WSU Extension

Hortsense

Caption: Strawberry common leaf spot
Photo by: R.S. Byther
  
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Strawberry : Common leaf spot
(revision date: 5/19/2015)


Biology
Common leaf spot is caused by a fungus that overwinters on old infected leaves. It produces abundant spores in lesions of infected leaves, and rain splashes them onto healthy tissue. Only young leaf tissue is susceptible to infecting, and long wet periods and warm temperatures encourage spread of the disease. Foliage symptoms start as dark purplish red spots, and eventually become grayish white. Developed spots are about a 1/10 inch in diameter, with a white center and reddish outline, and become scattered all over the leaf surface. Sometimes the whitish centers of spots fall out, leaving a hole in the leaf. Infections occur in moist weather and are most severe in spring and fall. "Olympus" and "Shuksan" cultivars are the most susceptible.
Management Options

Non-Chemical Management
  • Removing foliage after harvest reduces spore counts.
  • After harvest, renovate by removing leaves of June-bearing plants 0.5 inch above the crown, but do not mow other types.
Select non-chemical management options as your first choice!

Chemical Management


Leaf spot can still be a problem after renovation unless reinforced with chemical protection. Begin applying copper products when leaves emerge and continue weekly (every 10 to 14 days if using Bonide Copper Spray or Dust RTU) through the season.

Listed below are examples of pesticides that are legal in Washington. Always read and follow all label directions.
  • Bonide Copper Fungicide Spray or Dust RTU [Organic]
    Active ingredient: basic copper sulfate  |  EPA reg no: 4-58
  • Bonide Liquid Copper Fungicide Conc/Organic Gardening
    Active ingredient: copper octanoate  |  EPA reg no: 67702-2-4
  • Soap-Shield Flowable Liquid Copper Fungicide [Organic]
    Active ingredient: copper octanoate  |  EPA reg no: 67702-2-56872
  • This list may not include all products registered for this use.
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Caption: Strawberry common leaf spot
Photo by: R.S. Byther