’t know what to do at this point. Do I store the frames? (where and how?)
I’m getting 2 new colonies in 2 weeks. Do I put some of the frames in the new hives? How long can I keep the frames full of mold and honey sitting out? Right now they are all sitting in my basement where it is cool and dry. I’m afraid I’m going to get mice and or ants if I don’t do something. I’ve been doing some reading and research but haven’t been able to find help for my situation.
Feeling stung and confused,
I would put as many of those frames on your new (and old) hives as possible. The bees will clean up the mold in no time, and with all that honey they will get off to a remarkable start. The mold is nothing to them, so don’t worry about it as far as the bees are concerned.
It is the uncapped honey that usually gets moldy. In the future, you can turn the frames upside down and shake hard and most of it will fly out. Then, if you have a colony, you can give them the frames to clean up. It is easier to let them do it than to try to do it yourself.
Also, mold grows best in dark, cool, damp conditions. Store frames in dry, warm, and well-ventilated locations. Strong sunlight helps control mold as well.
Well the first thing I would determine is why the hives died? You say you have lots of honey, so it can’t be starvation. Unless the honey was too far away from the cluster?
Was the cause of death something like AFB (American Foul Brood)? Or Varroa mites?
This will help you to determine what to do with the frames and hive boxes from your deadouts.
If it was AFB, I would burn the gear, we have too in New Zealand by law. Your local laws will probably vary.
As for mouldy frames I would cut out the mould and reuse the frames.
Good luck with your new packages.
Susie – I’m going with Rusty on this one – and frankly, everything else she’s ever said. Unless your hives stink to the point your eyes water, you don’t have AFB. AFB smells like rotten meat and I’ve never yet met a person that couldn’t smell it. I live in the Seattle area and have trouble with long, wet, dark and cold winters. If I lose my queen or my bees can’t keep warm enough – I sometimes lose a hive or two and in spring find mold along with some capped honey. I just give the hive bottoms a good sweeping, wipe the mold, if any, off the top of the bars and dump in my new bees. They clean up the mold, rebuild broken comb and basically have the entire hive ship-shape shortly after they finish chewing the queen’s candy plug and release her. I did finally make a change to Carniolan over my beloved Italians. Carniolan seem to handle the long wet Pacific Northwest winters better but they are swarmers if you don’t keep an eye on them! Best of luck. And don’t fear the mold! Cyndi
Our Tanzanian hive died this winter and is in for repairs. There is quite a bit black mold on the follower board and the hive interior. Are you suggesting that we ignore it or do a little bleaching or junk the hive entirely?
If you junk every hive with mold, you will never have a hive. Mold is a fact of beekeeping life because you have living organisms that respire in a closed environment. Clean it up with a little bleach and call it good.
This is soooooo helpful. I have a top-bar hive with a window and saw some mold on the comb. Now that I know this wonderful information, I am happy!
By the way if you ever get a top-bar hive, during the summer the window is filled with bees and comb. But as winter comes you start seeing less and less bees in the window until you virtually don’t see any. That happened to me, and I thought they were dying off. But actually they are in a ball much smaller than I thought they would be in.
Just wanted to save someone from worrying to death about their first wintering top-bar hive.
I like this site because the information never seems to be out dated and its timely. I noticed some mold, very little I might add, in my hive. Now where to go for answers? I plugged it in my search engine and your site came up first. Well wonders never cease!
After reading your input, I felt a whole lot better. Yes, let the bees sort it out.
Thanks, Steve. Nice compliment.
Really like your blog. Very helpful.
A thousand thank you’s!!!! We are new, just opened our hive to find mold and started to freak out! This article told us to relax so relax we will!! You’re the best!
Any advice on empty honey super frames that have some mouse droppings on them? They are drawn out from year. Will the bees disinfect them, do I clean them (how?) or throw them and order new ones? Thanks much! Great articles and I appreciate your advice.
I scrape off anything obvious and then let the bees clean them up. They polish everything before using it, and the honey has antibacterial properties.
Thank you for this advice even if a few years old….. I’m a beginner and inspected brood box and found a few cells in two foundations with mould after reading I Will leave for bees to deal with but a QUESTION PLEASE, how to eliminate damp? In NZ, We have come out of a wet Spring and now into Summer, still it’s been a very wet one even last week it rained considerably and warms up on odd days so I’m assuming damp rises and has got into hive for mould to appear, is there anything I could do to eliminate this? I’ve cleared away grass growth and nearby Manuka branches (but they were not hanging over at all anyway) hives are placed on a pallet so off the ground in full sun (when it’s out that is) but we have had some cold evening spells. Would I best to put polythene under the pallet to reduce damp rising? Thank you in advance. Shona
Interesting question. I’m an ace at winter damp, but summer damp? Not so much. I would say to use a screened inner cover to increase ventilation, but maybe someone else has an idea. Anyone?
