Hektar

Tomato Root Rot Disease
Causative Pathogen
The disease is caused by Fusarium oxysporum f.sp. radicis-lycopersici 

Disease Symptoms (Key Diagnostic Characteristics)

• Lesions appear on the stems of infected plants, extending 5-20 cm above ground level, with occasional "cancerous" ulcerations near the vascular bundles. These are soon followed by a white mycelium, which later turns pink-orange.
• The primary symptom is observed in the root system, where browning and rot affect both the roots and vascular bundles. Infected plants show withering, and the root system becomes smaller, brown, and decayed.
• When the stem is sectioned, the conducting vessels display a chocolate-brown discoloration extending 5-25 cm from the soil level.

Favorable Conditions for Disease Development and Spread

• This soil-borne pathogen is commonly found in areas where tomato monoculture has been practiced in poorly drained, heavy soils over many years.
• The pathogen can survive in infected plant debris left in the soil.
• Irrigation water serves as the primary medium for pathogen dissemination within crops.
• The fungus Fusarium oxysporum f.sp. radicis-lycopersici proliferates optimally at temperatures around 20ºC, whereas Fusarium oxysporum f.sp. lycopersici prefers soil temperatures between 25-30ºC.

Prevention and Control Measures

• When clearing tomato crops, ensure all plant roots are fully removed, leaving no residue in the soil.
• Maintain soils with excellent drainage.
• Avoid overwatering, especially on clay soils.
• After several years of tomato monoculture in greenhouses (which may turn soil into a "reservoir of pathogens," severely reducing crop yield), disinfect the soil with Sodium Metam-based products like Nemasol 510 at a dose of 700 liters/ha.
• After 5-6 years of continuous monoculture, apply alternative treatments with Thiophanate methyl through drip irrigation. Begin treatment at planting and, if necessary, repeat 1-2 times at 3-4 week intervals, using the maximum recommended dosage.
• In the event of an outbreak, consider light mulching or adding peat or compost to the plant bed, with regular moistening to promote the development of adventitious roots. Support this with nutrient-rich soil amendments (both root and foliar) and short, frequent watering to maintain plant turgidity for an extended growing period.