Junipers and red cedars hold the disease. If you have red cedars with-in a quarter of a mile or so, you got a source of rust.
I have some roughly 50 year old mcintosh trees in the hudson valley, thy get those spots. But they keep trucking on.
The best bet is to buy disease resistant varieties. I try to buy them, but I also buy trees to make cider. You can make cider from disease resistant vraieties, but I have some specific classic species I wanted. Hrarison, roxbury russet, golden delicious., and granny smith. Forgot if hewe's is CAR resistant or not. Just need to spray anti-fungals a few times in the spring. Some trees get hit hard, some less, and some varieties show no effect. I have a spot near canajoharie I can hunt and plant trees alongside the fields and have trees at a cam pni the adirondacks. They'll all disease resistant varieties. Mostly kerr, redfield, and nursery specific crabapples.
Common ones liberty, enterprise, kerr, freedom, and many others. My little patch I have liberty, enteprise, empire, trailman, franklin cider, chestnut and crabapples like droptine, crossbow, big dog, 30-06. all winter hangover. Many nurseries have their own specialty varieties. Even members on here have their own, like signal fire.
Big box stores have liberty in NY. I believe red delcious varieties have resistance too.
I planted some antnovka bareroots last year, their first roun of leaves were riddled with rust real bad. Thought a few wouldnt make it, The 2nd round of leaf grrowth that 1st year cleared righted up.
Make sure you cage those white cedars. I didnt in 2017 and they got gobbles up in no time.
