Splanchnonema argus

Splanchnonema argus is a fungal pathogen primarily known for causing bark necrosis and dieback in various species of willow (Salix). This ascomycete fungus acts as an opportunistic pathogen, colonizing the stems and branches of trees that are already stressed by environmental factors or mechanical injuries.

The visual symptoms of this infection include the appearance of small, raised black structures on the bark surface, which are the fungal ascostromata. As the infection progresses, the surrounding bark tissue becomes necrotic, often splitting or peeling away. This interferes with the tree's vascular system, hindering the transport of water and nutrients.

The development and spread of Splanchnonema argus are closely linked to high humidity and the presence of entry points such as frost cracks, sunscald, or pruning wounds. Spores produced by the fungus are disseminated during rainy weather, allowing the disease to spread rapidly within crowded or neglected willow stands.

The economic and aesthetic impact is significant, especially in landscape gardening and nurseries where the appearance of willow trees is highly valued. The disease leads to the progressive death of affected branches, and if the infection reaches the main trunk, the long-term survival of the tree is severely compromised.

Management and prevention strategies:

• Regular pruning of dead or infected branches to reduce the inoculum level.
• Prompt sterilization and protection of pruning cuts with fungicide-based sealants.
• Improving tree vigor through proper fertilization and irrigation to strengthen natural defenses.
• Applying copper-based fungicides as a preventative measure in early spring or autumn.