Ick! Mold in my hive!

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 has overwintered with little interference from you. What you find in there is not gleaming combs of honey and pollen, but empty cells rimed 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!”

But wait; let’s back up. Molds (or moulds, which seems 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 to sprout.

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.

Now 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.

A mold spore in a winter hive believes it died and went to heaven.
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 believes it died and went to heaven.

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.

The problem with mold is that we, as pampered humans, apply our own standards to the beehive. 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 is slow to mold and why a little vinegar or lemon juice in sugar syrup can delay mold for a while.

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 don’t 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 the bees the last laugh.

Rusty
HoneyBeeSuite

Comments

Beekeeper Eric
Reply

“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.

Cheers

Rusty
Reply

Eric,

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.

nanacoug
Reply

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.

nanacoug
Reply

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.

Michelle
Reply

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!

Rusty
Reply

Thank you, Michelle!

Alia
Reply

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.)

Rusty
Reply

Alia,

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.

michelle
Reply

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.

Rusty
Reply

Michelle,

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.

Michelle
Reply

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 :-)

Rusty
Reply

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.

Michelle

Thank you so much. Michelle :-)

Gary Fawcett
Reply

Hi Rusty,

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 :)

Thanks

Gary

Rusty
Reply

Gary,

I’ve been called worse.

Higgie
Reply

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.

Rusty
Reply

Higgie,

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.

Higgie
Reply

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.

Hannah VW
Reply

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?

Susie
Reply

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,

Susie

Rusty
Reply

Susie,

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.

Gary Fawcett
Reply

Hi Susie,

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.

Gary

Cyndi
Reply

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

NinetyEight
Reply

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?

Thanks.

Rusty
Reply

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.

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