Moisture box might work
Once again, I needed some bee info and I was led to your blog for answers! I’m trying to save one of my hives. It was a new package that sprouted a mighty large crop of mites mid summer. We treated with Api-Var, but because it wasn’t a very big colony yet, and I think it did more harm than good. The treatment killed a large number of bees, so they were small going into winter – only covering 5 or 6 frames. I put a box of wood chips on top (our version of a moisture quilt) and hoped for the best. When it warmed up here in January (we’re in Lynnwood, WA) I went outside and couldn’t see any activity, even though my other hive was out and about enjoying the day. I suspected trouble, so I insulated the hive and put some dry sugar on the top bars. I didn’t look any further because I didn’t want to break the cluster. Here it is February, and another nice day. Lots of dead bees on the bottom board, and no one taking the bodies outside. I saw just one or two bees near the entrance. So we looked inside and found 4 frames with bees clustered at the very top right under my wood chip box. There weren’t 4 frames full of bees, just 4 frames that each had a few hundred bees. If I were to guess I would say they would cover 1 frame if they were spread out. I also found that they still had uncapped honey and pollen, but a lot of mold. Most importantly, I saw the queen! She was hidden in a cluster of bees, but I could see the paint dot on her back so we know she’s still in there. What do you think is our best course of action at this point? I have a habit of making things worse by trying to help (usually when the bees have it under control on their own and I interrupt their plans!). Thank you, and happy overwintering. 🙂
Apivar in mid-summer is likely to kill bees, because it gets too hot in the hive. When you use it, make sure you follow all the temperature parameters they list on the package.
You have wood chips for moisture collection, but it sounds like you don’t have enough ventilation. You need both if you want it to stay dry in there. A build up of mold sounds like the moist air is not able to leave the hive. The first thing I would do is make sure air is moving through the hive from the bottom to the top. Either add ventilation above the quilt or put an upper entrance just below the quilt.
That queen needs to raise brood asap, so make sure the pollen and honey are close to the cluster so the bees can access it easily. If you get a day up in the 60s, you might consider adding a frame of bees from your strong hive to give this small cluster a little population boost.
Just inspected my hive this afternoon. Dandelions have just popped in my neighborhood. Opened the hive and found a lot of mold in the brood super. I am using a Langstroth and overwintered my first year hive in two 10 frame deep supers. I saw the queen in December on a warm day winter inspection in Connecticut.
I could not find the queen today and I always see the queen. I remember providing the bees with pollen patty and stopped giving it to them over the summer because the pollen party was getting moldy and I saw that the bees were storing the moldy pollen patty in the pollen frames. I think this caused a lot of mold growth and now I cannot find my queen; I think she may have absconded.
There were no signs of eggs or brood or capped brood. I feel like if the queen hadn’t absconded, there would be a lot f brood. What do you think? Could the bees abscond due to mold from the open patty that they had stored in the cells? The workers are bringing in a little pollen.
They are fanning more than normal and that is a sign the queen is gone
A queen will not abscond all by herself, and since the bees are still there, they did not abscond. Now, the queen could have left with a swarm, and all the fanning could indicate that a virgin queen is out on a mating flight. Or it could mean that it is hot inside the hive and they are trying to cool it.
Mold does not kill bees and does not kill queens. Mold spores are everywhere all the time, but they only grow when conditions are right. Mold growth is the result of poor conditions in the hive, not the cause of poor conditions in the hive.
Is your hive getting enough ventilation? I would check on that first. If you don’t start seeing eggs very soon, you may have to purchase a queen.
‘They thrive in humid conditions and reproduce by forming spores—great clouds of spores.’
In an affected hive clouds of AFB spores are released by the cell cleaning crew – is this not also how they further spread, assisted by air flow from wingbeats or temperature differences causing a chimney effect, all over the insides of the hive i.e. the hive’s airflow being a major vector in the spread of AFB spores by dispersing these on the hairs of the cleaner, nurse and forager bees moving about in the hive?
Some spores are more apt to be airborne than others, and I don’t know the situation with AFB spores. I’ve never heard of clouds of AFB spores. Usually they are transmitted through direct contact with contaminated bees, honey, pollen, and equipment. Not all spores are created equal; some spores are designed to catch air currents and some are not.
Given that there could be, according to various sources, a billion or more from one cell, they are very small and so could likely to be readily airborne. I believe that this, as a dispersing vector, for AFB, has not, at least I have not been able to find on the ‘net, been examined.
My hive died over the winter. I went through and cleaned the hive today (removing dead bees, dusting off mold). I have 13 frames with from the broad chamber with honey and some mold. Can i store these in my freezer since i am not getting my new hive for a month? Will freezing them hurt them? How about honey with mold?
This is really, really confusing to read. Your hive died, but today you cleaned the hive, to get ready for a new hive, which you are going to put in the old hive. Did I get that right? If you remember that a colony of bees lives in a man-made structure called a hive, it clears things up. Your colony died, but your hive still exists.
