Aspen leaves can curl for a variety of reasons, often related to pests or diseases. According to information from educational sites:

Aphids are common pests that can cause aspen leaves to curl. They feed on the sap of the developing leaves, which can result in the leaves curling and the presence of a sticky substance called honeydew on the leaves.

Marssonina Blight, also known as ink spot disease, can affect aspens, leading to leaf spots and potentially curled leaves.

Aspen Leaf Miners and Sawflies are other insects that can damage aspen leaves, causing them to curl or show other signs of distress.

Fungal diseases like Black Canker and Sooty Bark Canker can also cause leaf curling as they affect the tree. More information at these links:

aspen-b-and-b-spring-2021-web.pdf (uwyo.edu)

Common Insects & Diseases of Aspen | Colorado State Forest Service | Colorado State University (colostate.edu)

To maintain the health of your aspen trees and prevent leaf curling, it’s important to:

Maintain a proper watering schedule, as aspens can suffer if over- or under-watered.

Avoid direct sprinkling of leaves by lawn watering systems.

Prevent wounding the main trunk with mowers or weed wackers.

Trim out cankers if they are less than half the circumference of the aspen.

Clean up heavy scale-insect infestations.

If you’re dealing with curled leaves, it might be helpful to use systemic insecticides, particularly if aphids have caused the curling. Contact insecticides and soaps can also be useful when aphids are exposed on leaves.

It’s always a good idea to get a professional diagnosis, just to make sure there are no other problems.  Because of the many problems associated with leaf curling, I recommend one of the below options:

OPTION 1:

For a confirmed and precise identification of the problem, I recommend you send all your images by e-mail to the MSU Plant & Pest Diagnostics Lab. The experts there can also provide you with the best treatment options. Their email is <personal data hidden> - Please include your name – The lab will let you know if they need a sample sent. FYI – The lab may also ask for additional images too.

Their website is at this link:

Plant & Pest Diagnostics (msu.edu)

Their Contact Information is at this link:

Contact Us - Plant & Pest Diagnostics (msu.edu)

This link will explain the details on submitting a sample to MSU Plant & Pest Diagnostics Lab:

Submit Samples - Plant & Pest Diagnostics (msu.edu)

OPTION 2:

You can consult with a local arborist for a more detailed onsite assessment and personalized advice. To find an arborist in your Zip Code go to this link:

Find an Arborist (treesaregood.org)

I hope this helps!