White rot of grapevine

Coniothyrium diplodiella is a significant fungal pathogen known as the causal agent of white rot in grapevines. Taxonomically, it belongs to the phylum Ascomycota and is classified as a Coelomycete. This phytopathogen specifically targets damaged plant tissues, causing severe decay of berries, rachises, and shoots, which can lead to total crop loss if environmental conditions are favorable for its development.

The disease is characterized by the sudden wilting and discoloration of grapes. Affected berries initially turn pale or yellowish, then shrivel and dry out. One of the most distinct diagnostic signs is the emergence of numerous tiny, black pycnidia scattered across the surface of the infected tissue, which contain the spores of the fungus. The rot makes the fruit completely unsuitable for winemaking or fresh consumption.

The life cycle of the fungus centers on its ability to overwinter in infected grape debris, dead wood, and the soil. During periods of rainfall, the pycnidia release masses of pycniospores. These spores are disseminated primarily by splashing water or wind-blown droplets. The fungus is an opportunistic wound pathogen, meaning it requires breaks in the plant surface, such as those caused by hail or mechanical trauma, to enter and colonize the tissue.

Epidemiological factors for Coniothyrium diplodiella include high humidity and warm temperatures, typically between 20°C and 25°C. Severe outbreaks are most common following heavy thunderstorms and hailstorms, which inflict the necessary physical damage on the vines. The rapid infection process can occur within 24 to 48 hours following such weather events if the tissue remains moist.

• Immediate application of contact fungicides after hail events to protect wounded tissues.
• Sanitation practices such as removing and destroying all infected clusters and vineyard refuse.
• Improving vineyard aeration through proper canopy management and leaf thinning.
• Protecting vines from mechanical injuries during cultivation and soil operations.
• Regular monitoring of the vineyard, especially during the fruit ripening stages, to detect early symptoms.