1. Yes, you can store the frames in the freezer, but you don’t need to.
2. No, freezing them will not hurt the frames or the honey.
3. No, freezing the frames will not hurt the honey with mold either.
Hi Rusty –
It is good to know that I don’t have to panic due to mold in my beehives. What I am concerned about is that there is a glassy shine on some of the frames. Is this a sign of disease?
Also, both my hives died this winter – all the bees and honey in the brood box were GONE when I checked earlier this spring – not even any dead bodies. There were bees going strong entering winter so I am mystified as to where everything went. With no bee bodies to inspect, I can’t really determine the cause of the hive death.
Any ideas about what to do about the glassy sheen in areas or about what could have happened to my bees? Thank you!
Often “no bees left in the hive” is a sign of varroa infestation. The bees get sick with viruses and one-by-one they fly out of the hive to die. One at a time, hold an empty brood frame in front of you with sunlight at your back. Tip the top of the frame away from you so you can see the “roofs” of the cells. Look for white deposits. If you see them, then mites is the answer.
The glassy sheen is probably from propolis or insect secretions. I wouldn’t worry about it. I’ve seen it too and I just ignore it.
PS. I live in the Portland area where it has been very wet and cold for the last 8 months.
Thanks Rusty.. is there a danger of reinfestation from the mite residue left behind? It did freeze here.
Mites cannot survive without bees so once the bees are gone, the mites are gone. It is common practice to reuse equipment after a mite collapse, and I’ve never heard of any problems from doing it. The bees will clean up any mite feces and polish the cells before reusing them. Mites are very clean like that.
First. Thank you for all the info. This is the most informative site I have found. Second. I feel much better about my mold problem, although I do have a couple concerns I hope you can help me with.
I am in Montana and we had a very hard winter with over two weeks of below zero weather. Had a nice day in January so I cracked open the hive. With two full brood boxes going into winter I was shock at how light and easy to move it was. Still had a big colony and filled the feeder full of sugar and also a pollen patty to get them to warmer weather so I could start feeding syrup. Checked hive today and the whole colony has gone down far enough that they all fit between two frames. Its been two weeks and it doesn’t look like they ate any syrup or the patty. This is also my first year. Do I have a problem or will the colony bounce back when things start blooming?
Thank you so much for your help!
Your colony should have been building up in the past two or three months, not shrinking. I can only guess from here, but I suspect you may not have a queen. Until you can check on that, get some feed in contact with the small cluster. It is too small to keep things warm, so the food will have to be right there. The best place is just above them, but really close—touching close. On the first warm day, take a more thorough look.
Will moldy syrup hurt the bees?
A little mold in the syrup won’t hurt the bees, especially if they are feeding from the bottom, as in a jar or pail feeder. If they are feeding from the top, they may not be able to reach the syrup. You can retard mold to some extent by adding a little lemon juice, vinegar, or bleach to the syrup.
We are new beekeepers in Melbourne Australia (Down South). We find your blog extremely interesting and thank you for your obvious expert advise. We’ll be checking in on a regular basis.
Congratulations of a great site
Rob and Sam
Rob and Sam,
Thank you so much! Love hearing from so far away.
Reading through the above questions and answers, I’ve learned much. My question about mold is slightly different. We left the racks of honey in the supers for the bees for the winter. However, the colony died. Noticing robber bees visiting the hive on a sunny day in February, I removed some racks from the super. There is a light dusting of mold on the outside wax covering the honey. I removed the wax and tasted the honey. It’s delicious! Is it dangerous for us to consume this honey?
It sounds to me like wax bloom instead of mold. Did it smell like mold? In any case, beehive mold is similar to bread mold…harmless unless you’re allergic to it.
Thank you Rusty. We decided to eat the honey. We’ll be getting a new package of bees in April. Happy that I’ve discovered your blog.
Thank you so much! This has been so helpful to me also, I too lost my first hive over winter. I will start again with the newly ordered bees in April. I have a lot of mold and some of it knocked off my fames when I dusted it off. I’ll leave the rest for the new bees to take care of.
Has anyone tried vodka to kill mold on box interiors?
Very helpful cheers for the text.
Hi, I live in NZ and I own just one hive. This winter most of my bees died, I got left a very small colony. The hive now has two boxes of almost all frames with mouldy honey and pollen. What should I do? I don’t want to remove all the frames as there’s plenty of food for them. Thank you
You can remove much of the surface mold with a spray bottle of bleach and water. Let it drip off and then put the frames where they can dry. Once dry, just use the frames as they are. The bees will clean up the rest of the mold themselves. Mold is a natural problem in the bee’s environment and so they are very good at dealing with it.
Writing from Australia, and l’d like your opinion on extracting honey (from a flow hive) when 20% of the frames have mould. In a few weeks 80% of the frames will be capped and ready to harvest, however where the cells have mould the bees are avoiding it! They are empty.
Prior to summer I noticed the mould and cleaned what l could and gave the frames back to the bees to do the rest. It looks like they try, l see them in there, however they don’t use it.
Should l discard the honey or can we eat it?
I would taste it and then make a decision based on your findings.