Tomato corky root rot

The causative agent of this disease is the fungus Pyrenochaeta nobilis (also identified as Pyrenochaeta lycopersici). It is a soil-borne pathogen responsible for the classic corky root rot in tomatoes, which severely impairs the root system's ability to transport water and essential nutrients to the leaves and fruits.

Tomato plants are the primary host for this fungus. It is specifically problematic in greenhouse operations where tomatoes are continuously grown in the same soil or non-sterilized substrates. While other solanaceous crops can occasionally be affected, the economic impact is most profound in commercial and home tomato production.

Initial symptoms on the roots appear as yellowish-brown lesions that eventually develop into characteristic brown, corky, and cracked tissues. As the disease progresses, the root system becomes heavily decayed. Above-ground symptoms include stunting, midday wilting, and yellowing of the foliage, eventually leading to a significant reduction in overall plant vitality.

The development of Pyrenochaeta nobilis is favored by cool to moderate soil temperatures (15°C to 20°C) and high soil moisture levels. The fungus is highly persistent in the environment due to the formation of pycnidia and sclerotia, which can remain dormant in the soil or crop debris for several years, ensuring infection risk for future crops.

Economic damage is substantial, often resulting in lower fruit quality and diminished yields due to impaired plant uptake. Prevention and control strategies are essential for greenhouse management:

• Implementing crop rotation with non-host plants to break the disease cycle.
• Steam sterilization or solarization of the greenhouse soil before planting.
• Using resistant tomato varieties or rootstocks.
• Ensuring proper sanitation practices to prevent the movement of contaminated soil into the greenhouse.