Leaf galls on Live Oaks are becoming a minor problem this summer causing some leaf drop. The galls are caused by a hornet that lays it’s eggs on the leaf and stings the leaf. The sting or injection causes the tree leaf to mutate and create the gall around the eggs which protects them.
The gall doesn’t hurt the tree usually but if a leaf gets multiple galls it can interfere with the leafs ability to make chlorophyll. If the leaf can no longer help the tree and becomes a liability the tree will drop the leaf and grow a new one.
There is really nothing you can do to prevent leaf galls. They don’t usually cause any actual damage to Live Oaks so it’s best to just ignore them and don’t let it bother you.