The rust on the serviceberry is fairly common in our area. It is a fungi called Gymnosporangium libocedri. What makes it unusual is that the fungus reproduces using two hosts. In our area the rust likely originated with a cedar tree.
The rust is essentially an aesthetic problem, and in wet years will be worse. You can remove the affected foliage and/or apply chemical treatments for this season. The rust will not winter-over, though with the alternate host tree nearby, you may find it is infected most years.
Oregon State University Extension has several publications that deal with rust on serviceberry.
This is an overview of information about your tree: http://extension.oregonstate.edu/yamhill/sites/default/files/ww_serviceberry.pdf
Here's an OSU Gardening Tips article about rust: http://extension.oregonstate.edu/gardening/watch-out-rust-can-jump-incense-cedars-fruit-trees
This page from the PNW Plant Disease Handbook lists chemical controls. Only one is for homeowners, indicated by the H in a box. Follow label instructions. https://pnwhandbooks.org/plantdisease/host-disease/serviceberry-amelanchier-spp-rust
 

Thanks so much for the info!

I hope it works.

Rex

I have not looked up the label for this specific material, but want to caution you to read the timing of application especially well. A basic issue with leaf fungal disease is that the materials are applied to protect new foliage as it expands in the spring. It does not cure the leaves already infected. Some advice includes pruning a tree to a managable size for treatment. The problem comes if a tree is already large, your pruning options are limited because actual "topping" a tree damages it. Hiring a certified arborist is an option if your tree is beyond what you have equipment and skill to work with. Good luck. These trees are beautiful in spring.