Rosellinia desmazieri

Rosellinia desmazieri is a specialized fungal pathogen responsible for causing significant damage to woody plants, particularly within the Salix genus. Classified as an ascomycete, this fungus acts as a necrotrophic parasite, invading the host tissues and triggering progressive necrosis. It is recognized as a serious threat in arboriculture and forest nurseries.

The primary hosts for this pathogen are various species of willow. The infection often begins at the root collar, where the fungus penetrates the protective layers of the bark. Due to its host-specific nature, nurseries growing willow for ornamental or industrial purposes are at the highest risk of experiencing severe outbreaks if sanitation protocols are neglected.

The symptoms of infection are characterized by the presence of a dark, felt-like mycelium appearing near the base of the stem or on the roots. As the disease advances, the host displays signs of water stress, such as leaf chlorosis, thinning of the canopy, and the dieback of branches. If left unchecked, the complete girdling of the stem base occurs, leading to the rapid decline and death of the plant.

The development and spread of Rosellinia desmazieri are strongly influenced by high soil moisture and poor drainage. The fungus persists in the soil and on infected plant debris, utilizing moisture as a primary vehicle for spore dissemination. Dense planting and high humidity provide the ideal microclimate for the fungus to flourish and colonize new, healthy root systems.

Management strategies focus on a combination of cultural and sanitary measures. It is crucial to remove and destroy all infected plant material, including the root ball, to eliminate the source of the inoculum. Improving soil drainage and ensuring adequate spacing between trees are vital to reducing the infection risk. While chemical intervention with fungicides may be considered, long-term success relies on maintaining optimal tree vigor and strict adherence to hygiene standards.