WSU Extension


Lettuce : Bottom rot
(revision date: 6/3/2014)

Bottom rot of lettuce is caused by a soil-borne fungus that is common in wet soils. Head lettuces, particularly the 'Big Boston' types, are attacked as they near maturity. The stems and midribs of lower leaves develop sunken, brown, necrotic spots which may enlarge to involve the entire stem or midrib. The surface of the spots may show a brown exudate or may be covered with a white to brown growth of the fungus. Brown or gray-brown fruiting bodies of the fungus can also be present in the lesions. Infected heads become slimy and later dry into a blackened mummy. Bacterial rots often attack lettuce after infection by bottom rot. The fungus causing bottom rot of lettuce also commonly causes damping-off of seedlings and seed rots in many species of plants.
Management Options

Non-Chemical Management
  • Rotate crops. Do not plant lettuce in the same location each year.
  • Plant non-susceptible crops such as sweet corn and onions in infected areas.
  • Plant in well-drained soils or raised beds.
  • Space plantings to provide good air circulation.
  • Do not overwater.
Select non-chemical management options as your first choice!

Chemical Management

None recommended

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Caption: Lettuce bottom rot
Photo by: R.S. Byther
Caption: Lettuce bottom rot
Photo by: R.S. Byther