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Fungus may affect Colorado's fall colors

Posted at 3:55 PM, Sep 17, 2015
and last updated 2015-09-17 17:55:11-04

The annual "Gold Rush" to the Colorado high country is now really getting geared up!

Plenty of aspen gold was discovered in the northern mountains in the past few days and these areas will peak in the next 7-10 days.

The central and southern areas will be about a week to 10 days later.

This year the color may not be as consistent or as long lasting as the wet weather of the early spring and summer has caused some fungus to form on the aspen leaves. It is not harmful to the tree, but it does cause the leaves to turn brown and fall more quickly.

At least two fungal diseases are to blame for the leaves now showing significant spotting or dark splotches.

Marssonina leaf spot is caused by the Marssonina fungus and is the most common leaf disease of aspen and cottonwoods in Colorado. The disease can be identified by the presence of dark brown spots or flecks on leaves, which can then fuse into large, black splotches on severely infected leaves.

Also active now, mainly on Colorado’s cottonwoods, the Septoria fungus initially causes tan spots that become irregular brown-to-black spots coalescing to cover much of the leaf by late summer.

Leaves with fungus are often smaller than normal, and fall prematurely. Infection is usually more severe on smaller trees and in the lower crowns of larger trees.

"The good news is that these diseases rarely cause any permanent tree damage or death," said  Colorado State Forest Service entomologist Dan West, in a press release. "But this is the highest level our foresters have seen in many years for some parts of the state."

Foresters have been seeing an unusually high degree of leaf blight in the mountains and along the Front Range, as far south as Aspen, the Collegiate Peaks and Colorado Springs.

The fungus conditions are intensified by abundant rainfall in the spring and summer, possibly followed by warm temperatures. A fungus epidemic can kill trees, however, the primary effect of leaf spot is generally to just make for a less spectacular viewing season.

The upcoming weekend will be dry, mostly sunny and very pleasant in terms of temperature. Highs in the mountains will be in the 60s to low 70s -- a perfect time to plan a drive to see the gilded glory of the aspens!