Mold on comb? Too cold to do anything about it, Michigan, USA

I’m in Michigan middle of winter. Has been not as cold as usual and I would say wetter than usual. Finally starting to see consistent temps in the 20s (F). When I looked in the window I have seen condensation on the inside of the window especially on a warmer day. Added dry sugar on a warmer day to maybe suck some of the moisture. Yesterday in the window I can see some mold (I think) on the comb. It’s white. I’m really thinking I can’t remove the frame due to temps until it’s warmer. Anything to do about this? Hive sounds good to me when I tap it, nice and loud. Window is on the bottom box, they tend to stay in the upper box.

With those sort of temperatures there is not a lot you can do other than try some ‘tricks’ to keep the hive and the colony warm. Wrap the outside of the hive in black plastic so that it will soak up the heat would help. Also if your hive has a top board that is closed off some wood shavings or sawdust can help to insulate heat escaping.
I’m not sure if the white you are seeing is mold, which is more often a mauve or gray color. A photo would help those in your sort of climate to give better ideas.

Yea I’m not sure why I didn’t post a pic. I’ll take one tomorrow.

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Hiya Marcos, did you leave the Flow super on over winter?
Knocking on the hive isn’t really best practice as it breaks up the cluster and the colony loses heat causing them to expend more precious energy to regain that warmth.

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Maybe knocking isn’t the right word? I just tap it with my knuckle with my ear directly on the box. I don’t think I’m breaking up the cluster though?

No I take off the flow frames for the winter. I have them in two 8 frame deeps which is typical for my area.

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@skeggley thought the same as me, but it sounds like you took the frames out and left the Flow box itself on? I’m in PA where we get cold winters too - I take off the whole Flow super, box, frames and all, and store it. I don’t know for sure if the box with all its cutouts is less suited for overwintering, but I guess things might get complicated in spring when the bees start raising brood in there.

For now I think the advice you got is good and I hope your bees keep chugging along to spring! :rainbow::blush::+1:

Ok, I reread your post and realized you said the stuff you saw is white - made me think of guanine, or excrement that is left by varroa mites. Please do post a pic for us… even if you don’t see this kind of evidence it’s highly likely they’re in there. Let us know if you need any treatment tips.


One potential solution that may or may not work is to put a ventilated/insulated ‘quilt box’ on top of your super. These seem like a good idea in cold and damp environments- and apparently work well to reduce moisture build up:

I intend to make some of these for my own hives over winter.


Moisture quilts are helpful - but you’d have to wait for a very mild day, say above 50 and no wind to put one on this winter or you’d risk chilling the cluster and losing a lot of bees because the moisture quilt goes on top of the top brood box and under the inner cover. People typically put them on as part of winter prep no later than October.

Hi Marcos,

While I am only new to bee keeping, I have been devouring every bit of information I can get and in the process, came across this video which might be helpful. Basically, the bees should be able to deal with the mould as shown in the video.

Hope it helps, cheers,

Sorry took so long and even so the pic quality isn’t great. Hive still sounds loud despite negative teens F (-40F wind chill) last week.

Hi @marcos, thanks for posting the pic. I do see the mold you’re talking about, plus the white stuff that might be recrystallized sugar syrup, if you were feeding that to the bees and some leaked and dripped down from being stored in cells??

Other things about your pic I am curious/concerned about and want to point out:

  1. Is that your Flow super or are you using a box with an observation window as one of your brood boxes? If it’s your Flow box, plan on not using it for brood or overwintering again since it needs to house very specialized gear and would take an extra beating from winter weather, plus create another task in spring that is pretty disruptive to the bees (removing all those frames and putting them in a new brood box so you can use your Flow frames).

  2. Either way, it looks like the wood is raw and absorbing moisture, leading to mildew on the exterior and possibly a reason there is excess moisture inside the box & causing the mold near the sugary places. Or did you seal it with something and maybe it’s not apparent in the picture? Or maybe you sealed it and the water is getting in because of the window cutout…back to question 1 :sweat_smile:

Anyway, if your bees are still kicking in there, cheers :+1: and you’ve got a new season to learn from and enjoy very soon!

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They had lots of honey. I added dry sugar but not syrup.

My flow frames are put away. It may be the box or it’s another that I have with windows. I wanted to be able to see in in the winter but I’m finding it’s not super helpful and just causes anxiety. Next year I’ll save the windows for the summer.

I seal the outside each spring with tung oil. I don’t do the inside. And it’s been 10 months since the outside was done.


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