Xylaria root rot

Xylaria mali is a pathogenic fungus responsible for a destructive type of root rot in fruit trees. It colonizes the roots and the crown of the tree, causing the decay of vascular tissues and leading to the eventual decline and death of the plant.

This pathogen primarily targets apple trees, but its host range may include other pomaceous and stone fruits. Trees under environmental stress, such as waterlogged soil or those with root injuries, are significantly more susceptible to infection by this opportunistic fungus.

The early symptoms of the disease are often nonspecific, resembling general nutrient deficiency: sparse canopy, yellowing foliage, and progressive branch dieback. A definitive sign occurs when the tree is severely compromised, revealing white mycelial growth beneath the bark of the roots or the presence of black, club-shaped stromata growing near the base of the trunk.

The development of the fungus is favored by high soil moisture levels and poor aeration. The pathogen survives in the soil on decaying organic matter and woody debris. Infection spreads through direct contact between the healthy roots of a tree and the infected root debris or neighboring infected trees.

• Total removal and destruction of infected trees, including root systems.
• Sanitization of the planting site to eliminate remaining inoculum.
• Improvement of soil drainage to prevent water accumulation.
• Careful handling of the root zone to avoid wounds.
• Regular monitoring of orchard health to detect signs of early decline.

Management of Xylaria root rot is challenging because once the fungus has established itself deep within the root system, curative treatments are rarely successful. Maintaining site hygiene and ensuring optimal growing conditions remain the primary defense mechanisms against this destructive soil-borne pathogen.