Good afternoon Larry,

We received your pictures and questions about the leaf curl on your trees. This is a common occurrence of Herbicide Damage. The damage could occur when the herbicide is misapplied or applied under improper conditions. Avoid misapplications by applying sprays only at non-windy times to avoid damage from drift.

The following link provides a document about herbicide use around trees. It provides information about herbicide damage as well as alternate methods of weed/grass control around trees:
https://cmg.extension.colostate.edu/Gardennotes/656.pdf

The damage to your tree is mostly cosmetic and the tree should recover next year provided the tree does not continue to be exposed to the herbicide.

I hope this information is helpful. Feel free to contact us if you have addition questions.

Linda, Weld County Colorado Master Gardener