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Root-knot nematodes
Disease Meloidogyne
Damaged roots or bulbsKnots, galls, or swellingsWilting or dying plantsYellow, curled, or mottled leaves
How to spot it
Plants are stunted and yellow and wilt in the heat even when watered. The roots have round knots and swellings. On beans and peas, the helpful nitrogen nodules rub off easily; root-knot galls don't.
What it does
Tiny soil worms feed inside the roots, so plants can't take up water. Worst in sandy soil in the South.
What to do now
- Pull plants with their roots at the end of the season.
- Heat the soil under clear plastic in summer (solarizing).
Keep it away next time
- Grow resistant varieties ("N" on tomato tags).
- Plant a cover of French marigolds or cereal rye where it was bad.
- Add plenty of compost.
Plants it affects
Not sure? Your county extension office can identify it from a photo or sample, often for free.