Divisi
Root-knot nematode
Meloidogyne incognita · Nematode
Photo: Plant pests and diseases · CC0
Root-knot nematode (Meloidogyne incognita) is a microscopic, worm-like animal that lives in the soil, far too small to see with your eyes. Its young burrow into plant roots and make them swell into knobbly knots or 'galls', so the roots can no longer draw up water and food, and the plants above go stunted, yellow and wilt. It breeds fastest in warm, light sandy soils and can survive in the ground for years, spreading on infested soil, water and seedlings.
David B. Langston, University of Georgia, Bugwood.org · CC BY 3.0 us 
Plant pests and diseases · CC0
Why it matters
Root-knot nematode is a hidden root pest that can take up to 60% — more than half — of your crop of tomato, pepper, okra, carrot, cucumber, potato or beans. You rarely see it coming: it works underground, choking the roots, so by the time the plants are stunted and wilting the damage is already done. Worst of all, once it is in your soil it stays there for years and rides from bed to bed on soil, water and seedlings — and there is no quick spray that can save the crop. Keeping it out, and starving it with rotation, is far easier than getting rid of it.
When to act
patches of stunted, wilting plants, or galls found on roots of sampled plants
This guidance is general, compiled from published agronomic references including FAO and CABI. Thresholds and timing shift with your crop, your variety and the season.
In much of the region a spray is simply called mushonga — medicine. But a chemical group you cannot name is one you cannot rotate, and a product you did not write down has no pre-harvest interval you can observe. Mushonga, and other farming words →
The full root-knot nematode field guide
- Identify it
- Scout for it
- Control it
17 field-guide sections in the app
The full guide to root-knot nematode — every symptom to check, how and when to walk your field looking for it, and the controls that actually work, ranked. Built into your crop plan, so you are told to look before it costs you a harvest.
Crops it affects
Frequently asked questions
How do I identify root-knot nematode?
The first thing you see (above ground): a patch of plants that are stunted and yellow and wilt in the midday heat even though the soil is wet and you have watered — then perk up again in the cool of evening. The patch is uneven — sick plants sitting right next to healthy ones, not the whole field failing evenly.
When should I take action against root-knot nematode?
patches of stunted, wilting plants, or galls found on roots of sampled plants
How do I control root-knot nematode?
Prevent — best of all, plant a resistant variety. Where you can get them, grow nematode-resistant varieties or grafted rootstocks (for example Mi-gene resistant tomatoes — a type of the same crop bred to shrug the pest off). This is the single most powerful thing you can do; it stops most of the attack before it even starts.
Which crops does root-knot nematode affect?
Among the crops covered here: Carrot, Cucumber, Okra, Tomato.
Catch it before it costs you a harvest
Divisi builds scouting into your crop plan — it tells you when to walk your field, what to look for at that stage, and what to do when you find it. Free for farmers, works offline.
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