Hello,

It is likely that the bumps on the maple leaves were caused by the maple bladder gall. The galls are caused by tiny sap-sucking mites. Galls are abnormal growths that occur on plants in response to irritation or stimulation of plant cells due to insects feeding or laying eggs. In this case, feeding by mites causes tiny bladder shaped green galls that change to red and then black. Often the galls drop out of the leaves, leaving tiny holes. Usually, the infestation by the mites ends by the end of July. Neither the mites nor the galls harm the tree. Read more here: https://entomology.ca.uky.edu/ef404

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