Colletotrichum viniferum

Initial symptoms appear as small brown or black spots with a lighter center on young leaves and shoots. As the disease progresses, these spots enlarge, taking on a sunken appearance with a distinct dark margin.

On berries, infection manifests as circular lesions that expand rapidly, causing fruit rot. The affected tissues become soft and are often covered with pinkish or grayish masses of fungal spores.

On woody canes, deep cankers form, which can lead to tissue necrosis and disrupt the supply of nutrients to the upper parts of the shoot. Severely affected shoots are often deformed and dry out prematurely.

In humid conditions, visible spore masses appear on the affected areas, forming characteristic small pads. This is a critical indicator used to differentiate this infection from other leaf spot diseases.

Affected leaves turn yellow, curl, and drop prematurely, which significantly reduces the vine's photosynthetic capacity and weakens the entire plant.

The causative agent of this disease is the fungus Colletotrichum viniferum, which belongs to the group of imperfect fungi (Deuteromycetes). The pathogen forms specialized structures called acervuli that break through the plant epidermis to release conidia.

This fungus exhibits high aggressiveness and can infect various parts of the grapevine throughout the growing season. The pathogen's biological cycle is heavily dependent on the presence of free moisture, which is essential for conidia germination.

The fungus overwinters primarily as mycelium in infected plant debris, vine bark, or mummified berries left on the trellis or fallen on the ground. In spring, as temperatures rise, active sporulation begins.

Infection spreads through conidia, which are dispersed by wind, rain splashes, or insects to healthy plant tissues. The incubation period can be quite short under high humidity conditions.

Unlike some other species, Colletotrichum viniferum displays a narrow specialization on grapes, adapting to the biochemical characteristics of the host plant.

The primary factor promoting disease development is high relative humidity, typically exceeding 80-90%. Frequent rainfall, fog, and heavy dew create an ideal environment for spore germination and infection.

The optimal temperature range for the fungus is between +20°C and +28°C. Under these conditions, the pathogen's life cycle is significantly shortened, potentially leading to widespread outbreaks.

Crowded vineyard canopies and poor air circulation significantly increase the risk of infection. Insufficient ventilation within the vine canopy allows moisture to persist on leaf surfaces for longer periods.

Poor agricultural practices, such as delayed shoot thinning or improper canopy management, contribute to a stagnant microclimate that fosters pathogen activity.

Plants under stress due to nutrient deficiencies or pest damage are more susceptible to the penetration and colonization of this fungal pathogen.

The main economic danger lies in the damage to the berries, which renders the harvest unsuitable for processing or storage. The fungus can destroy a significant portion of the clusters before they reach maturity.

Damage to the canes prevents proper lignification, which reduces the vine's frost resistance during the winter. This increases the risk of cold damage or winter killing of the grapevines.

Premature loss of leaf area impairs sugar accumulation in berries and negatively impacts the vine's overall energy reserves, which are vital for fruit bud formation in the following season.

In nurseries or young plantations, severe infection can lead to the death of individual plants, resulting in significant losses for growers.

The cost of vineyard management increases due to the need for additional fungicidal treatments required to protect the crop throughout the season.

The most important preventive measure is the systematic removal and destruction of all infected parts of the vine and plant debris, which serve as reservoirs for the pathogen.

Ensuring proper air circulation by conducting timely canopy management, such as shoot thinning and leaf pulling, reduces humidity within the vine and minimizes infection risk.

Applying copper-based fungicides in early spring helps significantly reduce the primary inoculum load on the vineyard before active growth begins.

During the growing season, it is recommended to use systemic fungicides with broad-spectrum activity that offer both protective and curative effects against fungal pathogens.

• Utilize grape varieties with known genetic resistance.
• Maintain proper spacing when establishing new vineyards.
• Regular monitoring of leaves and clusters for early symptoms.
• Balanced nutrient application to enhance the plant's natural immune system.