After some more research, I think these are aphids? There are a lot of ants on the tree too.

Last week we started spraying spinosad for fruit flies. It sounds like that might be bad for controlling the aphids, by keeping their predators away.

It looks like you have Black Cherry Aphids. 

There are many aphids that will feed on cherry trees. Biological control is basically just spraying them off. Unfortunately we havent had any rain to do this for us so I recommend getting out your hose and spraying them off. Any insect ice will also kill beneficial insects that are feeding on them. 

https://pnwhandbooks.org/insect/tree-fruit/cherry/cherry-black-cherry-aphid

https://extension.umn.edu/fruit/growing-stone-fruits-home-garden