White root rot fungus

Systematic position and type of pathogen: Rosellina necatrix belongs to the kingdom Fungi, class Sordariomycetes, and order Xylariales. It is a highly destructive soil-borne phytopathogen responsible for white root rot, affecting a vast array of woody plants, shrubs, and perennial crops globally.

Host range and diseases: The fungus is a polyphagous pathogen capable of infecting a wide variety of plants. Common hosts include pome and stone fruits such as apple, pear, and peach trees, as well as grapevines and various forest or ornamental species. The infection manifests as progressive decay of the root system, leading to canopy wilting and eventual plant death.

Biology and life cycle: The pathogen spreads through the soil primarily via mycelium and rhizomorphs—specialized hyphal strands that grow from infected roots to neighboring healthy ones. Its life cycle includes both asexual (anamorphic) conidial stages and sexual (telemorphic) perithecia formation, which allow the fungus to persist in soil and organic debris for extended periods.

Developmental conditions and impact: Rosellina necatrix thrives in soils with high moisture content and moderate temperatures. It typically enters the roots through wounds or direct penetration of the bark. The pathogen severely impairs the plant's vascular system, preventing the transport of water and nutrients, which often results in the sudden decline and death of the host.

Protection and control measures: Controlling this pathogen is challenging due to its long-term survival in soil. Key management strategies include:

• Selection of certified disease-free planting stock.
• Removal and destruction of infected plants and their entire root systems.
• Soil fumigation or solarization in nursery environments.
• Application of biological control agents such as Trichoderma species to suppress pathogen growth.
• Improving soil drainage to create unfavorable conditions for fungal development.