Willow rust

Melampsora ferrinii is a specialized fungal pathogen causing willow rust. This disease belongs to the group of rust fungi that primarily affect various Salix species, disrupting normal physiological processes within plant tissues.

The causative agent belongs to the class of Basidiomycota. Throughout its life cycle, the pathogen produces specialized spore structures on leaves and young shoots. The fungus overwinters on fallen leaves and plant debris as teliospores, which serve as the primary source of infection for new growth in the spring.

Initial symptoms appear as small yellow or orange spots on the upper surface of leaves. As the disease progresses, orange pustules containing urediniospores form on the underside of the leaf, leading to premature yellowing and leaf drop. Severe infections often cause significant deformation of young shoots and stunted tree growth.

Favorable conditions for the development and spread of the disease include high humidity and moderate temperatures ranging from 15 to 22 degrees Celsius. During periods of heavy or persistent rain, spores are easily dispersed by wind and splashing water, causing widespread infection throughout entire willow plantations.

The economic impact of willow rust is characterized by reduced photosynthetic efficiency, which weakens the tree and diminishes its winter hardiness. Management and control strategies include:

• Sanitation, specifically the removal and destruction of fallen leaves in autumn to eliminate the primary inoculum.
• Proper spacing and canopy management to improve airflow and reduce humidity around the foliage.
• Application of copper-based or systemic fungicides upon the early detection of symptoms.
• Utilizing resistant willow cultivars when establishing new plantations to prevent disease outbreaks.