Damage to the fruit usually shows up in late summer, when the August flight of the bivoltine strain is active. Bearing orchards are more likely to show some early corn borer damage on the fruit if growers relax their spray program in June or early July. Weedy sites provide plenty of alternative hosts for this insect, especially those containing broadleaf dock, ragweed, pigweed, smartweed, and barnyard grass. Penncap-M, Lannate, and Lorsban can give very good control of ECB larvae, provided application is made before the caterpillars become concealed in the plant tissue. White Apple Leafhopper WALH overwinters as an egg beneath the bark surface of wood that is 1-5 years old.
Overwintered eggs hatch from late pink to petal fall.
Nymphs feed on older cluster leaves from pink to petal fall. Both nymphs and adults remove chlorophyll from the leaves, causing a white mottling. Normally it is not necessary to sample for the first generation of WALH in western New York or the Champlain Valley because damage is not severe and populations are usually relatively low. If petal fall sampling is necessary in certain locations, such as the Hudson Valley, the suggested economic threshold is an average of 1 nymph per leaf on 10 fruit cluster leaves from each of 5 to 10 trees. New York field reports welcomed.