Cytospora Canker
Cytospora chrysosperma

Photos and Narrative by Curtis E. Swift, Ph.D.
Colorado State University Extension
Tri River Area

Orange-stained bark and sap flow are indicative of early cytospora canker infection

Cytospora canker caused by the fungus pathogen Cytospora chrysosperma (Valsa chrysosperma) is common on many deciduous trees and shrubs to include willow, aspen, cottonwood, poplar, and maple. The orange bark discoloration and amber-colored ooze is typical on aspen. As infected tissue dies, pimple-like fruiting bodies called pycnidia form . This give the dead bark a rough texture as is seen in these two photographs. Under moist conditions small orange tendrils of a jellylike material oozes from the pycnidia.

Cytospora is typically considered a problem with plants that are under stress with the fungal pathogen gaining entry through dead wood and wounds to include cat scratches, lawn mower and weed whip damage, and winter injury such as sunscald. Pruning wounds are equally susceptible to infection. Healthy, vigorous trees and shrubs seldom contract Cytospora canker.

A related fungus causes a gumming of peach trees and other stone fruits and has been called "Gummosis" by the commercial peach growers in Western Colorado for decades. Leucostoma persoonii is the causal agent of this disease problem.

Further Information on Cytospora Canker caused by Cytospora chrysosperma is available through Colorado State University's On-Line Publication Site.

Placed on the Internet April 15, 1996
Updated June 18, 2009