Cherry tree pests

[Steve Z]

[Jungle Jane]

Its rust,I get this on some pear tree leaves,the growth on the underside of the leaves are the spores that can help it spread. Try & remove what you can although some leaves could be quite high. If you cut out the orange leaf bits early they don’t grow that big mass of spores.

[ameno]

Are you 100% sure those are cherry leaves? The shape and colour look a lot more like apple or pear. Cherry leaves are usually bigger, thinner, less waxy, and with more pronounced veins.

In any case, that's a rust fungus. Those lumps are the fruiting bodies. However, these fungi have very specific host species, and as far as I am aware, there is no such rust which affects cherries. Pears are the common one, and there is one which affects apples, too.

If the infection is mild, remove and bin or burn any infected leaves. If it's more severe, just leave it. Removing the leaves will do more harm than good (although you should collect them up and bin them when they fall).
These rust fungi need another (coniferous) host to complete their life cycle, anyway, so an infected fruit tree will not directly lead to more infected fruit trees next year.