WSU Extension

Hortsense

Caption: Phytophthora root rot infecting trunk
Photo by: R.S. Byther
  
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Pine : Phytophthora root rot
(revision date: 4/23/2014)


Biology
Phytophthora root rot is usually a problem only in areas with poor drainage or where flooding occurs. The fungus attacks the roots, which rot and die. The infection moves up into the crown, where the cambium (soft inner bark) turns reddish-brown instead of the normal greenish-white. Older trees may develop cankers on the trunk, possibly accompanied by split bark and oozing pitch. Lower branches wilt, turn brown, and die back. Younger trees are often killed outright, while infected mature trees may show wilting, branch dieback, or other signs of inhibited water and nutrient uptake. Phytophthora root rot on pines is mainly a problem in nurseries or other irrigated plantings.
Management Options

Non-Chemical Management
  • Prevent disease by planting only disease-free materials in noncontaminated soil.
  • Improve soil drainage by incorporating organic material or using raised beds.
  • Avoid soil compaction, which reduces drainage. Construction, heavy foot traffic, or machinery can cause soil compaction.
  • Remove and destroy all infected plants and plant debris.
  • Plant resistant species in infected areas. Pinus mugo var. mughus has been found resistant to Phytophthora cinnamomi and P. lateralis. Your county Extension agent or WSU Master Gardeners can provide additional information found in the PNW Disease Management Handbook.
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: R.S. Byther