Potato (Solanum tuberosum)-Nematode, Potato Rot

Cause Ditylenchus destructor is known only from a small area in Idaho. The main problem is in storage where infected tubers rot, which spreads the disease to other tubers.

Symptoms No aboveground symptoms. Early tuber symptoms are pinhole-size lesions; these enlarge to gray patches, which become dry, granular, and cracked. Infected areas become brown and soft, detectable more readily by touch than sight. Secondary invasion by other microorganisms results in a generalized dark brown rot.

Sampling This nematode is rare in isolated regions. Sampling specifically for it probably is not necessary unless there is a history of it in the area. Soil samples alone should be sufficient. If this nematode is suspected in potatoes, submit both affected tubers and soil for testing.

Cultural control

  • Use clean seed pieces.
  • Place only healthy tubers in the storage.
  • Dust potatoes in storage with freshly slaked lime (4 kg/ton) to prevent the spread of infection.
  • Harvest early.
  • Use resistant variety if available.
  • Do not plant potatoes in infested fields for several years, and include cereal grasses and corn in the rotation.
  • Good weed control is important, especially to eliminate good hosts such as dandelion, clover, plantain, goldenrod, vetch, and wild carrot.

Chemical control Preplant fumigation.

  • Metam sodium (Vapam HL) at various rates. See label for details. Restricted-use pesticide.