Armillaria Root Rot of Blueberry

Blueberries November 17, 2011 Print Friendly and PDF

 

Armillaria Root Rot
A plant infected with Armillaria Root Rot.
Photo courtesy of NCSU Cooperative Extension Service.


Armillaria root rot (Armillaria mellea, A. ostoyae) is a rare disease of blueberries in the United States, but it can cause serious damage where it occurs.

Symptoms of Armillaria Root Rot of Blueberry include white mycelial fans present between the bark and the hardwood at or slightly below the soil line.

Other symptoms include:

  • Infected plants are low in vigor and may appear to suffer from a nutrient deficiency.
  • Leaves are small and cholortic.
  • Branches wilt suddenly.
  • Plants decline over several years or die within a short time.
  • Black shoestring-like strands (rhizomorphs) may be attached to the roots or trunk or growing freely in the soil.
  • Yellowish brown mushrooms (honey mushrooms) are sometimes produced in clumps at the base of the bush.


The Disease Cycle for Armillaria Root Rot of Blueberry includes:

  • Most likely occurring on a sandy, well-drained site where an oak forest was cleared.
  • Surviving as mycelium and rhizomorphs on old roots and stumps.
  • Spreading between bushes by root-to-root contact.
  • Surviving on wood chip mulches.
  • Spores disseminated from the mushrooms probably are not important in spread.


Control Measures for Armillaria Root Rot of Blueberry include:

  • Disking the soil thoroughly, especially if a forest (particularly oak) was present at the site, and remove as many roots as possible.
  • Leaving the area fallow for at least three years.
  • Fumigating the soil before planting (however, fumigants do not penetrate deeper than 50 cm).
  • Removing and burning infected bushes.
  • Removing wood chip mulch from bushes surrounding an infected bush.


References:

  • Caruso, F.L. 1995. Armillaria root rot. Compendium of Blueberry and Cranberry Diseases. pp. 22-23. F.L. Caruso and D.C. Ramsdell, eds. APS Press, St. Paul, MN. 87 pp.
  • Cline, Bill and Annemiek Schilder. 2009. Michigan Blueberry Facts: Armillaria Root Rot. Retrieved from http://www.blueberries.msu.edu/armillaria.htm. Retrieved 03 March 2010.[[category:

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