Primetime Pruning and Tree Removals

“Galls” are a plant's reaction to infiltration by another organism. They are formed by the tree in order to insulate and sequester the infiltrator.
This inadvertently helps the insect (often an insect) complete it's life cycle and is usually of little notable harm to the plant.

This relationship is therefore often deemed to be "commensalism," which, unlike parasitism or mutualism, benefits one of the organisms, and leaves the other relatively unaffected.