Notes on leaving flow super over winter

I have a hive that has now had its flow super on it for two winters. Last season at the end of autumn the frames were half full of honey- over winter the frames remained uncapped but half full. In spring the bees finished them off and I harvested…

This year I harvested them at the end of autumn and they went into winter empty… since then no honey has gone in and bee activity is low. Now the frames are damp with condensation on the view window. And the frames have gone a bit black with- I assume- mold.

It seems last winter the honey protected the frames from damp as it kept the bees interested in maintenance up there- fanning, ventilating etc? Also maybe the antibacterial nature of the honey itself helped keep the frames clean?

So maybe if you are going to leave a super on over winter: make sure it’s (at least) half full of honey?

I’m going to remove it tomorrow. Has anyone had darkened frames and how did you clean them. I’ve seen darkening like this before in other flow frames after winter. I’ve also seen it in wooden brood frames. It’s not that pretty

The colony seems perfectly good down below. It is a 3 story- Nuc tower hive- 10 brood frames and 3 flow frames. The flow super has an entrance at the very top- and the hive has a mesh floor.

This is the one:


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Guess in your narrow tower, condensation hits the top big time. Most of my hives consist of 8 frame broodbox and flow super on top. Over winter, the flow supers are 30 to 80% filled.
I leave the supers on, as we do get some nectar coming in. Right now it’s the first time I see the bees digging into their own sources and loosing a bit of weight. But some trees seem to be budding up. Wish I knew what they are. Some eucalyptus. Not long now. Looks like we are going to get an early flow.
Never saw mould bits in the super.
Maybe with the narrow height of your tower, you could add some ventilation half way up?

I don’t think it’s the shape of this hive as I’ve seem the exact same in 3 if our 8 frame flow hives. I really think it was that the super was empty at the start of winter.

So much talk of buds and flows soon- I hope things are tracking the same here in Adelaide. I moved 6 hives to the hills a month ago- I’m super hopeful there is an early and strong spring up there. It’s a sweets spot- organic fruit orchard that backs onto a national park with another national park nearby. Lots of melaleuca, gums, blackberry, cherry, apple, pear, walnut, hazelnut and many wild flowers. I heard some of the gums were flowering recently. I got superb dry capped cut honeycomb from there in autumn.

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Hi Jack here in Perths hills there is national park all around and fruit trees in every back yard. Minimum 1/2 acre blocks, what I thought would be a bees paradise, somewhat proven by the amount of feral colonies around. My friends down in the badlands, errr flatlands way out perform in honey quantities. Quality? I think our honey is better but don’t we all…
I am leaving supers on two colonies here but have drained half the stores. Prior to draining there were few bees. After draining the bees went to work in numbers. It amazes me how they pack down.
Mould in most of the boxes here, only on the walls though. I’ll probably spray the removed supers with vinegar but aren’t conscerned with it. Who knows perhaps it’s beneficial? :wink:

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Hi Jack I left my flow super on and with 2/3 capped honey in 3 frames and bit less than 1/2 capped in remaining 3 frames. As you know @Semaphore I live at Semaphore (That will confuse some) so I agree with you on the empty frames being a possible issue.
Photos of condensation today at 11:00am and video of winter foraging today (11C /52F). Looks like the dry winter will continue into Spring in South Australia.


Howdy Cobby,

That’s exactly the condensation I see in the hives. I’d be very interested to know if yours come out of winter without the black mold. I reckon they will- and I reckon it’s the presence of the honey that is saving them. From now on if my super is empty at the start of winter I will remove it.

Today I noticed my bees bringing absolute masses of pollen- light yellow- big balls - a steady stream- really a lot like mid-spring. I just noticed one of your bees returning with similar looking stuff in you video. I wonder if it’s the same thing? I have to move that hive tomorrow- just 2.3 Km’s - I’m hoping that’s going to be an OK distance…

In fact- in five minutes I have to uplug this computer and move it too. And the table it’s on. And everything else. Why am I on this forum?


