Aspen trees turn my deck black!
I have about 5 quaking aspens planted around the perimeter of my deck. They're about 16 yrs old now, and this summer they started dropping some kind of sticky black substance all over my deck and the top half of lower branches. What causes this? It's never happened before (at least to this extent), but it required me to power wash the deck. Is this a normal thing for Aspens? Should I expect to see it from now on? Is there a way to make it stop?
Aphids and Scales are a common problem of many trees and shrubs, Aspen have that problem. They both produce a honeydew from the tree sap the consume. when it falls on lower leaves or any other object it readily grow a sooty mold that is black or dark grey. University of Colorado has a guide on common pests of aspen that can give you more information. Bottom line is that you need to control the aphids or scales on your trees.