Infected leaves have dead areas following the midrib or larger veins.
These light brown blotches may run together and, in severe cases, cause leaf drop. Trees of low vigor, repeatedly defoliated, may die. Trees defoliated several years in a row may need spraying. Apply the first spray at bud break and make additional sprays at 10 day intervals if average temperatures are below 55 degrees. Canker diseases can either attack the trunk or the branches.