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: Speck Rot  

 


Speck rot (Phacidiopycnis washingtonensis) is a postharvest disease of apples. Fruit infection originates in the orchard. The source of the inoculum comes from dead or diseased plant tissue of the 'Manchurian' crabapple pollinizers in affected orchards. The fungus produces small black dots (fruiting bodies = pycnidia) on 'Manchurian' twigs, tree branches and crabapple fruit. Fruiting bodies contain millions of infective spores that can be spread by rain, irrigation or over-tree cooling to nearby apple trees and fruit. Although apple fruit infection occurs in the orchard, fruit rot symptoms develop during storage or at the market.
The cankers and twig dieback caused by P. washingtonensis are not common on apple trees in commercial apple orchards in Washington State, but the 'Manchurian' crabapple pollinizer trees are highly susceptible. Detailed pruning of this pollinizer is strongly recommended to significantly reduce the infective potential in commercial orchards.

Postharvest Fruit Syptoms Speck rot symptoms can occur as either stem-end rot (Fig. 1), as calyx-end rot (Fig. 2) or as both. The affected fruit tissue is spongy to firm, which is not differentiable from gray mold and not readily separable from the healthy tissue. The color of the decayed areas varies from light brown to dark brown or occassionally black. Speck rot is so named because of the brown to black specks with white to light tan centers that may appear around the lenticels, especially on red apple cultivars.

Additional Resources A newly produced factsheet about pruning 'Manchurian' crabapple pollinizer trees was released to the Pacific Northwest tree fruit industry. The factsheet can be downloaded here.

A separate factsheet guide specifically about speck rot can be downloaded here.

Sphearopsis rot symptoms

Figure 1: Stem-end rot symptoms on a Red Delicious apple after storage.

  Sphearopsis rot symptoms

Figure 2: Calyx-end rot symptoms on a Red Delicious apple after storage.

 

 

 

 

 

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