Gnomoniopsis comari leaf spot

Pathogen and disease type. The pathogen Gnomoniopsis comari is a fungal agent responsible for leaf spot in strawberries. It belongs to the Ascomycota division and functions as a necrotrophic parasite, invading leaf tissues and causing localized cell death. The pathogen is highly persistent, capable of overwintering in plant debris, which ensures the continuity of the infection cycle from one growing season to the next.

Affected crops. The primary host for this fungus is the cultivated strawberry (Fragaria × ananassa). The disease is widely distributed in regions with temperate climates where strawberry production is concentrated. While it mainly targets strawberries, the fungus can also impact other members of the Rosaceae family, making them potential reservoirs for inoculum during the off-season.

Symptoms and signs. The clinical manifestation of the disease begins with the appearance of small, circular, reddish-brown spots on the leaf surface. As the infection progresses, the spots expand, and the center often fades to a pale grayish-brown, frequently surrounded by a dark purple or maroon border. Under magnification, one can see tiny black pycnidia scattered across the necrotic tissue, which serve as the primary site for spore dispersal.

Conditions for development. The fungus thrives in cool to moderate temperatures and high humidity levels. Prolonged periods of rainfall, heavy dew, and high canopy density facilitate the germination of spores and their spread via water splash. The disease tends to be more severe in poorly managed plots where air circulation is restricted and old, infected foliage is allowed to remain on the soil surface.

Prevention and control measures. Integrated pest management (IPM) is essential for controlling Gnomoniopsis comari. Cultural practices include the removal of infected leaves and crop debris to reduce the initial inoculum level. Adequate spacing between plants and the use of raised beds can improve air circulation and reduce humidity around the foliage.

• Application of appropriate fungicides during the early stages of infection.
• Ensuring the use of disease-free propagation material.
• Proper pruning to enhance airflow.
• Monitoring soil moisture to avoid prolonged leaf wetness.