Repeated defoliation from severe downy spot infection can cause losses in nut production and tree vigor. Downy spot first appears on the lower surface of young foliage in late spring as small yellow spots. These spots may turn white as spores are produced. Later in the season, the lesions turn brown and begin to appear on the upper surface of the leaf. Heavily infected leaves drop earlier than healthy ones in the fall.
Downy spot survives the winter in fallen leaves.
Spores are released prior to budbreak. Downy spot begins in the lower parts of the tree and spreads upward. Unfortunately, Schley and Western are highly susceptible to pecan scab and Success and Western are susceptible to shuck dieback. Remove and destroy fallen leaves. Brown spot is found primarily in neglected orchards in areas that have abundant rainfall or high humidity.