Root Knot Nematode Control

Symptoms

Plants show patches of poor, stunted growth with yellowing leaves that wilt in the afternoon heat even when the soil is moist, looking like a nutrient or water shortage. The sure sign is on the roots, which carry many small to large knots or galls, swellings that cannot be rubbed off, unlike the helpful nodules of legumes. Affected plants flower and fruit poorly. The damage usually appears in scattered patches across the field.

Damage

Root knot nematodes, mainly Meloidogyne incognita, are microscopic soil worms that damage the roots of tomato, brinjal, chilli and capsicum and can cause yield losses of 20 to 60 percent or more in heavily infested soils. The galls block the roots from taking up water and nutrients, weakening the plant and making it more prone to wilt and other diseases. They survive long in the soil and build up under continuous solanaceous and vegetable cropping, so once established they are hard to remove.

Organic & cultural control

Apply neem cake or other oil cakes to the soil before planting, which is one of the most effective and farmer friendly nematode controls. Add well decomposed farmyard manure and soil bio agents like Pochonia chlamydosporia, Paecilomyces lilacinus or Trichoderma viride that attack the nematode. Grow marigold as an intercrop or in rotation as its roots suppress nematodes. Practice deep summer ploughing and soil solarisation in summer to kill nematodes, and follow crop rotation with cereals and non host crops.

Chemical control

Chemical nematicides are a last resort and must be used very carefully. Where recommended, a granular nematicide such as fluopyram or carbosulfan or fenamiphos may be applied to the soil at planting strictly as per label, as these products are toxic and need correct handling. Bio nematicide formulations of Paecilomyces or Purpureocillium lilacinum are safer options. Avoid carbofuran where banned or restricted. Always follow the product label dose, observe the pre harvest interval and consult your KVK or agronomist before using any nematicide.

Always follow the product label, the recommended pre-harvest interval, and your local KVK or agronomist. Pesticide approvals change, so verify before use.

Prevention

Use nematode resistant varieties or graft tomato onto resistant rootstock where available. Raise nurseries in clean, solarised or nematode free soil and use only healthy seedlings to avoid carrying nematodes to the field. Follow a long rotation with cereals, maize and other non host crops and avoid continuous solanaceous or okra cropping. Add neem cake and organic matter regularly, practice deep summer ploughing and solarisation, and grow marigold in rotation to lower nematode numbers over time.