- Widespread. NOT in Oceania.
- Major disease of cultivated and wild yams; alternative hosts: cowpea, melon, sesame. Similar to Pratylenchus (see Fact sheet no. 8). Impacts: yield, quality, planting stocks.
- On tubers: initially, creamy-yellowish shallow rots beneath skin, resulting in dark brown, dry, powdery, <2cm-deep rots, causing cracking and flaking. Rots continue in storage.
- Nematodes enter sets/tubers as roots/shoots emerge or through cracks in skin. Spear in mouth used for entry and feeding. Males and females live and breed (lays eggs) in tubers and soil.
- Spread: in surface and ground water, and in soil on footwear and machinery/vehicles. Long distance in tubers. Survival in stored tubers, and on roots of other crops and weeds.
- Biosecurity: risk from unofficial introductions, trade in yams, and possibility of different strains. Official movement of germplasm should always follow the FAO/IPBGR Technical Guidelines.
- Biocontrol: none.
- Cultural control: carefully inspect tubers when cutting sets – do not plant sets with rots; disinfect knives frequently with bleach; coat sets in ash; avoid planting where yams grown previous season; avoid planting after alternative hosts; provide optimum nutrients for rapid growth; weed; after harvest, collect and burn diseased tubers; ideally, plant after fallow or legume cover crop.
- Chemical control: hot-water treatment. Immerse yams before cutting in 51°C for 10 minutes (use a thermometer). Test method on a few tubers, producing nematode-free planting material for next season’s crop.
