🪱 Root-Knot Nematode
Meloidogyne spp.
Invisible worms tying your roots into knots — literally.
How to identify
You can't see the worms themselves — they're microscopic, eel-shaped, and live in the soil. The diagnosis is the roots: pull a struggling plant and look for bead-like galls or knots swelling along the root system, sometimes with branched, stubby root tips.
Damage signs
Above ground, plants look thirsty and starved no matter how much you water or feed — stunted, yellowed, wilting in the afternoon heat. The knotted roots can't absorb water or nutrients, so the plant slowly fades while everything around it thrives.
Plants it attacks
Tomatoes, peppers, okra, cucumbers, beans, carrots, sweet potatoes, most vegetables
Non-chemical controls
- Solarize the bed: in summer, water deeply, cover with clear (not black) plastic sealed at the edges, and bake for 4–6 weeks — Florida sun turns the top inches of soil into a nematode sauna.
- Plant resistant varieties — look for the letter 'N' on tomato and pepper labels, which marks bred-in root-knot resistance.
- Sow French marigolds (Tagetes patula) as a cover crop for a full season; their roots exude alpha-terthienyl, a compound that suppresses nematode populations.
- Rotate with non-host crops like corn, grasses, or small grains for 2–3 years to starve the nematodes out — they can't wait forever.
- Pile on compost and organic matter; rich soil feeds the fungi and predatory microbes that hunt nematode eggs and juveniles.
- For badly infested spots, grow in fresh raised beds or large containers with clean soil mix and never let native soil splash in.
Nerdy fact: A single root-knot female can lay 500 or more eggs, and the galls are the plant being hijacked into building tumor-like feeding sites on command. Microscopic puppet masters.