-- Hispidus canker, caused by I. hispidus, appears on willow
oak, Nuttall oak, white oak, and hickory. Incidence of infestation varies
by area and species, but may be as high as 13 percent. Cankers lengthen
about 6 inches (15 cm) yearly. The decay column length exceeds the canker
length. Diseased trees are quickly converted to culls.
the Fungus (figure 49a) -- Hispidus conks are about 2 to 12 inches
(5 to 30 cm) wide, spongy, stalkless, yellowish brown to red, with pores
on the lower surface. Conks are produced during the summer or fall.
They dry to a black mass, fall, and can usually be found around the
base of infected trees.
Injury (figure 49b) -- Hispidus cankers are large, elongate, sunken
in the center and bordered by callus folds. Infected stems become spindle-shaped.
A small branch stub may be found near the center of the canker where
the infection started.
-- Microscopic spores are released from conks for a few weeks. They
are spread by the wind, but most travel no more than 140 yards (128
m). Spores reaching dead branches on healthy trees start new infections.
Conks will form after deadening or felling diseased trees.
Cut hispidus-diseased trees as soon as possible for salvage and to reduce
disease spread by limiting spore dissemination to healthy trees. No
suitable treatment is known for high-value trees in urban areas.