DENVER (CBS4)– This year’s drive through the mountains to view the fall colors could be less vibrant this year thanks to a fungus that is growing on most of the leaves.

The Colorado State Forest Service says some aspen and cottonwood trees in northern Colorado and along the Front Range are infected with illnesses that cause dark splotches and spotting on their leaves, creating less vibrant colors and early leaf loss.

The fungus is visible from Fort Collins to Colorado Springs and all the way west toward Vail, as far south as Aspen and as far north as Steamboat.

A fungus has spread among aspen and cottonwood trees (credit: CBS)

A fungus has spread among aspen and cottonwood trees (credit: CBS)

“The leaves that we’re seeing that have these dark, dead spots in them are the leaves that are impacted. There are two different pathogens on this particular leaf, there is one pathogen that’s creating this dead area and then the other pathogens that are all around the leaf,” said Colorado State Forest Service spokesman Dan West.


The unusually wet spring helped spread the common leaf fungi marssonina and septoria. In order to help stop the spread of disease homeowners are encouraged to rake up and dispose of infected leaves and twigs.

Officials say the trees may look bad, but there should be no permanent damage and they will regrow healthy leaves next year.

Despite the fungus, there are still many areas to view bright fall colors once the foliage reaches its peak.

“Many of the other trees like the maples and the oaks are not impacted at all,” said West.


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