...and how do I get rid of it?

I think that is rust. Need a fungicide but which one I don't know. If you have cedar trees nearby they are a host for rust and will infect the apple trees.

Good luck with 'em!

Very probably cedar-apple rust.  You're not going to get rid of it unless you also get rid of the cedars.

Here's what it looks like on a cedar:

There are some cedars around, but the closest one is maybe 100yds away. This just started showing up last year.

So spraying won't get rid of it?

You have to start spraying with a good fungicide (I use Immunox) before the leaves start budding out, around here it's usually in March. I spray every 2 weeks all spring until it starts drying-out some with just the Immunox up until all the blooms are done on the trees, then I add the Bonide fruit tree spray which also has pesticide, miticide etc. in it. I wait until after the blooming so as not to kill the bees/pollinators. The Immunox is a fungicide only and doesn't hurt the bees, plus after it dries good a couple hours it's water resistant and stays on the trees for the 2 weeks. The spores come from cedar trees up to miles away, tending to cedars close by may help ever so slightly but you're not going to eliminate the risk. Here in Tenn. cedars are everywhere !!!