WSU Extension

Hortsense

Caption: Phytophthora root rot infecting trunk
Photo by: C.R. Foss
  
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Boxwood : Phytophthora root rot
(revision date: 4/23/2014)


Biology
Phytophthora is a fungal infection of the roots and crown. Infected plants often show wilting, discolored or dead leaves which remain on the branches, dead twigs and branches, stunting, gradual decline, and premature plant death. Infected roots become watersoaked and rot. Streaking or dark staining may be observed when cuts are made into the wood near the crown of the plant, or cankers may be present on the crown. The fungus persists in the soil and in diseased plant material. Phytophthora prefers high soil moisture.
Management Options

Non-Chemical Management
  • Plant in well-drained areas.
  • Do not overwater.
  • Do not replant boxwood in areas where it has died previously.
  • Remove and destroy infected plants, including roots where possible.
  • Plant resistant species in infected areas. Your county extension agent or WSU Master Gardeners can make recommendations.
Select non-chemical management options as your first choice!

Chemical Management


None recommended

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