Aspen Tree leaves turning yellow and some turning black
We have two aspen trees where the leaves have turned yellow and now the leaves are turning black at the very top of the trees and this is working it's way down the tree starting at the ends of the tree limbs. Can you tell me what is going on with these trees and if anything can be done to help them?
Larimer County Colorado
There are, unfortunately, multiple problems that affect aspen in home landscapes. This is a tree that really prefers higher elevations and native soils. We do have a fact sheet on the various aspen leaf spots and diseases: https://extension.colostate.edu/topic-areas/yard-garden/aspen-and-poplar-leaf-spots-2-920/
Without a photograph or more information, it's difficult to diagnose which disease it is. However, it's too late to treat or do anything. Most of these diseases are fungal and need to be prevented before they happen. At this point in the season, the leaves are likely to fall off early. When this happens, be sure to rake them up and throw them in the trash, in an attempt to break the cycle.
If the tree does lose limbs or has dieback, then you can prune those out next winter/early spring.
Thank you for your response. It was kind of what I suspected, from what I had read on your web site, but with more useful info. If this fungus gets into the soil, does it linger for years or does it only last for a season. I've always raked the leaves up or sucked them up with my mower with the catch bag, but don't know how they were handled before we bought our home.
At what point in the spring should fungicide be applied to the tree?
Fungicides can be applied, if you're wanting to go that route. You can find an arborist by visiting www.treesaregood.com
No, the fungus doesn't last for years in the soil, but the spores will always be present in the environment. This is a perennial problem with aspen.