Colletotrichum viniferum

Pathogen and disease type. The disease is caused by the pathogenic fungus Colletotrichum viniferum, which is classified as an Ascomycete. It acts as the primary causative agent of anthracnose in grapevines. The fungus survives as mycelium within infected host tissues or crop residues throughout the winter season, preparing to infect the new growth of the grapevine as soon as conditions become favorable.

Host range. The pathogen primarily targets cultivated grapevine species (Vitis vinifera). While it is highly specialized, its severity depends on the specific cultivar's susceptibility to the fungus. Vineyard environments with poor airflow and high humidity create a conducive setting for the pathogen to establish itself and proliferate across diverse grape varieties.

Symptoms and signs. Initial signs include the appearance of small, brown or grey necrotic spots on leaves, shoots, and petioles, often surrounded by a dark, distinct halo. As the infection progresses, these spots expand into deep, sunken lesions or cankers. Berries are also highly susceptible, showing depressed, dark lesions that eventually lead to fruit decay and mummification, rendering the crop unmarketable.

Development and impact. The development of Colletotrichum viniferum is driven by high humidity, prolonged leaf wetness, and moderate temperatures, which facilitate spore germination and fungal colonization. The impact on viticulture is significant, as it causes massive defoliation, stunted growth, weakened cane development, and substantial yield losses. In severe outbreaks, the entire crop can be compromised.

Protection and prevention. Effective management requires an integrated approach to reduce fungal pressure and prevent the spread of the disease:

• Strict sanitation, including the removal and destruction of infected canes and leaves.
• Maintaining optimal vine canopy density to ensure good ventilation and rapid drying of foliage.
• Applying copper-based fungicides or appropriate systemic treatments during the growing season.
• Conducting preventative spray programs early in the season to manage initial inoculum.
• Selecting resistant or tolerant grape cultivars to mitigate long-term disease risks.