Q: I haven’t seen this before on my amelanchiers. What do you think I have here?
A: It’s cedar-hawthorn rust. I have it on my amelanchier (serviceberry) too. Spores travel between the two host plants and cannot survive unless the two hosts are fairly close to each other. There are junipers or cedars somewhere in your neighborhood and they have elongated, slightly swollen areas along the branches that were orange and gooey when rained on in spring. These are one stage of spore production. The spores infect hawthorn or amelanchier fruits nearby, causing the orange “horns” you see.
Not much can be done except remove and destroy the serviceberry fruits. If you do have juniper shrubs in your own landscape, examine the twigs for swollen areas and prune them out.