Clitocybe

Clitocybe is a genus of fungi that includes several species, such as Clitocybe tabescens, which function as dangerous plant pathogens. They are primarily responsible for causing white root rot in woody plants, leading to severe economic losses in orchards and decorative tree nurseries worldwide.

The disease is caused by soil-borne fungal pathogens that invade the host through the root system. The mycelium grows along the roots, colonizing the wood and destroying its structural components, including lignin and cellulose. This process eventually disrupts the vascular system, preventing water and nutrient uptake.

Host plants typically include a wide range of fruit trees, such as apple, pear, peach, and citrus, as well as various ornamental shrubs. The pathogen thrives in soils that were recently cleared of forests or near decaying wood, as it easily colonizes old stumps and spreading roots.

Symptoms are often visible only when the infection is advanced. Key signs include stunted growth, chlorosis, and premature leaf drop. A definitive diagnostic feature is the presence of white, fan-shaped mycelial mats under the bark of the roots or the root crown, and clusters of mushrooms emerging from the base of the plant in late autumn.

Management strategies focus on sanitation and preventive measures. Infected trees must be completely removed, ensuring that as many roots as possible are extracted from the soil to prevent the spread of the mycelium. Improving soil drainage and maintaining tree vigor are crucial, as healthy plants are significantly more resistant to initial infections.