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In Finland 90% out of hives are Italians. They are kept even on Polar Circle. Average winter food consumption from September to May is 20 kg.
I have had numerous Italian strains 45 years. I had 10 years Carniolans together with Italians.
The quality on Italian strains depends totally on you, how much you make breeding work and try and select the queens of different sellers.
If you do not take care on continuous selecting, after couple years you have typical mongrels, even if they are yellow: Swarmy, protect their best, inbreeding problems, average layers, average honey yields.....
Same with Carniolans. The chance to get bad material is bigger than in Italians.
And then to keep on you good material is the biggest job
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To keep on non swarmy stock is bigger job than prevent swarming with AS, - in small apiary. But 100% swarming is a nuisance. With hybrid Carniolans I have got 120% swarming, and AS method did not work very well with them.