Phytophthora Root Rot

Blueberries November 17, 2011 Print Friendly and PDF


Phytophthora root rot may occur in
poorly drained fields such
as the one seen here.
Photo by David Ingram, MSU Cooperative Extension Service.


Phytophthora root rot (Phytophthora cinnamomi) may occur at poorly drained sites or in low areas of fields.

Symptoms include:

  • Early above-ground symptoms include:
    • Leaves turn yellow.
    • Leaf margins burn.
    • No new leaf growth
  • As disease progresses:
    • Terminal leaves become small
    • Excessive defoliation occurs because of severely damaged roots.
    • Stunted and wilt-prone leaves.
    • Restricted root system that allows plants to be easily rocked back and forth, or pulled up.
    • Dead or prematurely defoliating bushes.
    • Defoliation and poor growth follow the contours of the low areas where excessive moisture is present.

Disease Cycle includes:

  • Zoospores (swimming spores) produced by the fungus infect blueberry roots.
  • Roots collapse and decay.
  • Defoliation and poor growth follow the contours of the low areas where excessive soil moisture is present.
  • Abundant soil moisture and temperatures between 68 F and 90 F (20 C to 32 C) promote disease development.

Control Measures include:

  • Having adequate ditches.
  • Planting on raised single-bedded rows.
  • Taper-disking or sweep-blading.
  • Using "sock pipe" and other types of pipe normally used for residential septic fields for draining small areas.
  • Incorporating peat or bark mulch and, then, planting shallow and using additional mulch to form beds if planting on wet clay or clay loam soils.


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This work is supported by the USDA National Institute of Food and Agriculture, New Technologies for Ag Extension project.