Botryosphaeria dieback

Causal agent and disease type. Diplodia seriata is the causal agent of a serious wood-infecting disease known as Botryosphaeria dieback. This fungus is a systemic pathogen that invades the vascular tissues of woody plants. It acts as an opportunistic parasite, colonizing the plant's internal structures and disrupting the flow of water and nutrients.

Host range. While this disease is a significant threat to viticulture (grapevine Vitis vinifera), its host range is remarkably broad. It affects a wide array of woody species, including apple trees, pears, walnuts, and various ornamentals. Because it can survive on many plants, it poses a recurring challenge for diversified orchards and vineyards.

Symptoms and signs. The primary symptom is the gradual decline of permanent wood, often manifested as cordon dieback. Internal examination of the vine trunks or cordons usually reveals characteristic wedge-shaped necrotic lesions (brown or black discoloration). In humid weather, small black fruiting bodies called pycnidia develop on the dead bark surface.

Conditions for development. Infection usually occurs through natural openings, pruning wounds, or winter-damaged tissues. The fungus requires moisture to release its spores, which are then spread by rain splash or wind. High humidity levels combined with moderate temperatures accelerate the germination and colonization processes within the plant tissue.

Harmfulness and protection. The disease is highly destructive as it permanently damages the plant's structural vascular system, often leading to sudden collapse, known as apoplexy. Control measures are focused on reducing inoculum levels and preventing new infections:

• Sanitary pruning to remove all infected wood during dry weather.
• Painting large pruning wounds with protective sealants or fungicides.
• Sterilizing pruning tools between vines to prevent cross-contamination.
• Promoting overall vine vigor through appropriate irrigation and soil management.