Zantedeschia cercospora leaf spot

The causal agent of this fungal disease is Cercospora richardiicola, a pathogen that specifically targets plants within the Araceae family. This fungus is a significant concern for growers of ornamental plants, particularly in indoor and protected cultivation environments where it can cause considerable damage to foliage.

The primary host for Cercospora richardiicola is the Zantedeschia (commonly known as Calla lily). While other aroids may occasionally be affected, the disease is most frequently and severely observed on Zantedeschia crops grown for flower production or ornamental sales in greenhouses and botanical garden collections.

Symptoms of the infection manifest as discrete spots on the leaves. Initially, these spots appear as small yellow or light green lesions that eventually develop into brown or grey necrotic areas with a distinct darker margin. Under conditions of high humidity, sporulation of the fungus occurs, visible as a greyish velvety coating on the necrotic tissue.

The development of the fungus is highly dependent on environmental conditions. It thrives in warm, humid climates with poor air circulation. Spores are primarily disseminated by water splashes during irrigation, wind currents, and through the handling of contaminated gardening tools. High planting density significantly accelerates the rate of spread within a greenhouse.

Effective management requires an integrated approach to plant health. Key measures include removing and destroying infected plant tissue promptly to reduce inoculum levels. Improving greenhouse ventilation to lower relative humidity and employing bottom-watering techniques can prevent leaf wetness. If chemical intervention is necessary, fungicides containing copper compounds or triazoles are often used to suppress fungal growth and protect healthy foliage.