Blackberry – Stem Gall
Q: I found this on my blackberry plant and thought you might know what it is. Should I remove it?
A: I think it is a stem gall caused by the egg laying accomplished by a midge insect. Galls typically do not hurt host plants, they simply serve as a protected place for immature insects to develop.
You can leave it in place or remove it and cut it open to see what’s inside.