Cercospora usually presents itself on the underside of a plant’s leaves as yellow spots. Over time, these yellow spots grow and will eventually take over the underside of the leaf if untreated.
By the time most growers notice Cercospora, it has spread to the topside of the leaves turning from a yellow to yellow-ish green color. As the fungus progresses, the color will change to purple-ish or even black. If left untreated, the entire infected leaf will die off and drop. Cercospora most often infects Dendrobiums but can be seen in other orchid varieties as well.
Using sterile clippers, remove infected leaves and dispose of them away from your plants. Spray infected plants with Captan Fungicide, Thiophanate Methyl or Mancozeb according to the manufacturer’s instruction. Be sure when spraying that the fungicide reaches into the leaf crevices to kill fungal spores.
Cercospera thrives in a wet environment. Place your plants so that the leaves receive air circulation and adequate sunlight to dry between waterings.
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Cercospora On Cattleya
Cercospora On Vanda