Deb Babcock: Aspen decline truly SAD
March 1, 2010
■ For maps and additional information about sudden aspen decline, or SAD, visit here
Steamboat Springs — The acronym for a condition affecting local aspen trees is so apt for what probably is the most popular of all the deciduous, or leaf-bearing, plants of the Rocky Mountain West.
Sudden aspen decline, or SAD, is a phenomenon that already has affected more than 17 percent of the aspen trees in Colorado, where entire stands of aspens with SAD have died seemingly overnight. It is particularly evident in the northwestern and southwestern parts of our state, where dead trees left huge brown holes in our usual golden display of turning leaves in the autumn.
Foresters attribute the cause of SAD to several factors, but primarily to the warm, dry summers of 2000-05 and the subsequent pests that came in to feed on old, weakened stands of trees and the diseases that followed. It seems to affect mainly overstory trees, those with a trunk diameter of 5 inches at breast height, or 4.5 feet. And it seems to mostly affect trees at the lower elevations that face west or south. Smaller trees do not seem to be affected.
There doesn't appear to be much that can be done to stop the dieback, but foresters are trying to cut or burn some of the affected stands before the root system deteriorates to the point that the clone cannot regenerate more sprouts.
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Generally, when a healthy stand of aspens starts to age and die, the root system sends up lots of new shoots, or suckers, which help regenerate the stand. Unfortunately, aspen stands affected by SAD seem unable to produce many healthy new shoots. Fortunately, at least in Routt County as opposed to other sites in western Colorado, the stands seem to be rejuvenating naturally. You can see it in the aspen stands up the Elk River corridor.
Scientists first started noticing the bare branches of SAD-affected trees in 2004. As they studied them further, they noted the pests such as two aspen bark beetle species and two poplar borer species in greater numbers than expected or seen before.
As a homeowner with aspen trees in your landscape, the chances of SAD affecting your trees should be small if you have cared for them properly, especially by providing water when it is needed. However, if you find your aspens exhibiting signs of distress, there are some steps you can take to address the problems. For help, contact the Routt County Cooperative Extension Office or visit http://www.colostate.edu on the Web, and type "aspens" in the search engine.
Deb Babcock is a master gardener through the Routt County Cooperative Extension Office. Call 970-879-0825 with questions.