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Cherry leafspot
Blumeriella jaapii (= Coccomyces hiemalis)
Synonyms
 
None
 

Plant hosts

  • Major hosts: Prunus avium (sweet cherry), Prunus cerasus (sour cherry)
  • Minor hosts: Prunus americana (apricot), Prunus armeniaca (apricot), Prunus cerasifera (myrobalan plum), Prunus domestica (plum), Prunus fruticosa (dwarf cherry), Prunus mahaleb (mahaleb cherry), Prunus padus (bird cherry), Prunus pennsylvanica, Prunus serotina (black cherry), Prunus serrulata (Japanese flowering cherry), Prunus virginiana (common chokecherry tree)

 
 

Symptoms
 
On sour cherry leaves, variously colored spots develop on the upper surface. The spots or lesion rapidly enlarges, becoming brown or purple, and dies from the center outward. Infected spots are irregular or round and occur over the entire leaf surface. Individual spots never become large. They merge together to kill large areas of the leaf. Spot development precedes yellowing and leaf dropping. The area adjacent to the spot may remain green while the rest of the leaf turns yellow. Diseased leaf tissue may separate from healthy tissue and give the leaf a shothole appearance.
 
On sweet cherry leaves, spots often are larger and nearly circular. Cream-colored fungal spore masses appear on the lower leaf surface associated with the spots on both sweet and sour cherries. On fruit stems, infections sometimes girdle the stem to cause a fruit drop. While infections occur on the fruit, they are less common than on foliage.
 
Symptoms of cherry leaf spot
 
Symptomatic leaves turning yellow
 
Photo courtesy of Haywood Photography 2005 from An Online Guide to Plant Disease Control, Oregon Sate University Extension
 
 
 

Transmission
 
The fungus overwinters on dead cherry leaves on the ground. In early spring, fungal fruiting bodies called apothecia develop in these leaves. Spores that develop in the apothecia are dispersed by air currents and rain splash to emerging new leaves in the canopy above. Spores germinate when moisture is present and enter leaves through stomates (natural openings). As lesions develop, more spores can be produced and dispersed. The disease can have many life cycles in a single growing season. Disease is particularly severe in sour cherry, but also occurs on sweet cherries in western Washington and Oregon. The pathogen is not known to be seedborne.
 

Geographic distribution
 
Cherry leaf spot is distributed in North America, Europe, and Asia.

Applicable regulations
 
Cherry leafspot is a pathogen of concern to Oregon's interstate and international customers. Survey and diagnosis is available through the Commodity Inspection Division for this fungus.
 
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