Grapevine cercospora leaf spot

Systematic position and nature of the pathogen. Pseudocercospora vitis (formerly classified under the genus Cercospora) is a fungal plant pathogen belonging to the phylum Ascomycota. It is a specialized necrotrophic fungus that primarily colonizes the leaf tissues of plants within the Vitaceae family, significantly impacting vine health.

Diseases and host plants. This pathogen is responsible for Cercospora leaf spot in grapevines. While the disease primarily targets the foliage, it can occasionally affect petioles and, in severe cases, the berries. The symptoms appear as dark, irregular or angular spots that eventually lead to leaf necrosis and senescence.

Biology and life cycle. The pathogen overwinters as mycelium and conidia within fallen leaf litter or on infected vine canes. As temperatures rise during the spring and early summer, conidia are produced and disseminated by wind, splashing rain, or irrigation water. Once they land on healthy leaves, the conidia germinate, penetrate the plant tissue via stomata, and colonize the intercellular spaces.

Conditions for development and spread. Development of Pseudocercospora vitis is strongly favored by high relative humidity (above 75%) and temperatures in the range of 20°C to 28°C. Dense vine canopies with restricted airflow create a microclimate that remains humid for extended periods, facilitating the infection process and the rapid spread of secondary inocula throughout the vineyard.

Economic impact and control strategies. The primary impact of the disease is premature defoliation, which reduces the plant's photosynthetic capacity, impairs wood maturation, and negatively affects both current fruit quality and vine winter hardiness. Management strategies include:

• Sanitation: Removing and destroying diseased plant debris to reduce the overwintering inoculum.
• Canopy management: Pruning and leaf thinning to improve aeration and drying.
• Chemical control: Applying copper-based fungicides or appropriate systemic fungicides during high-risk periods to prevent infection.