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Armillaria Root Disease - Armillaria
spp.
   USDA Forest Service - Missoula Archives James W. Byler, USDA Forest Service USDA Forest Service - Missoula Archives www.ipmimages.org www.ipmimages.org www.ipmimages.org  HOSTS: Grand and Douglas Fir under the
age of 30 years primarily, but also occurring in many other conifers
and hardwoods. DESCRIPTION:
White
mycelial (fungus) fans are present in the cambium and bark of roots and
stems. Honey colored mushrooms (the fruiting bodies) may be found at
the base of trees during wet periods in the fall. Some conifers (e.g.
Douglas fir) produce resin at the tree base when attacked by Armillaria.
Resin becomes evident when the fungus has moved up the roots to the
root collar. Decayed wood initially is gray to brown-stained and
appears water soaked. As the disease advances, the decay is white to
yellow in color and is stringy or spongy. LIFE
CYCLE: The
disease spreads from a host tree or stump to uninfected live trees in
two ways: root systems of the two trees come in contact and knit
together, or fungal mycelium grow through the soil from infected to
susceptible tree roots. The fungus spreads along the root system of the
tree penetrating its bark and entering the cambium. It then continues
to spread along the root until it reaches the root collar where it
spreads to other primary roots. Death occurs when the tree is girdled
at the root collar, when bark beetles attack, or windthrow occurs. Armillaria
survives as a saprophyte on dead roots and stumps for 20-30 years.
Contact with old roots can infect new trees. CONTROLS:
Remove
diseased tree stumps, roots and all. |
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