We don't have any apple trees, just peach and figs, but
NCSU has a list of resistant varieties: Some
varieties are resistant to apple scab, powdery mildew, cedar
apple rust, or fireblight. These include Redfree, Prima,
Priscilla, Jonafree, and Liberty.
Logan's sells a
copper fungicide that can be diluted then applied with a sprayer, plus it is organic. I've used it on roses to tomatoes, but it does leave a blue hue on the plants.
I've tried using an old timey cornmeal solution for rust on my hollyhocks, however it was really messy and unsightly, so I just remove the leaves since they are already diseased.This
UW Ag extension claims that simple pruning can keep your juniper's disease free too.
My in-laws managed to snag me a copy of the NC Master Gardener training manual, it's about 4 inches thick and very helpful! Most of the information leaflets can be viewed online and are available as PDFs to print or save:
http://www.ces.ncsu.edu/depts/hort/hil/