Dematophora root rot

Dematophora root rot, caused by the fungus Dematophora necatrix (asexual stage of Rosellinia necatrix), is a devastating soil-borne disease affecting the roots of a wide range of woody plants. It is commonly referred to as white root rot due to the distinct fungal growth observed on infected roots.

The host range for this pathogen is extensive, including fruit trees such as apple, pear, peach, and stone fruits, as well as grapevines and various ornamental shrubs. It is particularly problematic in established orchards and nursery settings where the soil environment remains stable for long periods.

Symptoms initially appear as a general decline in the health of the tree. Foliage may become chlorotic, sparse, and stunted, often followed by premature wilting or sudden death of the tree. Below ground, the roots are heavily colonized by a dense, white, cottony mycelial mat. Eventually, the root bark and underlying tissues decay, becoming soft and friable, which prevents the tree from anchoring and absorbing nutrients.

Favorable conditions for the pathogen include heavy, waterlogged soils with poor drainage. The fungus spreads through the soil via mycelial strands that bridge the gap between root systems. It persists in the soil on decaying organic matter, making it extremely difficult to eradicate once it has become established in an orchard site.

• Removing and destroying infected trees, including as much of the root system as possible.
• Implementing effective soil drainage systems to reduce water stagnation.
• Fumigating infested soil areas before replanting to reduce pathogen inoculum.
• Using certified, disease-free planting material to prevent introduction.
• Practicing rigorous sanitation and avoiding the movement of infested soil or plant debris.