Orange slime on aspen trees

Asked September 12, 2017, 2:50 PM EDT

Very recently noticed orange slime on 5 trees located in a small grove that we planted approximately 20 years ago in our yard in Snowmass. The trees are leafed out and 4 of the 5 look okay, the 5 th tree is dead. Researching the internet, I suspect it is some form of fungus, although the descriptions I read about were never on Aspen trees. I saw a number of fungicides listed, but do not know if one of these would be the best treatment, and if so, where to purchase, how to apply, etc. I will try to attach photos for your review. please advise, thank you, teresa hall

Pitkin County Colorado trees and shrubs

1 Response

Hello Teresa,

Thanks for the pictures, it makes diagnosis much easier. Unfortunately, you have cytospora, a disease that there is no treatment for. Sometimes trees with cytospora can live for awhile, it really depends on over all health. Providing adequate water and mulching around the drip line of the trees can help to relieve some of the stress they can incur when competing with grass.

The cytopsora enters the tree through wounds and any pruning should be done in the late fall or winter to avoid inoculation into new sites. It is still being determined which fungicides are effective on cytospora. It is a natural and native disease to the trees here and often found in landscape trees.

If you decide to cut down the tree that has died do so in the late fall/winter to avoid spreading spores in the yard that may infect the other trees.

If you have any other questions please let me know,