Root lesion nematode

Systematic position and type of pathogen: The root lesion nematode (Pratylenchus penetrans) belongs to the phylum Nematoda, family Pratylenchidae. It is a migratory endoparasitic nematode that lives and feeds within the roots of plants, causing significant structural damage to the vascular system of the host crop.

Diseases and host crops: This pathogen is notorious for its extremely wide host range, exceeding 400 species. It is a primary cause of root lesion disease, affecting potatoes, carrots, onions, strawberries, roses, and various fruit trees. The damage inflicted by these nematodes often predisposes plants to secondary infections by soil-borne fungi and bacteria.

Biology and life cycle: The life cycle consists of an egg stage, four larval stages, and the adult stage. Unlike some other nematode species, both juveniles and adults are capable of penetrating and leaving root tissues. They migrate through the root cortex, creating lesions as they feed on cortical cells and destroy the structural integrity of the plant roots.

Developmental conditions: Pratylenchus penetrans thrives in light-textured, well-drained soils, particularly sandy loams. They are most active within a temperature range of 15°C to 25°C. Because they can survive for extended periods in both soil and within the roots of perennial weeds, they are considered very difficult to eradicate once established in a field.

Harmfulness and control measures: Infestation typically manifests as stunted growth, wilting, and poor yield, often mimicking symptoms of nutrient deficiency. To manage this pest effectively, the following strategies are recommended:

• Implementing crop rotation with non-host crops or cover crops like marigolds (Tagetes) which release nematocidal compounds.
• Ensuring the use of certified, nematode-free planting stock.
• Managing weed populations that serve as alternative hosts during the off-season.
• Applying soil fumigation or integrated chemical control when threshold levels are exceeded.