White rot of grapevine

The causal agent of white rot in grapevines is the fungus Coniella diplodiella. This pathogen is a serious threat to viticulture, primarily known for causing significant decay of grape clusters during the summer growing season.

The fungus affects various parts of the grapevine, including berries, rachises (cluster stalks), and young shoots. While it can colonize various tissues, its impact on the berries during the ripening phase is the most economically damaging, leading to total loss of affected clusters if left unmanaged.

The initial symptoms are characterized by light-colored, watery spots on the berries, which quickly turn light brown or greyish. In advanced stages, the berries become shriveled and appear bleached or "boiled." A diagnostic feature of this disease is the development of numerous tiny, black, pimple-like structures called pycnidia on the surface of the infected tissue.

Development and spread of the pathogen are highly dependent on environmental conditions, specifically high humidity and warm temperatures. The fungus typically requires a wound to infect the plant, which makes vineyards extremely susceptible following hail storms, heavy rainfall, or insect damage that breaks the berry skin.

Integrated pest management is essential for controlling Coniella diplodiella. Strategies include:

• Proper canopy management to improve airflow and reduce humidity.
• Sanitation, including the removal and destruction of infected clusters and debris.
• Control of secondary pests that may cause mechanical damage to berries.
• Preventive fungicide applications immediately after hail events or during prolonged rainy weather.