Barbara said:

I believe you are correct. I tried to do a search on the web for apple
diseases before I read your post. Indeed I have 5 junipers about 50-60 ft.
from the tree, I haven't checked them for galls yet. Also, the apple is
Jonathan, a susceptible variety. The junipers are well established and way
too big to pull out, would spraying the junipers and the apple tree be
sufficient to control/get rid of the disease?

I think you are going to have to consider spraying. Maybe think about
planting a replacement apple that's more resistant. Pruning out any galls
on the junipers before they mature and produce spores would probably be
beneficial.

This page has some of the best pictures of the different phases of the
fungus life cycle that I've seen so far (including the growths on the bottom
of the leaves), as well as lists of resistant varieties and fungicides.

http://ianrpubs.unl.edu/plantdisease/g1327.htm

--
Pat in Plymouth MI ('someplace.net' is comcast)

Any technology distinguishable from magic is insufficiently advanced.
(attributed to Don Marti)