Tomato corky root rot

The fungus Pseudopyrenochaeta lycopersici is the causal agent of corky root rot in tomatoes. This soilborne pathogen primarily attacks the root system, severely impeding the plant's nutrient and water uptake capabilities, which directly affects growth vigor.

While tomatoes are the primary host, the fungus can also infect other solanaceous crops. Due to the formation of persistent resting structures known as sclerotia and pycnidia, the pathogen can remain viable in the soil for many years, making it particularly troublesome in intensive greenhouse production systems.

Symptoms are predominantly observed on the roots and include significant physical deterioration. The progression of the disease typically involves:

• Development of small, light-colored lesions that progressively darken and expand.
• Tissues becoming thickened, corky, and cracked as the infection advances.
• Severe reduction of functional fibrous roots.
• Stunted growth, chlorosis, and wilting of the aerial parts, especially during high transpiration periods.

Environmental factors play a crucial role in disease establishment. The fungus thrives in moist, cooler soils, with optimal development occurring between 15°C and 20°C. In greenhouses where monoculture is practiced without soil sterilization, the pathogen pressure tends to increase exponentially over time.

Effective management strategies focus on preventing the buildup of inoculum in the soil. Key practices include steam pasteurization or solarization of the growing medium, maintaining proper drainage to avoid waterlogged conditions, and utilizing resistant cultivars or rootstocks. Additionally, biological control agents such as Trichoderma species are used to suppress the pathogen's activity in the rhizosphere.