What are these red scaly bumps on my willow bushes?

Asked September 21, 2015, 3:45 PM EDT

I just noticed some alarming hard, red, scaly bumps on my beautiful willow bushes. What are these? Are they harming my plant? Is there anything I can do?

Jefferson County Colorado trees and shrubs willows willow leaf galls

1 Response

The red/pink structures appear to be willow leaf galls, caused by an eriophyid mite. They will not harm the plant and no action is needed.
The galls are caused by eriophyid mite feeding or egg laying hormones, which stimulate the plant tissue to develop into these structures. The structure then serves as shelter, protection and food for the developing mites laid within.
Here's a great publication on the topic of eriophyid mites from Utah State University:https://extension.usu.edu/files/publications/factsheet/eriophyid-mites2010.pdf