Armillaria Root Disease

1
Armillaria Root Disease

• Noah Barstatis
• April 19, 2005

2
definition

• root rot/fungus
• root rot, shoestring root rot, honey mushroom
• over 30 known species
• infects many different tree species
• similar host affects
• Armillaria ostoyae
• very common and aggressive root rot pathogen of
  conifers

3
identification

• resin flow from tree base
• crown thinning or changing color to yellow or red
• distress crop of cones
• white mycelial fan under bark (at tree base)
• black rhizomorphs penetrating root surfaces
• honey colored mushrooms near base of tree in fall
• can affect single trees or patches (depending
  on geographical area)

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b)
a)
c)
d)
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disease cycle

• root rot infects roots and bole
• highly pathogenic
• airborne spores unimportant for spread
• rhizomorphs most common pathway of spread and
  infection
• young trees are quickly killed, while older trees
  may be able to survive for many years

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predisposing agent

• STRESS
• insufficient water, light, or soil nutrient
  availability, temperature extremes, pollution,
  insect attack, partial cutting, wildfire damage,
  and other diseases
• Armillaria frequently occurs with other root
  diseases, such as Annosus, and is itself a
  predisposing factor for bark beetle attack.

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management strategies

• chemical treatments
• not cost effective
• replanting disease tolerant site-suited trees
• most frequent in pacific NW states
• remove diseased stumps and trees from site
• too expensive for large areas

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management strategies (cont.)

• selective harvesting of root-disease infected
  trees may aid the infection
• leaves behind a fresh supply of infected stumps

9
management tools

• Root Disease Analyzer Armillaria Response Tool
  (ART)
• a web-based tool that estimates Armillaria root
  disease risk in western US forests
• model build by Forest Service RMRS
• looks at habitat types and estimates risk value
• indicates how some fire planning/fuel management
  activities may aid the spread of Armillaria

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negative impacts

• outright mortality of trees
• timber stands
• recreation areas
• orchards
• increased fuel component
• standing dead
• ladder fuels
• downed material

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positive impacts?

• important to ecosystem processes
• creates gaps in canopy
• increased understory production
• creates snags and downed logs
• wildlife habitat
• improves resources
• nutrient cycling and increased site productivity

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wildfire

• increase of risk
• build-up of dead standing and downed material
• depends on infection size and homogeneity
• higher mortality rates post fire
• trees stressed from infection are more likely to
  be killed with additional stress from fire

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prescribed fire

• increases nutrient availability
• pulse of nutrient flow following fire
• again, added stress
• scorched needles and bole
• no documented effect on the underground fungus

14
Arizona

• Armillaria is not prevalent in Arizona ponderosa
  pine forests
• small patches exist on the north Kaibab National
  Forest
• root disease is more common in the mesophytic
  than xerophytic ponderosa pine zone

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Humongous Fungus

• as large as 1,665 football fields combined
• 3.4 square miles in size
• covers 2,200 acres of land
• calculated to be over 2,400 yrs old
• Blue Mountains Eastern Oregon
• www.fs.fed.us/newcentury/fungus.htm

16
citations

• Armillaria root disease. Forest Pathology.
  http//www.forestpathology.org/dis_arm.html
• Forest health notes Annosus root disease.
  Wisconsin State University. http//ext.nrs.wsu.edu
  /forestryext/foresthealth/notes/annosusrootdisease
  .htm
• Forest health notes Armillaria root rot,
  shoestring root rot, honey mushroom. Wisconsin
  State University. http//ext.nrs.wsu.edu/forestrye
  xt/foresthealth/notes/annosusrootdisease.htm
• Lundquist, John. 2000. A method of estimating
  direct and indirect effects of Armillaria root
  disease and other small-scale forest disturbance
  on canopy gap size. Forest Science. 46(3)
  356-362.
• Miller R.M. and Dodge D.J. 1997. Fungal response
  to disturbance agriculture and forestry. The
  Mycota IV environmental and microbial
  relationships. Berlin Springer-Verlag. p. 65-84.
  
• Moir, William H., B. Geils, M.A. Benoit, and D.
  Scurlock. 1997. Ecology of Southwestern Ponderosa
  Pine Forests. Pages 3-27 in Block, William M. and
  D.M. Finch, tech. ed. Songbird ecology in
  southwestern ponderosa pine forests a literature
  review. Gen. Tech. Rep. RM-GTR-292. Fort Collins,
  CO U.S. Dept. of Agriculture, Forest Service,
  Rocky Mountain Forest and Range Experiment
  Station. 152 p.
• Williams, R.E., C.G. Shaw, III, P.M. Wargo, and
  W.H. Sites. 1989. Armillaria root disease. Forest
  Insect and Disease Leaflet 78. USDA Forest
  Service.
• McDonald et al. 2005. Fuel planning science,
  synthesis and integration. RMRS-RN-23-13-WWW. Ft.
  Collins, CO. U.S. Dept. of Agriculture, Forest
  Service, Rocky Mountain Research Station. P.2