Planning reference

Root-Knot Nematodes vs Fusarium Wilt

Separate root-knot nematode root damage from Fusarium vascular wilt before composting plants, changing soil, grafting, solarizing, fumigating, or replanting nightshades.

What each nightshade wilt signal means

Root-knot nematodes
Root-knot nematodes are microscopic roundworms that feed inside roots, causing firm galls, weak root systems, patchy stunting, yellowing, and hot-weather wilt even when stems are not vascular-browned.
Fusarium wilt
Fusarium wilt is a soilborne vascular disease that plugs water movement inside susceptible tomatoes and other nightshades, usually showing lower-leaf yellowing, one-sided wilt, and brown vascular tissue in the lower stem.
Root galls, patchy stunting, and hot-weather wilt
Plants that are unevenly stunted in sandy or coarse beds, wilt during hot afternoons, and have swollen or knotted roots point toward root-knot nematodes instead of a stem-only diagnosis.
One-sided yellowing and dark vascular browning
Lower leaves yellowing on one side of a plant or leaflet, day wilt with partial recovery, warm soil, and brown streaks inside the lower stem point toward Fusarium wilt.
Dig roots, scrape stems, and sample soil before replanting
Pulling plants without checking roots can miss nematode galls, while diagnosing from roots alone can miss vascular wilt; pair a root inspection with stem scraping, crop history, resistant letters, and lab or soil sampling when the bed history matters.

Root and vascular wilt workflow

Do not diagnose from aboveground wilt alone
Do not treat every stunted or wilting tomato, pepper, eggplant, or potato as Fusarium wilt; inspect roots for firm galls, map patchy rows and sandy soil, scrape lower stems for vascular browning, check cultivar resistance letters, soil temperature, watering history, weed hosts, crop rotation records, and diagnostic-lab or soil-sampling needs before composting plants, grafting, solarizing, fumigating, or applying any product.
Map the bed pattern
Root-knot nematodes often show patchy damage where susceptible crops, sandy soil, and warm beds line up. Fusarium can also persist in soil, so compare row pattern with root and stem evidence.
Inspect roots and lower stems separately
Look for firm root galls and a reduced root system before calling nematodes; scrape or split a lower stem to look for dark vascular browning before calling Fusarium wilt.
Use resistance letters carefully
Tomato resistance letters can separate nematode resistance from Fusarium race resistance; do not assume an F letter protects against root-knot nematodes or that an N letter protects against Fusarium.
Plan prevention for the next crop
Once either problem is established, rescue options are limited. Use resistant cultivars, crop rotation, sanitation, weed-host control, soil health, solarization where locally appropriate, and diagnostic confirmation before major soil decisions.

Use these paths

Source basis