Importance. -- Spiculosa cankers, caused by P. spiculosus, may occur on up to 10 percent of the bottom-land red oaks in some areas. The decay column increases about 10 inches (25 cm) in length, each year.

Identifying the Fungus. -- Conks of P. spiculosus develop flat under the bark and the brown fruiting surface becomes exposed with maturity following tree death. Doubtful infections can be identified by chopping into the canker center. The brown fungus material will be exposed if the infection is well established.

Identifying the Injury (figure 50). -- Cankers appear as rough, circular swellings with depressed centers. Remains of a branch stub can usually be found in the center of the canker.

Biology. -- Spores are released from the conks and carried by the wind to branch stubs on healthy trees where infection occurs. Callus tissue is formed by the tree as a response to invasion of the cambium by the fungus.

Control. -- Cut diseased trees or deaden them to allow room for healthy growing stock. No suitable treatment is known for high-value trees in urban areas.