Couple more questions. You say "dont separate double boxes". Do you just hit the center seems if the cluster cant be seen from the top. Do you do any type of a spring treatment?
It is often said that take upper box away from douple brood. But it is impossible. Mostly boxes are glued with burr. You get open with with force, but them you have thousands of bees between 2 boxes and you must put them back.
When you put syrup in seems, it will reach the bees. The cluster will expand too for disturb and they will get dirty for oxalic syrup.
Nowadays Finnish beekeepers give quite often spring treatment aften cleansing flight before the hive start brood rearing.
.Finnish and Finnish. There are lots of beekeepers which are afraid of use oxalic acid. .
However, it only treatmen which can be used during winter, and then the hive is broodless.
I tried to manage with one treatment in a year (oxalic) but now, after some years, I have seen that it does not work.
Mites do often their dirty tricks allready in August when the hive rear its winter brood.
Two treatmenst are quite necessary: formic acid or thymol in August and then oxalic in winter.
Varroa has become more dangerous than 20 years ago.