Greetings from just across the border. ( I live in Elmira, NY, right on the PA border)
I believe I share substantially the same conditions you do in NEPA.
You can certainly keep bees without treatment here.
While some old men here don't seem able to decide whether it is better to believe research papers or experience, I just believe what I am observing.
you can succeed at being treatment free, but you will need to pay attention to both colony health and genetics.
I know it's true because I am doing it.
Of the three strains of bees I keep, all are very aggressive groomers.
The guard bees at the entrance sometimes groom returning foragers to prevent mite introduction so aggressively that at times it almost looks like they are fighting a robber to someone unfamiliar with their behavior.
Keeping colonies a little on the crowded side and having bees that aren't in a hurry to swarm at the drop of a hat ensures not only that most mites are groomed from sister bees efficiently, but also that the comb is well covered and they have no refuge from being found and attacked.
Keeping the hive well fed and busy promotes not only these densities on comb, but resistance to disease. (It's my opinion that parasites tend to attack sick/weak hosts first.)
No strain of bee, and no genetics are a silver bullet that will keep bees from dying of varroa if they are not properly cared for, though.
But healthy bees that are aggressive to varroa, and a strain that gets after 'em when they show up can succeed and thrive treatment-free.
The strains of bees I am using and where I got them are:
Local feral bees-
gathered from the wall of an abandoned house that had been continuously inhabited by bees for several years.
From Kale Luce at Russell Apiaries New York russellapiariesny.com
Northern Select Sunkist-
From Jason Varner at Russell Apiaries Pennsylvania russellapiariespa.com
Both of these men were quick to respond to communication and gave excellent customer service.
I suspect a fair amount of the success of all three strains of bees I am using derives from the fact that they are locally produced in our region.
Not only is their behavior in synch with our conditions, but in the case of bees I bought and had shipped to me, transit time was very short and so the queens' health was not subjected to the stress of a longer trip.
I know some might cite scientific papers or failures of others far from us;
all I know is what I am experiencing in the climate and flow conditions we both share.
You're welcome to pm me if you have any questions.