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British Beekeepers Association Official Forum 

  • Mildew inside WBC hives

  • Beginners forum, ask beekeeping related questions and get help from other experienced beekeepers. Please use the Search Feature please to avoid duplicated threads
Beginners forum, ask beekeeping related questions and get help from other experienced beekeepers. Please use the Search Feature please to avoid duplicated threads
 #1649  by Jules59
 06 Jan 2019, 22:35
This is my first post and my first winter with my 2 WBC hives (both hives I built his year).

I recently noticed that mildew has started to grow on the inside of the gabled roofs and also on the tops of the crown boards.
It is usual for mildew to develop in winter ?

I had placed rectangle of insulation board (Kingspan) on top on a eke above the crown board on each hive as it seemed a good idea. Each Kingspan board has a 8cm diam hole in the middle "for ventilation".
Could the insulation in some way affected the ventilation within the hive?
Ive removed the insulation as a precaution.

The bees themselves seem OK, with plenty of stores in the supers (which I placed above the brood boxes).
Ive also recently treated with Oxalic acid trickling as one hive had a high varrora count.
 #1650  by Alan_A
 07 Jan 2019, 08:50
Hi Jules

I'm sure you will get some great advice from the more experienced beekeepers on this site but I think your problem might be the top ventilation.

I'm in my second year beekeeping and also have 2 colonies in WBCs that I built myself, the hives have open mesh floors and no top ventilation, this allows for natural convection within the hive where the warm air rising in the centre spreads out at the top and cools as it runs down the sides to repeat the cycle, that's the theory anyway but it works for me.

This autumn I made insulated perspex crown boards (see details on "The Apiarist" website) and it means I can observe my bees without opening the hive and from what I see the bees are perfectly happy in a cluster at the top of the brood box (I'm under supering) but most importantly there is no condensation. Hope this helps.
 #1651  by Jim Norfolk
 07 Jan 2019, 11:25
As Alan says its the ventillation. Warm moist air leaves through the hole in the top and condenses on the cold underside of the roof. Can I suggest removing the eke unless you have fondant in it and seal up the 8cm hole in the Kingspan insulation. Ideally the insulating cover should be sealed so any air exchange is through the floor. The water vapour can then condense on the cold mesh floor and drip out. Presumably the WBC has vents in the roof to help it dry out.
 #1652  by NigelP
 07 Jan 2019, 12:36
Ventilation has no place in winter beekeeping.
Shut down the hole and your mildew will disappear and your bees will thank you for not having to survive all winter living in a cold draft of air sucking all the heat from the cluster.
 #1653  by Patrick
 07 Jan 2019, 13:05
Welcome to the Forum Jules!

Nothing to add on the ventilation front, aside from reassurance for those possibly wondering about open mesh floors that as long as you don't have a hole at the top as well, they should overwinter fine - at least in the South of the country..

Impressed to hear both you and Alan built your own WBC's. Nuff respect. Used to be quite commonplace people building their own hives and plans used to be in many "how to do it" beekeeping books, but has become much rarer these days. Hugely satisfying I should imagine.

Don't forget the DIY and equipment section, if there are any tips you think worth sharing from your experience of having done it.
 #1655  by AdamD
 07 Jan 2019, 17:02
My view is the best way to configure a beehive is to consider the bees natural nest site of a hollow tree and try to emulate it. A tree will not have a (thin) 5 mm piece of plywood above the brood-nest but several feet of timber insulation. At any time of year, if a colony has a porter bee escape above them, they will block it up. They simply don't want ventilation above them and will seal up gaps. They prefer an entrance below the brood-nest.

As has been suggested, insulation should go directly on the crown-board, maybe the eke or something heavy on top of that to keep it there and snugly connected to the rim of the crown-board and the bees should be fine.

Another way of insulating WBC's (and I should try it myself sometime!) is to fill the cavity between boxes and lifts with dry leaves and then pile a foot of leaves above the crown-board. Perfect natural insulation that will disperse in spring once the lifts come off!

Alan - I once had a polyhive with a clear plastic crown board; condensation would appear within a minute or two of taking the poly roof off; otherwise they were condensation-free.

And, welcome to the forum from me.
 #1662  by Jules59
 08 Jan 2019, 23:24
Thanks everyone. All really useful advice/suggestions. I can see now that Ive probably created the problem by making a chimney (through the Kingspan) for warm moist air to rise up through to the roof space where condensation is taking place.

The eke was placed above the crown board to allow fondant feeding through one of the crown board holes.

I'll make new Kingspan tops with no holes.
 #2017  by Jules59
 20 Feb 2019, 09:49
That worked - thanks. Mildew stopped getting worse. Will clean up the mildew when I do a spring clean. Ive made some new crown boards so I can simply replace them along with the boxes and clean them all at my leisure.
 #2020  by Chrisbarlow
 20 Feb 2019, 12:14
That's great to hear you got the issue sorted.
 #2026  by MickBBKA
 21 Feb 2019, 00:10
Matchsticks under the corners of the crownboard could stop the chimney effect through the centre of it...……………………………………… CALM DOWN...……… I WAS ONLY JOKING :D :D :D

Cheers, Mick.