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Caption: Phytophthora root rot on raspberry
Photo by: R.S. Byther
  
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Raspberry : Phytophthora root rot
(revision date: 5/6/2014)


Biology
Phytophthora root rot can be a problem in the Pacific Northwest when raspberries are planted in areas with poor drainage. The fungus attacks the fine roots, which rot and die. Infected root tissue is cinnamon brown in color instead of a healthy white color. Rotten roots are unable to absorb sufficient water and nutrients, so canes wilt and leaves become withered and scorched during warm weather. Fruiting canes are usually shortened and may die prematurely with fruit failing to form or withering before maturity. The fungus produces overwintering spores that can survive for years in infected plant debris and soil.
Management Options

Non-Chemical Management
  • Completely remove and dispose of affected plants. Sterilize tools after use. Do not move affected plants or soil to unaffected areas.
  • Improve soil drainage by planting raspberries in raised beds (soil level at least 12 inches above the surrounding soil.)
  • Plant resistant cultivars if available. 'Chilliwack', 'Meeker' (mature), 'Newburgh', 'Sumner', and 'Summit' are somewhat resistant. Your county extension agent or WSU Master Gardeners can make recommendations.
  • Prevent disease by planting only disease-free materials in fertile well-drained soils. Do not plant in waterlogged, poorly drained, or frequently flooded areas. Do not overwater raspberries.
Select non-chemical management options as your first choice!

Chemical Management


None recommended

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Caption: Phytophthora root rot on raspberry
Photo by: R.S. Byther
Caption: Phytophthora root rot on raspberry: diseased vs. healthy roots
Photo by: R.S. Byther
Caption: Phytophthora root rot
Photo by: R.S. Byther