Pecan Scab Severe scab infections on nuts. With warmer temperatures and rainfall in the spring, fungal spores are produced on the stroma. Dew and rain spread spores locally within a tree, and the wind spreads them over long distances to adjacent trees or orchards. All tissues are most susceptible when young and actively growing. Lesions expand and may coalesce.
Old lesions crack and fall out of the leaf blade, giving a shot-hole appearance.
Nut infections cause the greatest economic damage. Early infections may cause premature nut drop but more commonly cause the shuck to adhere to the nut surface, causing sticktights. Late infections can prevent nuts from fully expanding and decrease nut size. Control Resistant varieties offer the first line of defense against pecan scab because pecan varieties vary greatly in their susceptibility to pecan scab. Some varieties are resistant, but many grafted varieties are susceptible.