Neoconiothyrium viticola

The first noticeable signs are brown or dark brown spots on the shoots, which eventually enlarge and become sunken. These areas of the bark may crack as the disease progresses deeper into the tissue.

Beneath the bark, the wood displays unhealthy brown or black discoloration. Removing the bark reveals necrotic lesions that can girdle the shoot, causing the portion above the lesion to wither and die.

Small black dots, known as pycnidia, often appear on the surface of the dead bark. These are the fungal fruiting bodies and are most prominent during periods of high humidity when the fungus is actively sporulating.

Young shoots affected by the disease show stunted growth and twisting. Eventually, the infected shoots die, and the foliage attached to them may turn yellow and drop prematurely.

It is important to distinguish this necrosis from other leaf spot diseases, as the impact of Neoconiothyrium viticola is primarily on the structural integrity of the vine, weakening the entire plant.

The causal agent of this disease is the micromycete Neoconiothyrium viticola, a fungus known to affect the woody parts of grapevines. It is a specialized parasite capable of surviving for long periods within infected tissues and plant debris.

The fungus belongs to the order Pleosporales and produces pycnidia, which serve as the primary source of inoculum during the spring. The pathogen has the ability to penetrate deep into the cambium layer, making it difficult to treat with superficial fungicides.

Unlike many foliar pathogens, this fungus is primarily xylotrophic, colonizing the woody skeleton of the vine. It is frequently found in disease complexes occurring after winter injury or improper pruning practices.

Spore dispersal occurs mainly through rain splashes and wind. Whenever open wounds are present on the vine, the fungus quickly colonizes the exposed tissues, initiating the process of cellular decay.

A key biological characteristic of Neoconiothyrium viticola is its long latent period, meaning that external symptoms often appear long after the initial infection has established itself deep inside the plant.

The active development of Neoconiothyrium viticola is directly linked to high humidity and moderate temperatures. Rainfall is the most critical environmental factor for moving spores across the vineyard.

Favorable conditions for infection include mechanical damage from pruning, hail, or cold stress during the dormant season, which creates entry points for the pathogen.

Poor agricultural practices, such as overly dense canopy management and lack of airflow, create microclimates with high humidity that facilitate rapid pathogen spread throughout the vineyard.

Vines that are already stressed due to nutrient deficiencies or frost damage are significantly more vulnerable to colonization by this pathogen compared to healthy, vigorous plants.

Prolonged foggy periods and heavy dew towards the end of the season can lead to secondary infections, building up a large pool of inoculum for the following growing season.

The primary danger of this disease lies in its hidden damage to the vascular system of the vine. Gradual necrosis of the xylem limits water and nutrient flow, leading to the overall decline of the grapevine.

The economic impact manifests as reduced yields, as infected shoots fail to support healthy cluster development. In severe cases, entire cordons or even the whole vine may die, necessitating replanting.

The disease significantly degrades wood quality, rendering the framework of the vine brittle and unsuitable for long-term production. This often requires radical rejuvenation pruning to restore the plant.

Infection by Neoconiothyrium viticola lowers the vine's overall immunity, making it more susceptible to secondary fungal or bacterial infections, leading to a synergistic decline of the plant.

Economic losses arise from the costs of intensive fungicide programs, harvest reductions, and the labor-intensive need to prune out or replace affected vines in the vineyard.

Protection begins with strict sanitation: removing and destroying all infected wood. All pruning cuts should be protected with fungicides or wound-healing pastes to prevent pathogen entry.

Good agricultural practices are essential, including proper canopy management and airflow to ensure the vines dry out quickly after rain. Consistent vine health through balanced nutrition is key to resistance.

• Early spring applications of copper-based fungicides.
• Use of systemic fungicides during high-risk infection periods.
• Regular sanitation to clear the vineyard of infected debris.
• Monitoring and maintenance of plant health to ensure resistance.

The protection strategy should be integrated. Using copper-based compounds and modern fungicides helps suppress the fungus, but these must be applied proactively rather than reactively.

If symptoms are detected, tools must be disinfected after each cut, particularly when removing infected parts, to avoid spreading the fungal spores to healthy tissue or other vines in the block.