Apple Scab
Venturia inaequalis
Overview
One of the most serious diseases of apples and crabapples worldwide, causing olive-green to black velvety lesions on leaves and corky, scabby lesions on fruit.
Symptoms
Olive-green to dark brown velvety spots on leaves, often along veins. Spots darken and may cause leaf curling and premature drop. Fruit develops dark, corky, scab-like lesions that may crack. Severe infections cause misshapen fruit.
Environmental Conditions
Humid
Prevention
Plant scab-resistant varieties (Liberty, Enterprise, Freedom). Rake and destroy fallen leaves in autumn. Prune for good air circulation. Apply preventive fungicides from green tip through petal fall.
Management
Apply sulfur, copper, or lime-sulfur during primary infection period (spring). Continue applications through June in wet years. Remove severely infected fruit. Urea spray on fallen leaves in autumn accelerates decomposition.