Pleurostoma dieback

Pleurostoma dieback is a destructive wood disease of grapevines caused by the fungal pathogen Pleurostoma richardsiae. This fungus belongs to a group of pathogens involved in grapevine trunk diseases, which colonize the woody parts of the vine and severely compromise its vascular system over time.

The fungus is a typical opportunistic pathogen affecting Vitis vinifera. It primarily invades the plant through open wounds, such as pruning cuts or injuries caused by mechanical damage. Once established, the mycelium spreads slowly through the xylem vessels, obstructing water and nutrient flow to the canopy.

Early symptoms include stunted growth of shoots, leaf chlorosis, and the failure of grape clusters to develop fully. As the disease progresses, the vine experiences progressive dieback. Upon examination, cross-sections of the wood reveal diagnostic brown to black discolored streaks or circular patterns, indicating necrotic tissue.

The spread of the disease is facilitated by environmental factors such as high humidity and rain, which favor spore dispersal from infected wood. The pathogen can remain viable in infected debris for several years, making vineyard sanitation critical. Temperature fluctuations that weaken the vine also predispose the plants to easier colonization.

Management of this condition focuses on preventing the entry of the fungus into the plant. Control measures are primarily preventive and include:

• Sterilizing all pruning tools between vines to prevent cross-contamination.
• Protecting pruning wounds immediately after cutting with fungicides or pruning sealants.
• Removing and destroying heavily infected wood from the vineyard to reduce inoculum levels.
• Maintaining vine health through proper irrigation and fertilization to boost systemic resistance.