Divisi
Plant-parasitic nematodes
· Nematode
Photo: CSIRO · CC BY 3.0
Plant-parasitic nematodes are microscopic, thread-like roundworms that live in the soil and feed on plant roots. Root-knot types swell the roots into knots and beads; lesion, cyst and burrowing types cause dark rots, forking and dieback. Either way they choke the roots' ability to draw up water and food, stunt the plant, and open the door to soil fungi and rots. They survive in the soil and in infected seedlings and suckers for years.
Plant pests and diseases · CC0 
Public domain · Public domain
Why it matters
Nematodes are worms too small to see that attack your crop's roots underground, so the plant slowly starves even when you feed and water it well. A bad infestation can cost you up to half your harvest of tomato, potato, carrot, banana or okra. The worst part is that they hide in the soil and in infected seedlings for years — once a field is infested you cannot simply spray them away, you have to keep clean land clean and starve the worms down over several seasons. That is why spotting the sick patches early, and never carrying soil or seedlings from a bad field to a clean one, matters so much.
When to act
Patches of stunted, wilting plants with galled or lesioned roots on lifting a sample; a history of nematode damage in the field.
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 plant-parasitic nematodes field guide
- Identify it
- Scout for it
- Control it
14 field-guide sections in the app
The full guide to plant-parasitic nematodes — 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 plant-parasitic nematodes?
What you notice first (above ground): irregular patches of the field — not the whole field, and never neat along the rows — where plants are stunted, pale or yellow and wilt in the midday heat even when the soil is still wet. Early on they perk up again in the cool of evening; later they stop recovering at all. The give-away: these plants stay hungry-looking even after you add fertiliser, because the damaged roots can no longer drink it up. The same bad patches come back in the same spot season after season.
When should I take action against plant-parasitic nematodes?
Patches of stunted, wilting plants with galled or lesioned roots on lifting a sample; a history of nematode damage in the field.
How do I control plant-parasitic nematodes?
Prevent first — plant a resistant variety (your single strongest move). Where you can buy them, plant nematode-resistant varieties or rootstocks, such as root-knot-resistant tomato lines. "Resistant" means the plant has been bred to fight the worm off by itself — you spray nothing, the seed does the work. Of everything here this is the most reliable protection you have, so ask your seed supplier for it by name.
Which crops does plant-parasitic nematodes affect?
Among the crops covered here: Carrot, Enset, Okra, Pineapple, 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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