Root-Knot Nematodes
Risk near you, next 48h
See whether your local forecast favours this disease right now.
When it strikes
Fix the cause, not the leaf
No spray will help here. The trigger is soil, water supply, nutrition or temperature, so change the growing condition and judge the result on new growth, not on damaged leaves.
Soil and crop debris
It waits in the ground or in last season's debris, so removing the plant does not clear the bed. Rotation and debris removal are the working controls.
It carries over to next season in soil, debris or seed — which is why rotation matters here, not just treatment.
Keep out of the compost
This survives a garden heap. Bag it for municipal green waste, which is composted industrially at temperatures a garden heap cannot reach, or burn it where that is permitted.
When and where to look
Scout the planting while temperatures hold between 18°C and 30°C.
Rule these out first
Same category, and at least one host crop in common — so they are genuinely confusable in the same part of the garden.
The signs that lead here
Full problem lists for these crops
About
Root-knot nematodes (Meloidogyne species) are microscopic roundworms that invade roots and force the plant to build galls around them. They are worst in light, sandy soil under glass and in polytunnels, where warmth lets several generations complete in a single season.
Symptoms
Plants wilt in the heat of the day despite adequate water, grow slowly and yellow between the veins. Lifted roots carry irregular swellings and galls fused into the root tissue — unlike legume nitrogen nodules, these cannot be rubbed off.
Organic Treatment
Remove infested plants with their whole root system. Grow a French marigold (Tagetes patula) green manure over the affected bed for at least two months and dig it in — this is one of the few well-evidenced botanical controls. Solarise the soil under clear plastic through high summer.
Chemical Treatment
Nematicides are not available for garden use. Control is cultural, and soil replacement is the only immediate fix under glass.
Prevention
Rotate widely, and use resistant rootstocks for greenhouse tomatoes — grafted plants marked VFN carry nematode resistance. Add organic matter, which supports the predatory soil fauna that suppress nematode numbers.
Crops at risk
Related problems
Root-Knot Nematodes risk by location
Each location has a month-by-month profile computed from the weather archive: how many hours a year actually meet this disease’s thresholds.