Quite a few flowering gums around at the moment I have seen white, yellow, orange and deep red pollen last week or so. I will follow up on mould when I start opening up the brood nest 3rd week of August.
Hope the move goes well for you, still in Prospect?

I did have condensation problems in first year with water literally running out of the roof space through the hive.
Caused the hive to weaken considerably and mould coved just about everything inside.
My Solution:
I leave the top board vent covered in mesh (which the bees open or close from time to time) and put a 25mm (1") hole toward the apex of each roof end. My roof was “re roofed” with aluminium flashing which extends far enough out for the holes not to be weather affected. Todate no further condensation problems. I think there are photos somewhere in this forum.

There are plenty of other fixes for condensation.


I’ve gone for a vented lid this year. I’ll be interested to see if that makes a difference. Last year I had some red mould appearing, no black.

I’m on the flats near good tracts of bush land and a plethora of fruit trees in backyards. I took your approach last year and again this year (drain about half the honey, come back in spring) but I leave the hybrid on so I essentially drain the 3 flow frames and leave the 4 standard frames. I reckon if I opened the hive now I’d easily be able to harvest at least two of the flow frames again. Unfortunately the rain deters me (my bees seem to handle cooler weather better than high winds - they get cranky with high winds if I open the hive).


I’m in Croydon Park- it’s only 5 minutes from where I was.

Today I removed the super from my hive and was surprised to find the central frame completely full and capped. And another frame 50% full and one 100% empty… This experience proved my theory completely - the frames are blackened wherever there isn’t honey- and perfectly clean wherever there is. There is no evidence of mold on the capped wax. It obviously mold proof. After harvest those sections will be clean- everywhere else will not.

Last year my brother had this black mold in some outermost frames edged- he hoped the bees would clean them up in spring but they didn’t really, the filled them many times over the season but the frames still look a little mucky.

I’m not sure it matters but I certainly would prefer clean looking frames.

The next step is to figure the best way to clean these frames? Any one have any ideas? I tried blasting one with a high pressure cleaner- it helped a bit but was not as effective as I hoped. I’m figuring I’ll soak them in warm water- and some agent to clean the mold off. Is a bit of bleach a bad idea?

I’ll take a few photos when I get a chance.

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From what I hav heard in general the Adelaide suburban plane beats the hills too. Our hills also seem like bee paradise- but for whatever reason harvests up there can be patchy. Apparently many years they get bugger all… I guess the great diversity in urban gardens guarantees good forage all year round. Also it’s a lot warmer on average.

I’m hoping that maybe my hills site is special- and will buck the trend. I’m sure it will! I have hopes that there will be big flows from all the gums every so often… the honey from the burbs is lighther and very butterscotch- the hills one is darker and burnt molasses.

I had seven hives in my urban backyard- but it was a jungle and they dissspeared into it- now I’ve moved I think I’ll only have two… or three… and the odd Nuc maybe :cowboy_hat_face:


I have left two flow supers on two 8 frame brood boxes over last two winters with no mould problems. The bottom brood boxes have solid floors but the lids are the “ migratory “ type with four 20 mm holes covered with fly screen in each one. They are also very productive. I think the extra ventilation at the top prevents mould.


Bleach is amazing at removing black mould but (I believe) we are still waiting advice from Flow about whether or not it (sodium hypochlorite) has a deleterious effect on the plastic.

The next step is to figure the best way to clean these frames? Any one have any ideas? I tried blasting one with a high pressure cleaner- it helped a bit but was not as effective as I hoped. I’m figuring I’ll soak them in warm water- and some agent to clean the mold off. Is a bit of bleach a bad idea?

We had some questionable ‘darker’ cells in some of our empty flow frames after a condensation heavy winter last year. The previous winter (2016) we left the super on with no such condensation issues but the bees seemed to store more honey in them that winter and also the hive was in a spot receiving more sun but had to be moved to a less favourable position due to an unhappy neighbour.

