WSU Extension


Anthracnose and Bull's-eye rot 
Bitter pit 
Crown and collar rot 
Crown gall 
Cytospora canker 
Fire blight 
Fruit russeting 
Nectria canker (European canker) 
Nectria twig blight (Coral spot) 
Perennial canker (Bull's-eye rot) 
Phytophthora fruit rot 
Powdery mildew 
Virus diseases 
Apple ermine moth 
Apple maggot 
Apple-and-thorn skeletonizer 
Brown marmorated stink bug 
Codling moth 
Cutworms and armyworms 
Fruittree leafroller 
Lecanium scale 
San Jose scale 
Spider mites 
Tent caterpillars 
Tentiform leafminer 

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Caption: Apple scab on fruit
Photo by: R.S. Byther
Apple : Scab
(revision date: 3/10/2017)

Apple scab is caused by a fungus which also causes scab on crabapple and hawthorn. The first infections occur during wet weather in the spring. Initially, the disease causes tiny, pale, chlorotic, water-soaked spots on the leaves. The spots enlarge and darken to a dark, velvety, olive-green then to black. Leaves may become distorted, puckered, and mottled. Leaves may drop, sometimes resulting in severe defoliation of susceptible trees. Scab can also affect fruit. Fruits infected early in development show olive-green to brown, roughened or corky spots which may develop deep cracks. These apples are often misshapen. Fruits infected at later stages develop small black "pinpoint" scab spots while in storage. The disease is favored by cool, wet conditions and overwinters in infected plant debris. Refer to PNW0582 Apple Scab for more information.
Management Options

Non-Chemical Management
  • Plant scab-resistant varieties such as 'Akane', 'Chehalis', 'Liberty', 'Paulared', 'Prima', or 'Tydeman Red'.
  • Plant in full sun.
  • Space plantings and prune to provide good air circulation and light penetration.
  • Avoid overhead irrigation.
  • Rake and destroy (do not compost) fallen leaves, or cover them with soil.
  • The application of nitrogen to the leaves in the fall will enhance the decomposition of the fallen leaves.
Select non-chemical management options as your first choice!

Chemical Management

Apply fungicides when leaves are separating, just exposing bud cluster. Repeat at 7-day intervals for 3 or more applications until weather dries. When in blossom, wait until 3/4 of petals have fallen before applying. Homeowners should not make foliar applications to trees over 10 ft tall. Consult a commercial pesticide applicator for treatment of trees and shrubs over 10 ft. tall.

Listed below are examples of pesticides that are legal in Washington. Always read and follow all label directions.
  • Bonide Fruit Tree & Plant Guard R-T-Spray
    Active ingredient: boscalid, lambda-cyhalothrin, pyraclostrobin  |  EPA reg no: 4-488
  • Captan 50% WP Fruit & Ornamental
    Active ingredient: captan  |  EPA reg no: 4-459
  • ferti-lome F-Stop Lawn & Garden Fungicide RTS
    Active ingredient: myclobutanil  |  EPA reg no: 7401-505
  • Spectracide IMMUNOX Multi-Purpose Fungicide Spray Conc
    Active ingredient: myclobutanil  |  EPA reg no: 9688-123-8845
  • This list may not include all products registered for this use.

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Caption: Apple scab on fruit
Photo by: R.S. Byther
Caption: Apple scab on leaf
Photo by: R.S. Byther
Caption: Apple scab
Photo by: R.S. Byther