Not to worry, they are harmless galls.
Galls are abnormal growths of plant tissue caused by insects and other organisms. Gall-making parasites release growth-regulating chemicals as they feed, causing adjacent plant tissues to form a gall. The parasite then develops inside the gall. Several different groups of insects and one family of mites have developed the ability to induce plant galls.
Galls come in an endless variety of forms. Many are strikingly colored or curiously shaped. If your tree is covered with them there might be some source of stress that you should investigate. The Sick Tree Treatment is the best cure if you want to improve the health of the tree.
Tony M

Forget the Sick tree tripe.

They are galls from gall wasps. They are not parasitic in any way.

Now you can turn that into a