Pleurophoma leaf spot

The fungus Pleurophoma pleurospora (often referred to in the context of Phoma diseases of grapevine) is an ascomycetous fungus responsible for significant physiological damage to vines. This pathogen targets the vascular tissues and bark, leading to systemic weakness of the grapevine.

The primary host for Pleurophoma pleurospora is the cultivated grapevine (Vitis vinifera). While it primarily affects canes and older wood, it can also manifest on petioles and cluster stems if environmental conditions allow for the colonization of these tissues during the growing season.

Early symptoms involve the appearance of dark, necrotized spots on the surface of lignified canes. As the infection progresses, the bark may show signs of splitting or discoloration. Characteristic black pycnidia (fruiting bodies) emerge on the surface of the bark, which serve as the primary source of inoculum during subsequent wet weather events.

High humidity, frequent rain, and moderate ambient temperatures are critical for the spread of this pathogen. Spores are disseminated via water splash and wind, typically entering the host through existing wounds, pruning scars, or frost cracks. Inadequate canopy management, which leads to poor airflow and high moisture retention, significantly increases the risk of infection.

The economic impact of the disease is severe, as it causes the gradual dieback of cordons and eventually whole plants, reducing the lifespan and productivity of the vineyard. Management strategies focus on sanitation, such as removing infected wood during pruning, and the application of protectant fungicides to seal pruning wounds and prevent new infections during the vegetative period.

• Sanitary pruning to remove diseased wood from the vineyard.
• Applying wound sealants to large cuts to prevent entry.
• Improving canopy ventilation through proper shoot thinning.
• Preventative fungicide sprays during early spring and bud break.