Willow scab

The causal agent of this disease is the fungus Venturia saliciperda. It is a severe ascomycete fungus that causes wilting and death of young shoots and foliage, commonly known as willow scab or black canker.

The disease primarily targets various species of the genus Salix. It is particularly devastating to ornamental weeping willows and basket willows grown in moist environments. Younger trees are often more susceptible to the systemic damage caused by the fungus.

Initial symptoms include dark spots on leaves, which rapidly turn black and lead to leaf shriveling. As the infection progresses, young shoots develop brown, sunken lesions or cankers. This often results in the characteristic "hooking" or curling of the branch tips as the tissue dies.

The fungus thrives in cool, wet spring weather. Spores are dispersed by rain splash and wind, infecting newly emerged leaves and shoots. Poor air circulation and high humidity within the tree canopy significantly contribute to the rapid development and spread of the pathogen.

The economic and aesthetic impact is significant, as the disease can lead to severe dieback, loss of vigor, and eventual tree mortality. Repeated cycles of infection weaken the tree's structure and make it highly prone to secondary attacks by other pests or pathogens.

• Prune and destroy all infected branches and twigs during dormancy.
• Apply protective copper-based or systemic fungicides during bud break.
• Maintain proper plant spacing to ensure adequate air circulation.
• Clear and remove all fallen leaf litter from the site to reduce overwintering spores.