Thanks for contacting us about the black stuff on and under your aspen tree. This sounds like sooty mold. It is a secondary problem that occurs when there are large populations of aphids or scale on a tree. These insects excrete honeydew and the mold grows on the honeydew. The mold can be hosed off. The larger issue is what insect has infected your tree. Three links are included below for you to read, and see if you can identify the insect. Aphids will be on the leaves and new twigs, and scale will be on the bark of branches and/or the trunk. Scale has a tiny, hard, dome-shaped shell that covers the insect itself.

Look at the pictures of the insects in the fact sheets below, see if you can see them on your tree. If you can identify the insect, how to manage it is also included in that same fact sheet.

• Tree covered in soot: https://hortnews.extension.iastate.edu/2007/9-12/SootyMold.html

• Aphids on shade trees: http://static.colostate.edu/client-files/csfs/pdfs/aphids.pdf

• Oystershell scale: http://extension.colostate.edu/docs/pubs/insect/05513.pdf

If these don’t resolve the issue, please respond. Include pictures of the whole tree and area, as well as up-close pictures of what you might find on the tree trunk, branches or leaves.

The spots on your leaves are probably a common fungus, marssonina. Aspen are particularly susceptible along the Front Range; they have fewer problems when they live at their native higher altitude. One of the best ways to manage that is with good sanitation in the fall; throw the leaves in the trash so the fungus does not overwinter and start up again the next year. More information on that: http://extension.colostate.edu/docs/pubs/garden/02920.pdf

Karin

Gina, the leaves have aphids. They will produce the honeydew, which produces the mold. I can't tell from the pictures whether or not scale is also present on the bark. The links I sent earlier will help you resolve both issues.

Karin