Parks - I can't speak for others, I can only share my personal experiences & studies, some of which may be only relevant to my location.
I chose to be treatment free from the start, as recommended by my beek mentor. In 2015 I captured 2 swarms, split them once each to get 4 hives. All of those hives died by mid 2016. Cause of death was disease(s) due to Varroa.
My studies (compressed) - At this point I began to study bees in depth. Here's what I learned:
The 2 large/commercial beekeepers that I hold in highest esteem are:
Michael Bush -
www.bushfarms.comRandy Oliver - scientificbeekeeping.com
I've read everything on both gentlemens' websites. Well worth the time imho. To my view, both men have arrived at the same place - treetment free genetics - using different paths to get there. Both men offer incredible knowledge on this subject. I highly recommend studying their work.
We are very blessed to have Mr Bush posting here on Beemaster.
Timewise, Randy is well behind (Mr Bush) - and only has part of his Apiary TF currently.
I read somewhere - that India made a government decision not to treat when Varroa hit the country. They suffered a 96% to 99% loss of their bees. However, within 2 years their entire country was back to full production capacity. See - only the bees that were able to survive, were left to breed colonies from. India has never allowed treetment, as I understand it - and doesn't need it.
Africa did not treat their bees when varroa hit - with similar results to India.
In 2017 (I think it was) Randy Oliver tested (via alcohol wash) all of his 1000 commercial hives. He found 20 hives that did not require treetment - that's 2% of his total apiary. He immediately began to use those hives/queens as breeders & drone producers. Last I heard, he had 200+/- treetment free hives (and growing) in his Apiary, and intends on being 100% TF eventually.
The one difference with Randy Oliver's approach that I observed, was that he chose to keep his remaining hives alive via treetments, as he grew his TF apiary.
So, to my view & studies, there are 2 main approaches to achieving a totally TF apiary:
1) buy or capture a large number of hives & go TF immediately. Create your queens and new replacement hives from the ones that survive. Don't be at all suprised if you experience losses from 70% up to 99% (maybe 100%) in the first 2 years.
Or
2) start with a smaller qty of hives. Monitor mite counts via alcohol wash. Treat the hives that are going to fail - they will give you honey, wax, pollen, and bees for use with you other hives. Create queens from your lowest Mite count hives - until the day comes that you apiary self sustainable and 100% TF.
Small/Natural Cell size & clean comb (foundationless) definitely can't hurt the likelyhood of success in either one of the options listed - they will probably greatly increase your chances of success.
Back to my story - In Feb 2018 I got more bees. I chose the 2nd option this time - so that I don't spend all year "hoping & wondering" if I'll have bees next year. I currently have 10 hives, all from captured swarms & resulting splits. They are doing good. Right now, I seem to be observing an improvement in mite counts, and overall health of my hives - not because of treatments, but because of genetic selection. It will be a long process - but I'm not going anywhere, so we'll see ...
Note 1: some people have gone totally TF in one shot and their bees are still surviving - I completely believe them. That absolutely did NOT work for me, and many others also.
Note 2: when you raise daughter queens from successful TF mothers, the daughters will have offspring with [potentially] only 1/4 TF genetics - unless you can control the drones that your queens breed with. So if you can't control the drones, it may take longer to achieve true TF.
Note 3: I treat with OAV - only when/if needed, and nothing else.
I only post all of this in the hope that it will help someone.