Plant Disease Update for Commercial Plant Producers

Last Updated on February 21, 2023 by Chris Weber

Symptoms from the top side of the leaves.

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.

Symptoms as seen from the underside of the leaf.

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


Posted: February 21, 2023

Category: Pests & Disease, Pests & Disease, UF/IFAS Extension, UF/IFAS Research
Tags: Cercospora Leaf Spots, Gardenia, Hibiscus, Hostas, Hydrangea, Ornamental, Ornamentals, Pansy, Pest, Pest And Disease, Plant Disease, Spathiyphyllum, Verbena

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