Willow scab

Willow scab is a fungal disease caused by Venturia chlorospora, which primarily affects various species of willow trees. As a specialized pathogen, it exploits the host's vulnerability during moist spring conditions, leading to significant physiological stress in the trees.

The characteristic symptoms include dark, necrotic spots on the leaves, which often spread to petioles and young stems. As the infection progresses, the foliage begins to wither, curl, and drop prematurely, leaving the branches bare and susceptible to further damage.

The spread of the disease is highly dependent on environmental factors, particularly humidity and rainfall. The fungus overwinters in dead leaves and infected twigs, releasing spores that are easily disseminated by wind and splashing water when temperatures are moderate in the spring.

The economic and aesthetic impact of willow scab is severe, as it reduces the photosynthetic capacity of the tree. Continuous defoliation weakens the willow, making it less vigorous and more prone to secondary infections from other pathogens or pests that thrive on stressed plants.

Effective management requires a combination of sanitation and chemical interventions. Removing and disposing of fallen leaf litter is crucial to reduce the primary inoculum level. In addition, periodic application of fungicides during the active growth phase can successfully prevent or suppress the infection.

• Sanitary pruning of infected twigs and branches.
• Removing and destroying infected leaf debris.
• Fungicidal sprays applied at bud break.
• Improving air circulation to reduce humidity around the foliage.