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Caption: Phytophthora collar rot on madrone
Photo by: R.S. Byther
  
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Madrone : Collar rot (Phytophthora)
(revision date: 4/28/2014)


Biology
Collar rot is caused by a fungus which lives in soil. Leaves of infected trees may be discolored, stunted or may die. Cankers occur near the trunk base, and appear sunken, brown or black, and water soaked. Margins of the cankers are definite and may exude a dark fluid. Dogwood, maple, and other trees also contract collar rot.
Management Options

Non-Chemical Management
  • Avoid wounding trees and cover any wounds with dressing.
  • Small cankers may be removed successfully if all discolored bark and wood plus a 1-inch buffer area of healthy tissue are removed and destroyed. Wash and sterilize tools.
  • Plant only in well drained areas, or correct drainage.
  • Do not allow overhead irrigation water to run on trunks or collect at the base of madrones.
Select non-chemical management options as your first choice!

Chemical Management


None recommended

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Caption: Phytophthora collar rot on madrone
Photo by: R.S. Byther