Find information from UF/IFAS on recognizing and managing brown rot and greasy spot.

UF/IFAS researchers presented in late August on the symptoms and management of brown rot and greasy spot, two fungal diseases affecting Florida citrus. According to a Citrus Industry article, Multi-county citrus Extension agent, Mongi Zekri, shared information on recognizing the diseases’ symptoms while plant pathologist and associate professor, Megan Dewdney, shared information on managing the diseases. See the highlights below.

Recognizing and Managing Brown Rot and Greasy Spot

Brown Rot

Symptoms:

  • “usually most severe on early-maturing sweet-orange cultivars…”
  • “commonly appears from mid-August through October on mature or nearly mature fruit following extended periods of high rainfall.”
  • “Lesions on rinds are brown or tan and firm or leathery”
  • “At high humidity, brown rot-infected fruit become covered with white mycelia.”
  • “infected fruit usually drop and have an unpleasant odor.”

Management:

  • “includes raising tree skirts to increase air movement and promote drying of foliage, and to lower the risk of organism movement into the canopy.”
  • “only a single spray is often needed in late July prior to disease symptoms. Recommended plant defense-stimulating products are Aliette, Phostrol and ProPhyt, which provide 60 to 90 days of control.”
  • “Growers using copper can apply it before or after symptoms are visible”… it “is primarily protective against brown rot but can kill the inoculum and provide 45 to 60 days of control.”
  • “An October copper spray is needed in very rainy conditions.”
  • “Revus or Orondis Gold are good choices for late-season application if growers missed the earlier application window. They provide at least 30 days of protection.”

Greasy Spot

Symptoms:

  • “lesions appear yellow or dark brown to black on the underside of mature citrus leaves.”
  • “Affected leaves fall prematurely from the tree during the fall and winter, resulting in reduced tree vigor and yield.”

Management:

  • “full spray coverage of the underside of leaves is necessary for best control.”
  • “Full coverage can be achieved with higher spray volumes and slower tractor speeds.”
  • “Enable is a good fungicide substitute for copper if growers are concerned with stippling. Other fungicides effective against greasy spot are Double Nickel and Miravis Top.

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