Cercospora leaf spots are a common issue affecting many ornamental crops like hostas, hydrangea, hibiscus, pansy, verbena, gardenia, and others. However, starting in the Fall of 2022, an increase in damage caused by the pathogen in Spathiyphyllum plants appeared. Spots are first noticeable on older leaves at the bottom of the plant and then spread upward.
The spots are brown, irregular in shape, and can grow up to 1 centimeter in size.
To manage cercospora leaf spot, it’s important to practice good sanitation by removing infected leaves. Overhead watering should be avoided. Drip irrigation, good ventilation and increased plant spacing can help lower humidity and temperature, making it easier to manage the disease.
Fungicides containing chlorothalonil, thiophanate-methyl, and FRAC group 3 (e.g., Banner Maxx II, Trinity, Eagle) are effective in controlling cercospora leaf spot when applied before or at the first sign of symptoms. Combo premix products containing FRAC 7 & 11 (Broadform, Orkestra Intrinsic, Mural) have also been effective in managing the disease. Multiple application rotations (every 10-14 days) may be necessary to keep plants free of the disease.
By David Norman, Ph. D., Plant Pathologist, UF IFAS MREC
Liz Felter, Ph.D., Production Horticulture Extension Agent, UF IFAS MREC
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