Disease

Apple scab

Venturia inaequalis (V. pyrina on pear)

A fungus that overwinters in fallen leaves and infects new leaves and fruit during spring rains. It weakens trees and spots fruit, and severe years defoliate them by midsummer.

Signs

• Olive-green to black, velvety spots on leaves, which yellow and drop.
• Dark, scabby, corky spots on fruit, which may crack.
• Worst after wet springs on susceptible varieties.

What favors it

Wet spring weather from green tip until petal fall, with fallen leaves from last year under the tree.

Prevention

• Plant scab-resistant varieties, such as Liberty, Freedom and Pristine.
• Rake, mow or mulch fallen leaves in fall to cut spring spores.
• Prune for an open canopy that dries fast.

Crops it shows up on

Apple, pear & stone fruit; Shade & ornamental trees.

Often confused with

Sources

• Apple scab of apples and crabapplesUniversity of Minnesota Extension
• Apple ScabMontana State University Extension
• Apple Scab DiseaseUniversity of Maryland Extension
• Apple ScabUtah State University Extension

Why →