Tree Fruit Research & Extension Center

Cullage Assessment & Education

Quick Identification Guide to Apple Postharvest Defects & Disorders

Postharvest Diseases

The Diseases section of the card set includes all the major fungal diseases found in stored Washington apples. This section also includes a Symptom Comparison Table to help. At a later date more cards may be developed for this section which would include any newly discovered pathogens. For ordering information visit the Order Information section of the Introduction. The cards shown on this site are slightly modified to accomodate web formatting. Figures may appear fragmented in some browsers. Please report viewing problems here. Any reproduction of the card images or content without permission is in violation of WSU Copyright policies.

Postscript:  Since the publication of this card set, a new fungal disease was discovered and identified, Phacidiopycnis washingtonensis, AKA Speck rot. This fungas has become a serious quarantine pest for some export markets, such as China. Dr. YK Kim and Dr. CL Xiao, both formerly of WSU, fully describe this disease in their paper found here. Although not found in the printed card set, we have included a description of this disease with the other fungal disease below.



DISEASES: Mucor Rot & Powdery Mildew  

  Mucor rot   Powdery mildew russetting

Mucor rot can cause significant losses of fruit, but is generally not a major problem when good harvest management and water sanitation practices at packing are implemented.

Figure 1: Mucor rot (Mucor piriformis) on a Golden Delicious fruit showing very soft, juicy, decayed tissue with a sharp margin. Mucor rot decay often has a sweet odor.


Powdery mildew may be found on apple buds, blossoms, leaves, twigs and fruit. When fruit are infected, the surface may become russetted or discolored, and sometimes dwarfed. Fruit is most susceptible during the period around petal fall.

Figure 2: Powdery mildew may result in a net-like scarring called russetting.




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