Chrysanthemum cercospora leaf spot

The disease is caused by the fungus Chuppomyces handelii, historically known as a Cercospora species. It is a significant foliar pathogen that affects the aesthetic value and overall physiological health of ornamental plants by disrupting their photosynthetic capacity.

The primary host for this pathogen is the Chrysanthemum genus. The fungus is particularly damaging to commercial greenhouse crops, where high plant density and controlled environmental conditions often favor rapid disease colonization and spread throughout the population.

Symptoms typically manifest as small, circular or irregular spots on the foliage. These spots eventually turn tan or brown with darker margins. As the infection progresses, the tissues surrounding the lesions may become chlorotic, leading to early leaf yellowing, browning, and premature senescence of the foliage.

Environmental conditions such as high humidity, excessive dew, and moderate temperatures are ideal for the development of Chuppomyces handelii. Conidia, the asexual spores of the fungus, are disseminated by splashing water, wind, and movement of infected plant material, ensuring the survival of the pathogen in plant debris over the winter.

Managing this disease requires a focus on sanitation and environmental control to break the infection cycle. Practical steps include the following:

• Remove and destroy all infected plant material to reduce inoculum levels.
• Promote good air circulation to reduce humidity around the foliage.
• Implement drip irrigation to avoid wetting the leaves.
• Apply preventative fungicide treatments during periods of high disease pressure.