Good Morning Mary, 

Thank you for contacting the U of M Extension Service. 

Please click on the following link from the U of M Extension Yard and Garden website: 

https://extension.umn.edu/yard-and-garden-insects/insect-and-mite-galls

Control is generally not suggested. Please read through the information. As you scroll down, you can expand the sections that discuss protecting your plants. 

The above information states: 

• Can be a problem when galls are numerous on very young plants.
• Damage may occur if there are many galls on branches or present for several years in a row.
• In most cases, galls are not numerous enough to harm the plant.

Good Luck!