Alternaria rot of grapes

Alternaria rot of grapes is a fungal disease caused by the pathogen Alternaria viticola. This fungus belongs to the genus Alternaria and is recognized as a significant threat to viticulture, capable of causing premature leaf drop and serious damage to grape clusters during the growing season.

The primary host for this pathogen is the grapevine. The fungus affects all green parts of the plant, but the most severe damage occurs on leaves and berries. In many cases, it acts as a secondary pathogen that colonizes tissues weakened by other physiological or mechanical stress factors.

Symptoms typically manifest as necrotic spots on the leaves, which eventually develop a characteristic olive-grey velvety fungal growth. On the berries, the infection causes the fruit to shrivel and become covered with dark, sooty mold, leading to fruit decay and rendering the harvest unsuitable for processing or fresh consumption.

Disease development is favored by warm, humid weather conditions, especially frequent rainfall or heavy dew. The fungus survives the winter as mycelium or spores within plant debris and bark cracks, allowing it to re-infect the vineyard early in the next season when environmental conditions become suitable for fungal growth.

Integrated pest management is essential to control the disease, which involves

• proper canopy management to enhance airflow and reduce humidity
• rigorous sanitation by removing and burning infected pruning residues
• monitoring for early signs of fungal activity during the summer
• applying protective and systemic fungicides during high-risk growth stages