Stemphylium rot

Stemphylium rot is a severe fungal disease caused by the ascomycete Stemphylium vesicarium. This pathogen belongs to the leaf spot disease group and affects a wide range of crops, including onions, garlic, tomatoes, asparagus, pears, and tropical plants such as Indian mango.

Symptoms typically appear as small, light-colored lesions that rapidly expand and turn brown or dark gray. Frequently, a yellowish halo forms around the infected areas. Under conditions of high humidity, an olive-black fungal growth consisting of conidia develops on the spots, leading to premature leaf drying and tissue necrosis.

The pathogen thrives during periods of moderately warm weather combined with high air humidity, frequent rainfall, or heavy dew. The fungus overwinters in the soil and on crop debris, from where its conidia are dispersed by wind and rain splashes. Optimal conditions for infection occur at temperatures between +18 and +25 degrees Celsius when surface moisture is present on the leaves.

The economic impact of the disease is significant, as it reduces the photosynthetic surface area, weakens the plant, and leads to substantial yield losses. In Indian mango, the infection damages fruits and inflorescences, rendering produce unmarketable and degrading its quality. Without proper management, the disease can cause devastating losses in both fields and orchards.

Protection strategies involve an integrated approach: selecting resistant varieties, maintaining crop rotation, and thoroughly removing infected plant debris. Prophylactic application of fungicides, such as copper-based products or systemic treatments from the strobilurin and triazole classes, is highly effective. It is also crucial to manage greenhouse humidity and ensure adequate ventilation to prevent the spread of the infection.