Root-knot nematode

Meloidogyne chitwoodi and Meloidogyne fallax

Symptoms

• Superficial lumps or blotches just below the skin
• Brown spots (corky cells) in the centre of the tuber
• Nematodes can be present deep in the tuber (often near the vascular bundle ring

Root symptoms

• Very small, elongated club-shaped swellings

Infection and spread

• Nematodes survive in the soil, roots and tubers
• Seed tubers
• Very extensive list of host plants (including weeds)
• Crop rotation has little effect on the nematode
• Irrigation from early July increases tuber infestation
• Maize is a host plant for Meloidogyne fallax
• Nematodes remain active at temperatures above 5° C
• The infestation of the tuber can also increase during storage.

Possible confusion with

• Powdery scab (Spongospora subterranea)