Plant Problem Diagnosis Key / Pests
Pest
Root-knot nematodes
Meloidogyne spp.
Microscopic roundworms that enter roots and make them swell into galls. Plants stunt and wilt in hot weather. Worst in warm, sandy soils.
Signs
- Round or spindle-shaped swellings that are part of the root and will not rub off.
- Patches of stunted, yellow plants that wilt in hot weather.
- Bean and pea nitrogen nodules look similar but rub off the root easily.
What favors it
Warm, sandy soil and repeated plantings of susceptible crops.
Prevention
- Grow resistant varieties, marked N on tomato seed packets.
- Rotate with less susceptible crops; some grains and grasses keep numbers down.
- Solarize beds under clear plastic for 6 to 12 weeks in summer.
Often confused with
Sources
- Root Knot Nematodes on VegetablesUniversity of Maryland Extension
- Root-Knot Nematodes in the Vegetable GardenClemson Cooperative Extension (HGIC)
- Control of Root-Knot Nematodes in the Home Vegetable GardenNC State Extension
- The Mi-9 Gene from Solanum arcanum Conferring Heat-Stable Resistance to Root-Knot Nematodes Is a Homolog of Mi-1Plant Physiology (research)
Treatment by crop
Cultural, biological and chemical options in the order to use them, and notes written for each crop.
Identification is free. Treatment is on the Home and Pro plans.
Questions in the key that lead here
- Look the plant over, leaf undersides included. Are insects, mites, slugs, eggs, webbing or droppings on it?
Yes, something living or its traces - What is on the plant?
Something on the roots - What is on the roots?
Knots and round swellings on the roots
Not a match? Start the key or describe what you see.
More photos
More from university Extension: search Extension pages on root-knot nematodes, or find a plant diagnostic lab through your state's Extension.
Other pests
- Aphids
- Bagworms
- Bark beetles of pine and spruce
- Broad mites and cyclamen mites
- Caterpillars
- Cicada and twig-cutting damage
- Colorado potato beetle
- Cucumber beetles
- Cutworms
- Elm leaf beetle
- Emerald ash borer
- Flea beetles
- Fungus gnats
- Galls on leaves and twigs
- Hemlock woolly adelgid
- Japanese beetles
- Lace bugs
- Leafminers
- Mealybugs
- Pine sawflies
- Root aphids
- Russet mites
- Sapsucker damage
- Scale insects
- Shore flies
- Slugs and snails
- Spider mites
- Spongy moth (gypsy moth)
- Spotted lanternfly
- Squash bugs and stink bugs
- Squash vine borer
- Tent caterpillars and fall webworm
- Thrips
- Whiteflies
- Wood borers