Stem Decays and Stains
FIELD GUIDE TO INSECTS AND DISEASES OF ARIZONA AND NEW MEXICO FORESTS

Canker Rot of Oak
Inonotus andersonii (Ellis & Everh.) Cerny

Hosts: Oaks

Figure 208. Inonotus andersonii forms bright orange fruiting structures beneath the bark of infected trees that blacken with age. Symptoms/Signs: I. andersonii produces flat, bright yellow to yellow-brown fruiting bodies with peg-like outgrowths beneath the bark or outermost layers of wood. These fruiting bodies degrade quickly, turning dark dull brown to black, as if the wood was burned.
Biology: Branch stubs are the most common sites of infection, but entry also occurs through trunk injuries. I. andersonii first invades heartwood causing a white rot, and then moves outward, killing the sapwood and cambium (hence the name, canker rot). Trees often break at these cankers.

Effects: I. andersonii is a common decay pathogen of oaks throughout the United States, but also causes mortality where decay continues out into the cambium, girdling infected trees.

Similar Insects and Diseases: Old fruiting bodies of I. andersonii are black and are often mistaken for fire scars.

References: 29, 92