# Root-knot nematode

- URL: https://backyardgrapes.com/diseases/root-knot-nematode/
- Scientific name: Meloidogyne spp.
- Category: Insect / pest
- Affects: Roots
- Severity: moderate
- Favored by: Warm, sandy soils; spread in soil, irrigation water, and on tools; worse where vines follow vines.
- Easily confused with: Grape phylloxera, Crown gall

**Summary:** Microscopic soil roundworms that gall the roots and stunt vines, especially on sandy soils.

**What to look for:**
- Small galls and swellings along the roots (not the hooked tip-galls of phylloxera).
- Weak, stunted vines with yellowing leaves and drought-like stress despite watering.
- Patchy poor growth, worst on sandy soils and old replant sites.
- A slow, multi-year loss of vigour and yield.

**Treatment — Cultural / prevention:**
- Plant vines on nematode-resistant rootstocks — the most reliable defence.
- Avoid replanting vines straight after vines; fallow or rotate, and remove old roots.
- On a small scale, soil solarisation before planting reduces populations.
- Build soil organic matter to support the microbes that suppress nematodes.

**Treatment — Organic / low-toxicity:**
- Resistant rootstocks and soil health do the heavy lifting; some cover crops (e.g. certain mustards) help.

**Treatment — Conventional (chemical):**
- Pre-plant nematicides are used in commercial vineyards but are not practical for home growers.

Root-knot nematodes are microscopic roundworms that feed inside grape roots, causing them
to swell into small galls. Those galls disrupt the roots' ability to take up water and
nutrients, so infested vines behave like they're under drought stress — stunted, yellow,
and unproductive — even when they're watered. Damage builds slowly over years and is
usually patchy, hitting hardest on light sandy soils and on ground that has grown vines
before.

It's easy to confuse the root galls with phylloxera, but the two differ: phylloxera makes
hooked galls on the fine root tips, while root-knot swellings sit along the roots
themselves; crown gall, by contrast, makes one large tumour up at the crown or graft
union. Because there's no practical rescue treatment for a home grower, the whole strategy
is preventive: plant on resistant rootstocks, don't replant vines on tired vine ground
without a break, and keep the soil biologically healthy.

**Image credits:**
- Grape roots infected with root-knot nematodes; galling and swelling of the roots, with nematode egg masses stained red for visualisation — [Photo: Daniel Ng/UC Davis Viticulture, USDA Agricultural Research Service Image Gallery](https://www.ars.usda.gov/oc/images/photos/apr06/d466-1/)
- Galled grapevine roots with root-knot nematode egg masses (arrows), Meloidogyne vitis — [Photo: Yang et al., PLOS ONE (2021)](https://journals.plos.org/plosone/article?id=10.1371/journal.pone.0245201) (CC BY 4.0)
- Root-knot nematode galls on a crop root (not grapevine) — [Photo: David B. Langston, University of Georgia, Bugwood.org, Wikimedia Commons](https://commons.wikimedia.org/wiki/File:Meloidogyne_incognita_galls_(01).jpg) (CC BY 3.0 US)
- Root-knot nematode galls on tomato roots, shown for comparison (not grapevine) — [Photo: Plant pests and diseases (Flickr), Wikimedia Commons](https://commons.wikimedia.org/wiki/File:Tomato_(Solanum_lycopersicum)-_Root-knot_nematodes_-_38850656945.jpg) (CC0)

**Sources:**
- [Nematodes / Grape / Agriculture: Pest Management Guidelines](https://ipm.ucanr.edu/agriculture/grape/nematodes/) — UC IPM
- [Grape (Vitis spp.)-Nematode, Root-knot](https://pnwhandbooks.org/plantdisease/host-disease/grape-vitis-spp-nematode-root-knot) — Pacific Northwest Pest Management Handbooks (OSU/WSU/UI)
- [Nematodes](https://www.wineaustralia.com/growing-making/pest-and-disease-management/nematodes) — Wine Australia