I know I’m opening a can of warms, but Feral non-treatment bees is a thing of the past!!!
According to DR. Samuel Ramsey, varroa destructor feeds on the fat in honeybees! Not the hemolymph! This is important because if you do nothing else for your bees you MUST treat for varroa! Especially in August to September time so your winter bees have enough fat to survive til Spring. This is 90+% of cause of winter losses!!
If you have low mite counts and the bees can handle it (there are acceptable thresholds for spring and fall), then that’s great. But if you have low or zero, it’s better that you don’t do anything – wouldn’t want to contribute to miticide resistance. Some people call letting their bees die every winter “treatment-free”. That’s not really fair to the people who are very educated and attentive and control mites while being miticide-free, which is what most of us mean by “treatment-free beekeeping”
There are many natural ways to deal with mites, including small hives that encourage swarming – this brood break disrupts the mite mating cycle. There are smoker fuels known to be disruptive to mites. You can dust your bees with powdered sugar to encourage cleaning. You can buy a strain bred for its hygienic behavior (cleaning, chewing open & discarding infected brood).