WSU Extension


Caption: Armillaria root rot infecting trunk
Photo by: C.R. Foss
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Plum, Prune (Fresh) : Armillaria root rot
(revision date: 5/20/2014)

Armillaria root rot is a fungal disease often found in newly cleared soils or soils which have been flooded. Aboveground symptoms typically include production of smaller-than-normal leaves, leaf yellowing, premature leaf drop, and branch dieback, often on only a portion of the tree. The fungus may be found as white, felt-like masses beneath the bark at the crown, as honey-colored mushrooms at the base of infected trees in the fall, and/or as shoestring-like rhizomorphs, which are dark strands of the fungus growing on or just beneath the soil surface. Infected trees may also exhibit a dark black line in the infected area encircling the base of the plant. Trees damaged by human activity such as construction or improper irrigation are more susceptible.
Management Options

Non-Chemical Management
  • Use resistant rootstocks. Marianna 2624 rootstocks are reported to be resistant.
  • Provide proper culture. Healthy plants are more resistant to disease.
  • Remove damaged trees if necessary. When possible, remove roots 1" or more in diameter and air-dry soil before replanting.
  • Avoid injury to roots and trunk.
  • Replant with resistant species in infected areas. Lists are available in the PNW Plant Disease Management Handbook and the Sunset Western Garden Book, or contact your county Extension agent or WSU Master Gardeners.
Select non-chemical management options as your first choice!

Chemical Management

None recommended

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Caption: Armillaria root rot infecting trunk
Photo by: C.R. Foss
Caption: Armillaria root rot infecting trunk
Photo by: R.S. Byther
Caption: Armillaria rhizomorphs
Photo by: R.S. Byther