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Moldy Frames in Brood Box


We opened up our hive today. It has been a miserable wet winter here in the Midlands, England, with lots of flooding. The hive has been covered with tarpaulin, albeit this was after it got drenched. Now it has warmed up a bit and the sun is out, we have removed the tarpaulin and looked inside. We have 8 frames that all have green or white mold growing over them. I have looked this up and see conflicting advice, some say throw it all out, bleach the frames and start again, others say it’s fine so long as its not black mold, and the bees will sort it out as it warms up.

We started this hive (our first ever) last summer with only a few frames, and now all 8 are fully drawn. We located the Queen, she appears fine and busy, and each frame has some capped brood and plenty of capped and uncapped honey.

Any advice would be greatly appreciated!


Hello and welcome to the Flow forum!

Nasty surprise for you there! I note that you have done some research already, and found conflicting advice. This is typical in beekeeping, so don’t worry too much. :blush:

Should you remove the frames? Well, like many things, it depends.

  1. Is the mould just on the wood, or also on the wax? If just on the wood, you can leave them in there. I might wipe the wood down with a cloth soaked in 4% chlorine bleach, but don’t touch the wax with the bleach.
  2. If the hive was weak, I would consider removing the mouldy frames, if I had clean drawn frames or frames of honey to replace them with. You probably don’t have that option as it is your first year.
  3. If the bees are using the frames, despite the mould, I might leave them in place, especially if they have honey in them. They will clean them up eventually, but only as the number of workers increases. If they have brood in parts of the frames, I would definitely leave them there. The cells with healthy brood will already have been cleaned up by the bees. I would not want to discard their hard work if they are happy with their bee nursery.
  4. If the pollen frames are mouldy, I would toss them. The bees probably won’t use moldy pollen.
  5. From your description, it sounds like the mould is probably a species of Penicillium, which is quite common and pretty harmless. If it was black, I would suspect mildew, which goes with damp environments and is also pretty harmless. For reference: https://bg-bees.com/2016/07/21/mold/

Here are some other articles about mould in hives for a bit of perspective for you. Probably don’t apply to your situation, but just so that you know it is common:

If you posted photos of a moldy frame, we could tell to what extent the frames are contaminated with the mold… so that would determine your remediation approach. I’m in the camp where everything that shows mold is usually disposed of…in cases of minor mold presence, I might place the frames in a honey super on a very strong hive to deal with the mold.

In areas where moisture buildup over winter is an issue (like it is in Canada), it’s important to match the frames available for wintering to the bee population. Mold often occurs when too much room (too many frames) is given to the bees…they can’t control the internal conditions. Commercial beekeepers here typicall cram as many bees into a single brood chamber as is possible in the fall…there isn’t any comb unoccupied. Here is a photo of Ian Stepplers (commercial beekeeper in Manitoba, Canada) populations before winter…Ian has his own Youtube channel.

It’s a stretch to think a novice beekeeper can accomplish this without a few more years of experience…but it’s something to aim for…get your summer bee populations up and limit their wintering space…it makes such a difference in wintering results.

Here’s my daughter explaining our first spring inspection…the bees have been crammed into single brood chambers the previous fall. We haven’t seen moldy combs for a long time.

Dawn_SD has some good advice above.

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I’m in Tamworth :slightly_smiling_face:. Where are you? Loads of local clubs around you could take a frame to and get some advice.

Stick up some pictures. Is the mould just on the frames or on the inside of the brood box as well?

How strong is your colony looking? Sounds pretty typical after the type of winter we’ve had in the UK.

Like Dawn said mildew is nothing to worry about.
Circulating your frames is a good way to allow you to clean them and for the bees to create clean comb. Just make sure you do this when the colony is strong.