Stenella citri-grisea

Stenella citri-grisea is a specialized fungal pathogen belonging to the kingdom Fungi, phylum Ascomycota, and genus Stenella. It acts as a phytopathogen specifically targeting citrus species, causing significant leaf spot disease. The fungus thrives as a parasite, obtaining nutrients from host plant cells and causing necrotic lesions.

The disease manifests as gray to grayish-brown spots on the leaf blades of citrus trees. As the infection progresses, the spots enlarge, and fungal sporulation occurs, often appearing as a velvety growth on the lesion surface. This tissue damage significantly impacts the plant's photosynthetic efficiency, leading to leaf yellowing, early defoliation, and overall tree weakening.

The life cycle of the pathogen is driven by environmental conditions. The fungus overwinters primarily in infected leaf litter and debris as mycelia or conidia. When favorable conditions return, conidia are dispersed by wind and rain splashes to new, susceptible leaves. Infection occurs when the fungus penetrates the plant tissue through stomata or mechanical wounds.

Development and spread are heavily influenced by humidity and temperature. Optimal conditions for disease progression are high relative humidity and moderate temperatures ranging from 20°C to 25°C. Prolonged wet periods significantly enhance the infection rate, making dense canopy management crucial for mitigating the impact of the disease in commercial orchards.

To effectively manage and control this pathogen, growers should implement an integrated approach:

• Maintain strict sanitation by removing and destroying fallen infected leaves.
• Prune citrus canopies to promote better airflow and reduce micro-humidity levels.
• Apply preventive copper-based or systemic fungicides during vulnerable growth stages.
• Monitor plantations regularly for early signs of gray leaf spot development.