Willow witches' broom

Willow witches' broom is a fungal disease caused by the ascomycete Taphrina epiphylla. This pathogen is a specialized parasite that primarily targets various species of the Salix genus, leading to dramatic physiological changes in the tree's growth pattern.

The hallmark symptom of this condition is the proliferation of dense, stunted, and sterile shoots originating from a single point, creating the appearance of a broom. Affected leaves are typically deformed, smaller than normal, curled, and exhibit chlorosis or reddish discoloration, often covered with a fine fungal spore coating on the underside.

Disease development is heavily influenced by environmental conditions, particularly cool and wet weather during the spring. The fungus survives the winter as mycelium within the host's buds and branches, allowing it to re-emerge annually and progressively colonize more areas of the tree crown.

The impact of this disease is significant as it depletes the tree's nutrient reserves and disrupts normal photosynthesis. Over time, the affected branches become brittle and die back, significantly reducing the ornamental value of the tree and, in severe cases, compromising the tree's overall structural health and longevity.

• Pruning out all infected branches, ensuring deep cuts into healthy wood to remove the internal mycelium.
• Disposing of all pruned material through burning or burial to prevent spore dispersal.
• Applying copper-based fungicides during the dormant season and early spring before bud break.
• Maintaining tree vigor through proper watering and fertilization to improve resistance.

Prevention is key, as managing established infections can be difficult. Nursery stock should be carefully inspected before planting, and regular maintenance checks are essential to identify and remove new outbreaks before they become systemic within the tree structure.