Lesion nematode

Pathogen and disease type: Lesion nematodes, belonging to the genus Pratylenchus, are migratory endoparasitic roundworms. They are considered one of the most economically damaging groups of plant-parasitic nematodes globally. By invading the cortical tissues of roots and tubers, they cause significant cellular damage, which leads to various necrotic lesions and systemic plant weakness.

Affected crops: These nematodes exhibit an extremely wide host range, making them a major challenge in modern agriculture. They severely impact potatoes, causing deep lesions and skin defects in tubers, and pose a significant threat to Citrus orchards, where they weaken the root system, ultimately leading to decline and reduced yields in trees.

Symptoms and signs: The visual symptoms are characterized by stunted growth, chlorosis, and wilting, often resembling nutrient deficiencies. The most distinctive signs, however, are found below ground: small, dark-brown or black lesions appear on the root cortex, which can coalesce to destroy the entire root system. In potato tubers, the presence of the nematode causes superficial browning, scabbing, and cracking of the skin.

Conditions for development: Lesion nematodes thrive in well-aerated, moist soils. They can survive in both soil and plant tissues, enduring adverse conditions by migrating between roots. The rate of reproduction is strongly dependent on temperature and host suitability. Once the root system is compromised, the weakened tissues become highly susceptible to secondary colonization by soil-borne fungi and bacteria.

Control and prevention: Managing lesion nematodes requires an integrated strategy to minimize their impact. Key practices include:

• Planting nematode-free, certified seed tubers or seedlings.
• Implementing long-term crop rotation schemes using non-host crops.
• Utilizing cover crops with nematicidal properties, such as certain varieties of radish or mustard.
• Applying chemical nematicides or soil fumigants where populations exceed established economic thresholds.
• Maintaining high soil organic matter to promote beneficial microbes that may naturally suppress nematode populations.