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. Producers should keep in mind that most commercial varieties were at one time resistant to pecan scab and have now become susceptible because of genetic changes in fungus virulence. Some trees are resistant, but some are moderately susceptible. Hirschi' is highly susceptible to pecan scab and will be defoliated and suffer severe nut loss without protective fungicide sprays.