I found these "galls" on my oak bonsai on April 10th. I'd like to know if I need to worry about them coming back. You can see the end of the branch they were on was dead. It's a little bonsai and can't afford to lose any more branches. These galls are about the size of a bb.
Washington County Oregon galls
Thank you for your question. These are galls, and are caused by a wasp. Many galls are harmless, and I don’t know what type you have. Here is an Extension article on them: https://extension.oregonstate.edu/forests/tree-care/galls Here’s another article with limited control options: http://ipm.ucanr.edu/PMG/GARDEN/PLANTS/INVERT/gallmakers.html Good luck!