Hi Michelle,

That is  rust on the fruit of your serviceberry.  Eastern red cedar (Juniperus virginiana) is the alternate host of several rust diseases. While there is nothing you can do to control the infection that is already on the serviceberry fruit now, you can try to mitigate future infections. Rust overwinters as mycelium in gall tissue on junipers. During warm, rainy spring weather, gelatinous horn-like protrusions emerge from the gall. Teliospores produced on the horns germinate and give rise to another spore type, basidiospores, which are carried by wind to fruit or leaves of the broadleaf host (in your case serviceberry).

Do you have any eastern red cedars on your property? If so, you could elect to remove them or locate and destroy any cedar galls on them by April 1, before the spore-producing tendrils are formed. That would help mitigate the rust, but even doing that may not eliminate it completely on your serviceberry because there are a lot of eastern red cedars around! 

Marie