This is an updated and better put together summary of Finskis overwintering procedures :
note: temps are in Centigrade
WINTERING BEEHIVES IN FINLAND
Our bee summer is short. Willow starts blooming at the beginning of May. After 10.8 you may take all honey off . At the beginning of September it is last chance to feed hives for winter. So, if you take all honey off, bees leave with sugar 8 months. Main yeild wlow is from 20.6 to 25.7.
We have permanent snow from December to start of April. So wintering under snow is not a correct answer.
in Western Finland they often has only 4 inches snow. Most of beehives situate near sea cost, where worst winter temp are under -20C. But in inner land -30C in February is quite normal, but not continuous.
In April nights are often -5C and days +10C.
Essential part of wintering is to give formic acid or thymol fumigation to gives that it kills the mites which will otherwise destroy winter bees and their brood. Perhaps varroa do not kill the hive but it reduces more or less the size of winter cluster.
RULE ONE in wintering is that you must have a bee stock, which is properly sensitive to lengthening day and stops brood rearing at the end of August. If the hive continues brood rearing over November, it will die very soon. It consumes too much stores and is not in wintering mode to get over long winter. But no problem. We have good stocks of Italian, Carniolan and Buckfast bees which act properly in wintering.
RULE TWO in wintering is that you reduce the hive room to that size as the cluster will be. If the hive has 6 frames of brood, it will need 6-7 frames for winter. If hive has 15 frames brood, it needs 2 boxes to wintering. No one uses 3 boxes in winter.
Professional prefer wintering colonies in one box. They use to keep excluder over first box and that is why colony needs that one box.
NEED OF SUGAR
Colonies spend on average 20 kg sugar during that long winter. Consumption increases rapidly when the colony starts brood rearing.
Cleansing flight use to be in March and up that no extra feeding can be given to hives.
HIVES AND WRAPPING
All hives are insulated. They are double wall ply hives or polystyrene. Polyhives are more and more numerous.
Wrapping is not needed. It is just old habit. Some like me use geotextil covering to protect entrance against snow, wind and birds. Woopecker are sometimes harm to polyhives.
If you use mesh floor, the no upper entrances are open.
If you use solid bottom, upper entrance or some upper hole should exist that respiration moisture comes out from hive.
In normal frost, like -10C, condensation happens often inside the hive. It makes there snow, but when mild weather comes, it melts and drills to bottom and out from hive. A solid bottom is little bit in slanting position that water comes out.
Starvation are quite rare in insulated hives . Varroa makes losses, if not clear dead outs, but at least reduction of clusters. Nowadays varroa has made bad surprises even to experienced beekeepers. It has became more lethal for its viruses. 20 years ago varroa was easier.
SPRING BUILD UP
After cleansing flights bees continue wintering as long as they get pollen from nature. If the colony has pollen stores in frames, they can start early brood rearing but others must wait that willow starts blooming. Patty feeding is used very seldom but most beekeepers believe that sugar feeding helps in early build up. But it does not.
Insulated hives and proper ventilation keeps hives warm. In warm hives, which are fully occupied, the build up is faster that in hives which have much room and too much ventilation. 15 W electric heating has shown that colonies really need warm hive to make large brood areas. Very few heat with electric but more believe that good ventilation helps build up. Again, beekeepers have lots of belief.
It depends, how big the cluster has been after winter. According that the hive will be ready to forage surplus. Small winter cluster and rapid spring build up is a dream. It is impossible. You can help small colonies to become productive when you give frames of emerging bees from bigger hives. It helps in swarming problem too.
Varroa is nowadays a main killer of winter. It reduces so much size of wintering cluster that before winter the whole cluster may disappear from hive. But more often is that it kills 20 -30% from cluster and makes spring build up slower.
European Union Varroa Group researched best treatments in years 1998-2006.
Recommendations were that give formic acid or thymol treatment in August and then in November give a oxalic acid trickling. Autumn treatment kills about 70-80% of mites and trickling should handle the rest. If you give trickling too early, hives may have brood and mites are in safe under cappings.
Hives have many kind of winter losses what ever you do. I have had 20% spare hives during my beekeeping decades and that has been fine.
Most usual are
- queen losses: drone laying, missing, decreased laying, nosema stops laying
- nosema reduces bee cluster
- varroa reduces bee cluster
- weak hives must be joined to get proper build up
- a hive dies if it continues brood rearing in autumn. But those are rare and thanks to our local queen breeding. We do not use package bees.
It is normal procedure to feed hives in spring if it seems that hive has too few stores.
Emergency beefing continues sometimes up to June. Frost nights will be over 10.6.