Pest

Root-knot nematodes

Microscopic soil worms that cause knobby swellings on roots, so plants wilt in the heat and stay small.

What you'll see

• Plants are stunted and yellowish, and wilt in the afternoon heat even when the soil is moist.
• Dig a plant up: the roots carry round knots or swellings, from pinhead size up to 1 inch (2.5 cm) across.
• The knots are part of the root and won't rub off, unlike the nodules on beans and peas.

Why it happens

Root-knot nematodes are tiny roundworms that enter roots and feed inside them, forming galls that block water and nutrients. They build up when the same crops grow in the same spot year after year.

How to fix it

1. Pull up affected plants, roots and all, right after harvest, and throw them away.
2. In the hottest weeks, solarize the bare bed: till and wet the soil, then cover it with clear plastic for 6 to 12 weeks.
3. Grow crops nematodes don't attack, such as corn, onions or garlic, in that spot for the next few years.

Keep it from coming back

• Grow resistant varieties, such as tomatoes labeled N.
• Rotate crops so susceptible ones aren't grown in the same bed each year.
• Add organic matter to the soil each season to support healthy roots and soil life.

Sources

• UC IPM: Nematodes
• University of Maryland Extension: Root knot nematodes on vegetables
• Clemson HGIC: Root-knot nematodes in the vegetable garden

General guidance, not a diagnosis. For valuable, edible or outdoor crops, check with a local extension service or plant expert. Use any product exactly as its label says, and keep children and pets away while it dries.