Jerusalem Artichoke (Helianthus tuberosus)-Southern Blight

Cause The fungus, Athelia rolfsii (syn. Sclerotium rolfsii). This fungus has a very wide host range and has recently appeared in vegetable crops in western Oregon. Tomato, peppers, eggplant, potato, soybean, grasses including corn and wheat, alfalfa, clover, asparagus, beet, Brassica crops (broccoli, cabbage, kale, etc.), beans, carrot, cucumber, melons, pumpkin, squash, sweet potato, lettuce, chicories, garlic, onion, rhubarb, cuttings of woody tree fruit including apple, and a wide-range of herbaceous and woody ornamentals are among the many plant types susceptible to southern blight. Small, round survival structures of the fungus, called sclerotia, allow the fungus to persist for years in soil. Warm (> 59°F, 81°F to 86°F is optimum), wet, acidic soils are conducive for disease outbreaks.

Symptoms Plant stems turn brown, starting at or below the soil line and decay moves upwards. Leaves turn brown and plants eventually die stem by stem, typically over several weeks to a couple of months. A white moldy growth usually develops on the base of infected stems and may appear on the soil surface immediately surrounding infected plants. Small, reddish-brown to light-brown, mustard seed-like structures commonly form on this white moldy growth, especially along the base of infected stems, and can be seen on plant portions below the soil line. Neighboring plants become infected as the fungus grows plant-to-plant.

Cultural control

  • Remove infected plants and surrounding soil, taking care to include all the small, reddish-brown sclerotia, and destroy.
  • Inspect vegetative cuttings or plants of susceptible hosts imported from California or the Southeastern US for signs of infection.
  • Lime acidic soils.
  • Winter or spring crop contaminated soils to avoid exposing plants to warm soil temperatures that promote disease.

Reference Koike, S.T., Gladders, P., and Paulus, A.O. 2007. Vegetable Diseases: A Color Handbook. St. Paul. MN: APS Press.