I found some instructions for you... There are several fungicides on the market that are used to treat rust. They rely on oil, copper, sulfur or even baking soda as their active ingredient. Unfortunately, once the rust is on leaf surfaces, fungicides limit only the spread of the disease. If you want to actually prevent its appearance, you have to begin spraying before it appears and continue spraying throughout the growing season. Do this as often as every seven to 10 days. Because this can be very time-consuming, there are other options to consider. * At the first sign of rust, remove infected leaves and toss them in the trash, not the compost pile. * Water the base of plants with care to avoid splashing the foliage. Wet leaves can encourage the arrival of rust. * Provide good air circulation around plants, especially those near walls and fences. * Disinfect pruners with a mild bleach solution when pruning plants prone to rust.

Be sure to carefully rake up and dispose of any affected foliage when the time comes -- the spores can overwinter rather easily. And it might not hurt to consider a dormant spray next winter. Otherwise, there's not much you can do to control the problem now. Rust is seldom a fatal condition - pretty much just cosmetic in nature.

I am not sure what fungicide my arborist used on my serviceberry, but it worked; the injections worked better than the spray. If you already have affected berries, I would guess that it's too late for treatment this year, and the birds just won't eat the berries. The arborist has done the treatments on mine before the tree leafed out, so late March, as I recall. When the tree got the fungicide injections, the birds cleaned every single berry off the tree, so I guess they didn't mind the fungicide.

Neem oil is not a preventative. It is only effective if applied when the mites are present. Spring seems the time when they are most likely to occur so you need to start monitoring for them now.