Issue 2, May 6, 2013

Bright Orange Tree Bark

Last week, after several days of cool temperatures and rainy weather, I observed several trees with a bright orange color to their bark. A few homeowners, who also witnessed similar symptoms, phoned the U of I Plant Clinic with their concerns. From a distance, the trees appeared to have been used as paintball targets. Upon closer inspection, the cause appeared to be somewhat "slimy" in nature. Affected areas also appeared to be associated with sap flowing from plant injuries such as Yellow Bellied Sapsucker damage. Look for Phil Nixon's Yellow Bellied Sapsucker article in this newsletter.

Bright orange tree bark associated with Cryptococcus macerans, a basidiomycete yeast, that had colonizing sap flowing from an American hophornbean (Ostrya virginiana)

"Slimy" texture of Cryptococcus macerans that had colonized sap flowing on the bark of an American hophornmbeam (Ostrya virginiana)

Yellow Bellied Sapsucker damage (four holes near the top of the image) and bright orange tree bark associated with Cryptococcus macerans, which had colonized sap flowing from an American hophornbean (Ostrya virginiana)

Several trees species, such as maple, birch, dogwood, elm, walnut, and yellowwood, are known to "bleed" sap from wounds during spring months. The sap exuding from these bleeding trees have a high sugar content and can be colonized by many species of bacteria, yeast and fungi. Several resources, including Cornell University and University of Arkansas, have identified orange organisms similar to the one that I observed as Cryptococcus macerans, a basidiomycete yeast. The bright orange coloration results from the production and storage of carotene within the yeast cells. Under cool, wet conditions, this yeast can develop and result in a rather striking appearance on affected trees. I witnessed this orange, colonized yeast on sap occurring on Paper birch and American hophornbeam, while others have reported it to occur on Dogwoods and Muscadine grapes. The damage is mostly cosmetic and does not warrant any control measures. Wrapping the wounded areas has no benefit and is not advised. The problem should correct itself as the sap flow slows and the wounds begin to heal in the late spring to early summer. Until then, enjoy the bright colorful display nature has provided. (Travis Cleveland)

Travis Cleveland

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