Eriophyes sp.
Small, irregularly, serrate, roughened, pocket galls or semicapsules, green or red, usually on upper surface on Salix alba, balsamifera [pyrifolia], discolor, and rostrata [bebbiana].
”- EP Felt: (1917) Key to American Insect Galls©
Reference: https://www.biodiversitylibrary.org/page/4885236#page/304/mode/1up