Question: What are the growths on the leaves and twigs of my oaks? Can I control them?
Answer: Those are different types of galls, and they're caused by insects that sting the plant tissue and lay their eggs. Their larvae exist within the galls. You'll see many different types, from wooly and woody oak galls on live oaks to large tennis-ball-sized galls on red oaks. They are not especially harmful, nor is there any chemical control for them. Just ignore them.