MAPLE TREE PROBLEM
This is what we all a Bladder Gall. It is caused by an Eriophyid mite which is host specific (these galls will only appear like this on Maple and not other plants). Once the injury is evident it is too late for treatment. The galls shouldn't be injurious to the tree other than the unsightliness of their appearance. If the client wishes they may treat with a miticide in the spring just as the leaves are unfurling. Avid or Talstar may be effective miticides for them to try.
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