Iris, Bulbous (Iris spp.)-Nematode, Potato Rot

Latest revision: 
March 2023


Cause A nematode, Ditylenchus destructor, that lives in soil and can be carried in bulbs. It is rare and only in isolated regions.

Symptoms Symptoms may vary, depending on variety. Leaves may be stunted or lacking. Gray or yellow areas may appear on the lower stem where it attaches to the bulb. On bulbs, a dark crevice separates the basal plate and outer fleshy scales. Yellow, gray, or black streaks are present especially in the outer fleshy scales, usually beginning at the base. Streaks may coalesce, and the entire scale or bulb may rot. The basal plate is gray and honeycombed.

Sampling Sampling specifically for this nematode probably is not necessary unless there has been a history of it in the area. Soil samples alone should be sufficient before planting. If this nematode is suspected in current iris plantings, submit both affected tubers and soil for testing.

Cultural control

  • Harvest infected stock 7 to 10 days early.
  • Destroy infected bulbs and debris.
  • Use at least a 2-year rotation.
  • Do not plant in infested soil.

Chemical control Preplant soil fumigation.

  • Telone II is registered at various rates depending on planting depth and soil type. See label for details. 5-day reentry. Restricted-use pesticide.

Reference Haglund, W.A. 1983. Efficacy of selected nonvolatile nematicides on control of Ditylenchus destructor in Iris. Journal of nematology, 15:92-96.