Premature leaf drop is possible later in the season when the second generation has further stippled the same leaves. Control is seldom warranted except on stressed or newly transplanted trees. Galls easily noticed now include spindle gall and bladder gall on several varieties of trees, and succulent oak gall on pin oak leaves. Once a gall has formed on a tree leaf, there is no way to control the gall. These insects do their damage early in the spring but the symptoms persist through the season.
Severe infestation can even cause twig dieback.
Adults occur from late May to early July. There is one generation per year. The eggs are laid in the woody tissue where they overwinter. On problem trees, watch carefully for signs of activity in the spring. Examine terminal foliage for presence of the insects.