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Black spots/mould? at end of honey flow channel


Ive been noticing in one of my older flow frames that some black spots are appearing.

Any thoughts on how best to clean it and why it has occurred? Just happing on one frame.

This is my third season beekeeping so that frame has been on the hive continuously since late Summer 2017.

Was thinking of bending the end of a straw cleaner with a fine bristle brush end and seeing if I could clean it like that.


There’s some related info discussed in this topic, not sure we really got to the bottom of the issue though? Maybe @semaphore has some further updates on the problem? Mine is OK this season since I’ve really kept an eye on condensation compared to last.

That looks suspiciously like common black mold to me. If it comes off easily with a wipe of say a pipe cleaner, as in a tobacco pipe, then take it as being mold.
As it doesn’t have much honey in it I would take it out of the hive, wash it out with warm water then soak it in a warm water/bleach solution for a few hours, wash it again, dry it with a hair drier on low heat then paint some melted wax onto the frame and refit it to the hive.

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Maybe it’s mildew? There is a difference though I would give the external parts a wipe with some household bleach as mildew will be cleaned easily. Additionally, you can wipe the internal part with a damp cloth by wrapping it around the flow key and inserting it and wiping it.


Thanks for the replies.

It’s taken me some time to get back in the super, but I did remove the frame yesterday and have attempted to clean the mood spots as suggested both on the hive and off it.

Those that can be reached wipe straight off.

The mold spots are ONLY at the end of the channel in the sections around the tube hole, which are recessed back and so almost impossible to get at. The bent over end of a pipe cleaner does work to some degree, but the gap at the top of the tube is very fine and so not easily penetrated.

I doubt these marks are propolis as I am not sure how the bees would get propolis in there but would be happy to be wrong, if anyone cares to disagree.

I have soaked the whole channel in a very mild bleach solution for 15 mins, then washed it thoroughly out, Then soaked the end in 50/50 apple cider vinegar and warm water.

Photo is post cleaning efforts. Hmm…

I just had a brain storm, what about trying a baby’s bottle cleaning brush, it is about the right size and fairly firm bristles.
Are the spots near the end where the tube slides on on the inside or the outside? Apart from there it all looks like you cleaned it up well.


So after chatting online to the honey flow team I decided to have a go at removing the wires so I could clean the end blade of the flow super and get at the last spots of mold that no brush I tried could reach adequately.

In preparation for this operation I watched Cedar in action in the videos contained in the following link…


I managed to get the bottom wire off but the top wire was tight so I left well enough alone and realised I could get my bottle brush in well enough with just the bottom wire removed. Was much easier than I thought in the end.

And it gave me a new appreciation of the elegance of this flow frame design. it truly is amazing.


Hi Rae, i have a similar problem. I live just south of the NSW/QLD boarder. I took apart a flow frame a couple of weeks ago and reconstructed it last weekend. I don’t want to do it again. I’ll try to upload a pic.

On the bright side it was very interesting and easy enough- it was the was wash that took for ever -it’s such a smart construction.

I don’t want to put the frames back in until I have resolved the mould issue. I have a couple of questions for flow -given the new to reduce mould and bugs (ie wax moth) generally - What is the best way to store frames overwinter? and will freezing the frames degrade them?

Goodness I managed to upload pics…now the bees…

Did the frames end up mouldy over winter because you left them on top of the broodbox or because you stored them elsewhere?

Wow, yours had a lot of mold. My sus frame was actually full of honey and full capped. It was only the end of the frame where the tube inserts in that the crevices some mold grew in mine. I think it was possibly due to me harvesting a frame that was not fully ripe/capped off. I had inspected, but somehow I inserted the key in the wrong frame and it was not until it was flowing and I got only one 1kg of very thin honey/nectar did I realised I’d tapped the wrong frame. I’m not sure if this is the same frame as I moved them around at one point and split waxed and clean new frames across two hives, but I have a feeling that is the explanation. No mold in any other frame in the hive or in the other one.

I find I get a steady harvest through winter where I am (south of Brisbane/Greenbank area) and I keep the supply high on the hive during that time, only taking a frame of two to give them more storage space as needed, especially after the winter solstice passes.

You can put the flow frames in the freezer by the way. I’ve not found any reference to storing them there but that is what I was thinking fo doing if I ever need to remove a super from a smaller hive.

Can only imagine with humid conditions and no bees to clean them that problems might occur…

I keep watching my flow supers, but it seems the bees fill them over winter too. My hive scales say the hive weight reduces for a few weeks, but bees seem active in the flow super all the time.
I wasn’t ever sure if the supers had to come off over winter or not, so far the Bee numbers were too big to reduce into one brood box.

With more hives at different strengths now, we will see what the next winter requires. A good rain season may bring up this mould issue around here as well.
No good rain season predicted, but we do get surprises and relentless rain for months, never mind predictions.

They were left on the brood box over winter.

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Ki’a’i One day I’d like to come and see your setup. It sounds interesting.

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That would be lovely Katarina. I’ll show you around the land of gnomes, flowers and honey on Mt Jerusalem.

I inspect the supers (not brood) on warmer/still days (in excess of 24 degrees) when I am concerned they are running out of room through Autumn and Winter and I can see there is a flow happening. I keep these intrusions brief, but it helps me to see what is truly capped and what is not, as I find the end frame is often not filled and the rest is.

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Wintering your Flow Frames is discussed a fair bit on the forum. Here is the topic:

You can search based on region as wintering advice will vary from region to region.

You can freeze the Flow Frames, and this is the easiest option if you have the freezer space in my opinion.

Here is a topic which mentions the condensation issue and then mould after leaving the Flow Supers on over winter when there wasn’t a high enough flow on.

Also the faq’s on our website:


I am dealing with a similar (much more minor) problem. Do you have any photos of how it turned out after the clean?

Also- how did you clean it? I am looking at sugar soap and a scrubbing brush at the moment and its very slow going!

Welcome to the forum, you will find lots of reading and good advise about bee keeping here.
If you are asking about the mold in the draining trough try some white cleaning vinegar and a bottle cleaning brush., with a final rinse of clean water and using a chux to soak up the water pushed into the opening with your ‘flow key’.

I would simply fill my utility sink with hot water and put some bleach in it and soak the flow frames until clean. Rinse the heck out of them and rewax them.I wouldn’t worry about food grade plastic being bleached, rinsed, dried and stored.

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