Willow rust

The causative agents of the disease are fungi of the genus Melampsora, including such species as M. larici-epitea, M. caprearum, M. epitea, and M. americana. These are heteroecious pathogens requiring the presence of an intermediate host from coniferous species to complete their life cycle.

Primary symptoms appear in early summer as yellow spots on the upper leaf surface, followed by the formation of bright orange uredopustules on the underside. By autumn, these are replaced by dark brown or black teliospores. Severe infestation causes premature leaf fall, which reduces plantation yields by 30–40%.

A specialized race classification of the pathogen is absent due to the high genetic variability of the populations. The resistance of willow cultivars is determined by genotypic features and is associated with the functioning of NBS-LRR genes, while breeding and cultivation practices are oriented toward the use of multi-clonal mixtures.