[Illustration: Fruiting body of red root and butt rot of pine.]
_Polyporus tomentosus_ causes red root and butt rot of living conifers
throughout North America. Common hosts of the fungus are: spruce, larch,
pine, fir, Douglas fir, hemlock, and cedar. Throughout the southern
United States, _P. tomentosus_ has been reported in two general areas;
causing extensive degrade of mature shortleaf pine in northern Arkansas
and root and butt rot of slash pine in South Carolina, Georgia, and
Florida.
The fungus is believed to enter living hosts through basal wounds and
damaged roots. Under ideal conditions, the fungus may spread from
infected to healthy trees by way of root contacts or grafts. Growth of
the fungus is very slow, often causing host mortality 20 to 30 years
after initial infection. Wood decayed initially appears firm, but dark
reddish-brown in color. In advanced stages, the wood is flecked with
elliptical white pockets separated by brown-colored wood. Infected
conifers generally express typical root rot symptoms. Trees show
evidence of reduced radial and internodal growth, accompanied by death
of the crown from the base upward. The foliage appears off-color and
reduced in length. Under moist conditions, sporophores are produced
either at the base of infected trees or on the forest floor.
Bracket-shaped sporophores are produced at the base of infected trees
while stipitate conks are produced on the ground directly over infected
or dead roots. Fresh sporophores appear yellow-brown in color from above
with a lighter colored pore surface below.
No effective method of controlling the disease in forest stands is
presently known. However, damage and losses may be reduced by management
practices which reduce or eliminate the chance introduction of the
disease into healthy stands. In areas where red root and butt rot is
common, attempts should be made to conduct logging and thinning
operations during the dry season to avoid mechanical damage to the root
systems of the residual trees.