Botrytis leaf blight

Botrytis leaf blight, also known as flower and capsule blight, is a destructive fungal disease caused by the pathogen Botrytis squamosa. It is a major concern for growers, as it can cause significant yield losses by damaging the photosynthetic foliage and the reproductive organs of the plants.

The primary hosts for this pathogen are onions and garlic. In seed crops, the infection is particularly devastating, as it targets flower stalks and seed capsules, frequently causing them to collapse prematurely and severely reducing seed viability and overall harvest yield.

Symptoms typically begin as small white, necrotic spots on the leaves, surrounded by a pale green halo. As the disease progresses, especially in wet conditions, these spots expand into large lesions. Under high humidity, a characteristic gray, fuzzy mycelial growth develops on the infected tissues.

The development and spread of the fungus are strongly favored by cool, moist weather and prolonged periods of leaf wetness. Botrytis squamosa survives the off-season as sclerotia in the soil or in crop debris, which acts as a primary inoculum source when environmental conditions become favorable.

Effective management requires an integrated approach. Essential practices include practicing crop rotation, ensuring proper field sanitation by burying or removing infected plant debris, and maintaining adequate spacing to improve airflow. Fungicide applications are necessary during periods of high disease pressure to prevent the pathogen from establishing on healthy foliage.