Anyway, it was a little fiddly, but last year we took the frames with darker cells out in early spring and washed them in warm water with a very diluted detergent and used a manual method (stainless steel straw cleaner brush poked in) to clean up the affected cells. Then gave the frame a good rinse and dried it out before putting back in hive. Lots of wax stayed intact in the cell gaps so the bees didn’t have to start from scratch. The frames came up nicely and haven’t had the problem again this winter as I’ve managed the condensation a little better with ventilation.

Did you literally have to poke your brush cleaner into each and every cell? :sleepy:

Yep :expressionless: but it was only the columns of cells towards the ends, rather than the ones in the middle of the frame that seemed to mostly affected…and not all frames, so it wasn’t tooooo bad a job.

I have some frames where it’s all over. Won’t be fun. How many thousands of cells per side?

I’m gonna see if I can figure something easier. I’ll try with my high pressure cleaner again too.

I agree, that would be madness to manually clean that many cells. Maybe a soak then the high pressure cleaner will do the trick?

A few people on the forum have tried different cleaning techniques:

I remember @busso put them in the dishwasher which seemed to help the Flow Frames, but left a big lot of gunk in the machine.

Our Cleaning/Sterilisation faq has been updated on our website:

I know it refers to a few other things other than mold, but thought you might find the chemical information useful anyway.

Under normal conditions, it is not necessary to clean your Flow Frames (click here for information on routine cleaning and storage of Flow Frames).

In some jurisdictions cleaning may be necessary prior to sterilisation as a means of disease control—please contact your local department of primary industries for region-specific advice.

Cleaning and wax removal for sterilisation

Following are some options for removing wax and propolis from Flow Frames. We have tested these treatments and found them to have no effect on the mechanical function of the product.

Prior to treatment manually remove excess wax, by placing the frames on newspaper and scraping. We have achieved best results at wax removal by disassembling the Flow Frame prior to treatment, however, please note that this will void your warranty.

These are maximum exposure recommendations and should only be used under conditions where sterilisation of the frames is necessary. Do not exceed temperature and time for optimum function of your frames. Destroy all debris by burning.


#Ethanol is highly flammable. Do not heat ethanol on or near a naked flame.
*The use of casutic solutions (Caustic Soda/washing soda) requires great care and caution. You must use suitable protective clothing, protect your eyes and use rubber gloves.

The safety of your bees is very important—after any treatment of your frames please ensure they are rinsed thoroughly in water and dried prior to storage or returning to your hive.


Please note that if you are treating AFB this is a notifiable disease. Legal requirements differ between jurisdictions. Please contact your local authority for advice on appropriate disease control measures.

Bleach treatment:

In some jurisdictions, it is acceptable to use bleach to sterilise AFB contaminated hive components. Research has shown that immersion for twenty minutes in a solution of 0.5% sodium hypochlorite kills AFB spores and other bacteria. The solution must be in direct contact with the spores. It is, therefore, necessary to remove wax and other debris prior to sterilisation (see above cleaning options).

Gamma Irradiation:

In some countries, Gamma irradiation is used to sterilise equipment infected with American Foulbrood (AFB). A dose of 10 kGy is sufficient to eliminate AFB spores (Hornitzky&Wills, 1983; Australian Honey Bee Industry Biosecurity Code of Practice, 2016, Pg 11). Flow Frames can withstand a maximum of 20 kGy Gamma irradiation, above this, the plastic will become brittle and the mechanism may fail on harvest.

What you should do when treating with irradiation:

Flow Frames should be exposed to a maximum combined dose of 20 kGy irradiation. This enables 2 rounds of AFB sterilisation at 10 kGy. Some Irradiation facilities use beehives as ‘gap filler’ in larger loads. This means a single round may expose your frames to more than 40 kGy.

We recommend you contact the facility to discuss maximum doses. If you are in Australia (excluding Tasmania) we recommend that you send your frames to Steritech’s Brisbane Facility. This facility is capable of controlling the irradiation dose. If you need to send your Flow Frames for irradiation please mark them clearly for future reference.