Is this a disease or bugs?

[Desirai]

I'm finding this mess on some of the plants in my yard.
Are insects doing this to my plants, or is a plant disease? It's on multiple plants.

Here are some pictures:

[rainbowgardener]

Couple different things going on. Bottom two pictures are leaf galls. They are caused by aphids, mites, or little wasps that lay their egg and induce the leaf to grow the swelling, which the larvae live inside of, protected from predators. They are common on trees and shrubs and often pretty harmless.

The top two pictures are something else that I don't recognize, some kind of mold, mildew, or fungus, I suspect.

[Desirai]

Thank you for that information.