I did some research and found that these malformations are caused by mites. They overwinter in the trunk of the tree or a nearby tree and move int the new foliage in the spring. The malformations are a form of a gall, which is a growth on a tree, in this case on the leaves. The mites move onto the foliage in the spring. Although unsightly, they do not harm the tree. I believe the type of mite you have  may be Eriophyid. I am sending you a link on galls. I hope you find it helpful. Thanks, Jeanine

https://extension.colostate.edu/topic-areas/insects/insect-and-mite-galls-5-577/