Pleospora leaf spot of gerbera

Pleospora leaf spot of gerbera is a fungal disease caused by the ascomycete Pleospora gerberae. This pathogen is a specific parasite that affects plants of the Asteraceae family, most notably the popular ornamental flower Gerbera jamesonii. The infection disrupts the plant's physiological processes, leading to reduced growth and poor floral quality.

The host range is primarily limited to gerbera cultivars grown in greenhouses and outdoor nurseries. The fungus primarily targets the leaves but can also impact stems if the environment is conducive to disease development. Because gerberas are grown for their decorative value, even minor infections significantly impact their commercial marketability.

Symptoms typically start as small, circular, or irregular brown to dark grey spots on the foliage. As the disease progresses, these spots enlarge and may merge, eventually leading to leaf chlorosis and necrosis. Under humid conditions, the pathogen produces small, dark fruiting bodies (pseudothecia) within the lesions, which serve as the source of secondary inoculum.

The disease development is heavily influenced by environmental factors such as high relative humidity, poor air circulation, and temperature fluctuations within the 18–25°C range. The fungus overwinters in plant debris and soil, easily spreading via water splashes during irrigation, air currents, or contaminated agricultural tools used during pruning or harvesting.

Effective management and prevention strategies include:

• Ensuring the use of certified disease-free planting material.
• Rigorous sanitation, including the removal and destruction of all infected plant parts.
• Implementing proper greenhouse climate control to keep foliage dry.
• Application of appropriate fungicides when weather conditions favor disease spread.
• Maintaining proper plant spacing to improve ventilation and reduce local humidity.