Hi Donna, Most pin oaks will have at least some galls on them and some pin oaks have a lot of galls without much impact to them. Usually if a pin oak has TONS of galls on it, it is because something else is stressing the tree enough for it to reduce its ability to defend against the galls. Topping a tree is never a good idea. The large wounds created by topping will be points where rot can form and other pathogens can enter the tree. In addition, when you top a tree, the branches that form afterwards generally have bad connections because there are clusters of small tiny branches all sprouting from the same point. This leads to more stem failures and rot in the future of the tree and can drastically shorten the life of a tree and make it much more likely to have limb failures. Topping a tree is very stressful for the tree and will only make it more susceptible to future gall wasps. Can you prune out any dead wood in the tree and reduce the living canopy somewhat through proper pruning but you would not want to remove more than around 25-30% of the living canopy of the tree in any one growing season. Overall, I would start by trying to determine if your pin oak is suffering from any other stresses. Often pin oaks have nutrient deficiencies, especially iron, brought on by soil pH that is too high or is drought susceptible, especially when planted in a dry sight (pin oaks are naturally a wetland species so do best with adequate soil moisture).
