Caterpillars or something else?
There is a caterpillar in side those brown leafs.
Pull off and smash.
Hits mid August here, will eat leafs and twigs.
Uses the brown leafs as a shelter
Oh man, sorry to see you’re having issues.
I’ve never had that particular pest nor have I seen leaves in that condition.
Here, I just have zebra swallowtail caterpillars that can eat lots of leaves quickly, and leaf rollers, which tend to eat off the growing tips.
Also random unknown small narrow “worms” that eat leaves but not in great number.
I lost a seedling like that this year myself. Started at the top and worked downward until the tree was dead. Never saw anything on it.