Pseudopestalotiopsis leaf spot

Causal agent and disease type. The fungus Pseudopestalotiopsis theae is the primary causative agent of this disease, belonging to the Ascomycota phylum. It is classified as a necrotrophic pathogen that causes severe leaf spots and twig blights. The fungus survives as mycelium or conidia in infected plant debris, serving as the main reservoir for recurring infections each growing season.

Susceptible crops. The disease primarily affects tea plants (Camellia sinensis). It is a significant concern for commercial tea cultivation, as the pathogen impairs the quality and quantity of the harvest. While it is most prevalent in tea, it can also manifest in other related species within the Theaceae family under favorable environmental conditions.

Symptoms and signs. The infection typically manifests as brown to necrotic gray spots on the leaf blades. These lesions often have distinct darker margins and, over time, develop small black dots called acervuli, which contain the fungal spores. Severe infections lead to premature leaf abscission, tip dieback of young shoots, and reduced plant vigor, significantly impacting the tea crop's cosmetic and chemical quality.

Conditions for development and spread. The disease thrives in high-humidity environments, especially during periods of frequent rainfall and moderate temperatures. Inadequate spacing between tea bushes and poor canopy ventilation create a humid microclimate that favors spore germination and mycelial growth. Spores are primarily dispersed by splashing water, rain, wind, and agricultural machinery used in daily maintenance.

Damage and control measures. Economic damage is caused by the reduction of healthy leaf area, leading to lower yields and inferior tea grade. Effective disease management includes the removal and destruction of infected plant material to reduce inoculum levels. Cultural practices like pruning to improve airflow and selecting disease-resistant cultivars are essential. Fungicide applications, particularly those containing copper or systemic active ingredients, are used during high-risk periods, adhering to strict safety protocols for harvesting.