Pseudocercospora leaf spot of pittosporum

Pathogen and disease type: The disease is caused by the fungal pathogen Pseudocercospora pittospori. It manifests as a leaf spot disease, characterized by the colonisation of host leaves, leading to tissue necrosis and significant impairment of the plant's photosynthetic ability.

Susceptible hosts: The primary host for this fungus is the genus Pittosporum. It is commonly found in nursery environments, landscape plantings, and conservatories where plants are grown in close proximity, facilitating the rapid spread of the pathogen.

Symptoms and signs: Early symptoms present as small chlorotic spots on the leaves. As the infection progresses, these spots expand and turn brown, dark red, or nearly black, often surrounded by a chlorotic halo. In severe cases, the foliage becomes necrotic, leading to leaf drop and a significant decline in the plant's ornamental appeal.

Development and spread: The fungus thrives in warm, humid environments where foliage remains wet for extended periods. Humidity levels and lack of proper air circulation are critical factors that promote spore germination and subsequent infection. Spores are dispersed through splashing water during irrigation or rain, as well as through air currents.

Damage and management: The economic impact is mainly felt in the nursery industry due to the devaluation of infected nursery stock. Control measures include strictly avoiding overhead irrigation, ensuring adequate spacing for proper airflow, and prompt removal of infected plant debris. Chemical control using copper-based fungicides or systemic products can be effective if applied during the early stages of the disease.