Irpex canker, caused by _Irpex mollis_, is prevalent in bottomlands and
on upland areas of the Southeast. In the bottoms, Nuttall, water, and
willow oaks are affected. White, chestnut, southern red, and black oaks
are the hosts of this disease on upland sites.
[Illustration: Fruiting body of Irpex rot.]
[Illustration: Cross section of tree showing rot and decay.]
Irpex canker is also considered to be a canker-rot disease. Symptoms on
infected trees frequently involve irregular cankers up to two feet in
length. Cankers are usually found on trees eight to ten inches in
diameter or larger, at a height of twenty feet above the ground. Branch
stubs, signifying probable infection points, are usually present in the
centers of cankers. The portion of the trunk affected is usually swollen
but sometimes may be sunken. At the base of the sunken portion of the
canker are small, creamy-white, toothed fruiting bodies or conks with a
leathery texture. Conks also appear on hardwood logs. The wood behind
cankers is characterized by a tough, spongy, white rot which extends as
much as eight feet above and below the canker. The decay pattern may
also extend downward into the roots. In cross-section, the rotted areas
appear as finger-like projections radiating out toward the sapwood.
Gradually the rot column tapers to a thin central core beyond which
white flecks appear, and this early rot stage is concentrated along the
rays of the oaks.
Control for Irpex canker is the same as for other canker-rots—salvage of
undesirable cankered trees.