Good Evening Tom, 

Thank you for contacting the U of M Extension Service. 

I cannot determine from your photos, but it appears to be an insect eating the new leaves. 

I cannot tell what type of insect this is from the photo. Here is a link to the What's Wrong With my Plant? from the U of M Extension Yard and Garden website: https://apps.extension.umn.edu/garden/diagnose/plant/deciduous/poplar/

Hopefully you can work through the above information to find what you need. 

This information describes various problems with poplar (aspen) trees. If you don't find the answer there, please send a description of the critter, or a closer up photo. Are the trees being defoliated? 

Your photo # 5 appears to have leaves that are curled at the ends. You indicated this tree was in a far corner. It almost appears to be chemical burns on the leaves or chemical drift. 

Is photo # 1 include a caterpillar? Or is this part of the branch? 

Here is another link to the U of M Extension website about tree care: https://extension.umn.edu/forestry/tree-selection-and-care. 2022 was a drought year. Drought stressed trees are more susceptible to pests and disease. Your trees may be stressed from the drought. 

Good Luck!