White rot of grapes

Pilidiella diplodiella is a fungal pathogen responsible for the disease known as white rot in grapevines. Taxonomically, it belongs to the Kingdom Fungi, Division Ascomycota, Order Diaporthales, and Family Schizoparmeaceae. This pathogen is a specialized parasite that exclusively targets Vitis species.

The symptoms of white rot are characterized by the rapid browning and shrinking of grape berries. As the disease progresses, numerous small, light-colored fruiting bodies called pycnidia appear on the surface of the berries. Under humid conditions, these pycnidia release spores that facilitate the secondary spread of the infection to nearby clusters.

The biology of the fungus is centered on its ability to survive the winter in infected plant debris or in the soil. During the growing season, particularly after periods of high humidity and rainfall, the fungus produces pycnidia. Infection typically occurs when raindrops splash soil contaminated with fungal spores onto the vine, entering the tissues through wounds or natural openings.

The severity of the disease is highly dependent on environmental conditions. Hailstorms are the most critical factor, as they cause physical injury to the berries, allowing the fungus to infect them easily. Combined with high temperature and moisture, the disease can spread rapidly through the vineyard, leading to significant yield losses if not managed promptly.

Management and control strategies include:

• Sanitation: Removing and destroying all infected plant material after the harvest.
• Protective Fungicides: Applying copper-based or specific anti-rot fungicides, especially after hail events.
• Canopy Management: Improving airflow and sunlight penetration through proper pruning and trellising.
• Pest Control: Reducing damage from insects and birds that can create entry points for the pathogen.