The symptoms indicate rust, a fungal disease that is quite common and widespread, with rose-family plant species (serviceberry, hawthorn, apple, crabapple, pear, quince, etc.) being the host plants it can infect where spores looking like this will be generated. Rust fungi are unusual in that they spend part of their life cycle in another plant entirely (junipers, in this case, like our native wild Eastern Redcedar) so the spores being produced now are moving back onto juniper and won't re-infect the serviceberry or quince. In spring, spores made on junipers infect these various rose-family species again to complete the cycle. This means that no fungicide applied now will have any effect. Treatment would need to begin early in the spring, but fungicides are not foolproof so infection might still occur, and their use could put pollinators or other organisms at risk, especially since spraying would likely have to coincide with bloom. While rust doesn't typically kill its host, the symptoms (if infections are severe) can be prominent and recurring every year, though the severity won't necessarily be the same every year as fungal infections can be highly weather-dependent.

You can pluck off and dispose of spore-producing fruits if you prefer, but given how tedious that can be and not very effectual in preventing infections in future years, there is no harm in ignoring them instead. They do not pose a hazard to wildlife (since birds normally relish serviceberry fruits) and the animals will know to pass infected berries by since this is a naturally-occurring disease in our region. Keep plant stress to a minimum by monitoring the plants for watering needs given our current drought.

Miri