Root-knot nematodes are microscopic worms that make galls on roots and choke water uptake.
Signs
Patches of weak, yellowing, wilting plants that do not respond to water or fertilizer. Dig a plant: swollen, knotted roots (not to be confused with the soft nodules of legumes) confirm them.
Management
- Rotate with non-host crops such as cereals, or with nematode-suppressing crops (marigold, some brassicas, sorghum-sudan).
- Resistant varieties and rootstocks, especially in vegetables.
- Add organic matter to encourage natural enemies.
- Soil solarisation in hot seasons: clear plastic over moist soil for several weeks.
- Sanitation: clean tools and boots, and remove roots after harvest rather than leaving them to feed the population.
Nematicides are costly and restricted, so rely on prevention.
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