These spots, the plant's reaction to enzymes injected into the leaf by the insect, can range from white to almost black depending on the host. Females cut slits into the host plant and lay six to eight eggs inside. There is one generation a year. It occurs during a six-week period from late May through June. 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 occurs per year, eggs are laid in the woody tissue and overwinter there. On problem trees, watch carefully for signs of activity in the spring. Examine terminal foliage for presence of the insects. Treat when leaves first open with Insecticidal Soap, Dursban, Malathion, Sevin, or Tempo.