Dematophora root rot

Dematophora root rot is a severe fungal disease caused by the pathogen Dematophora arcuata, which represents the anamorph of Rosellinia necatrix. This fungus is widely recognized as one of the most destructive soil-borne pathogens affecting the root systems of numerous perennial crops and woody species.

The host range of this pathogen is extensive, including pome fruits like apples and pears, stone fruits, citrus, grapevines, and various ornamental trees. Because the fungus thrives in the soil for extended periods as mycelial mats or sclerotia, it is notoriously difficult to eradicate once it has become established in an orchard.

Symptoms of the infection typically begin below ground and progress until they affect the foliage. Visible signs include chlorosis, leaf drop, and stunted growth of the branches. In advanced stages, a characteristic white, mycelial growth can be observed on the root collar and bark. The root tissues eventually become dark, mushy, and emit a distinct odor, leading to the total decline of the host plant.

The development and spread of Dematophora arcuata are heavily dependent on environmental factors, particularly high soil moisture, poor drainage, and cool to moderate temperatures. The fungus spreads easily through physical contact between healthy and infected roots, or via the movement of infested soil and contaminated nursery stock.

Control strategies for Dematophora root rot focus primarily on prevention and sanitation. Growers are advised to select well-drained sites for planting, utilize certified pathogen-free nursery stock, and implement rigorous quarantine measures when moving equipment between plots. Infected trees should be removed along with their entire root system, and the surrounding soil may require solarization or chemical treatment to reduce the inoculum level.