CPPgardener said: to the forum Ryan!
The tree looks very healthy overall so don't panic just yet. The spots look like maybe some kind of small insect like aphids or thrips might have fed there at some point in the past. Unless you see some small insects on the newer leaves I wouldn't worry about it, they've probably come and gone already. Check on the bottom of the leaves and see if something is hiding there to be sure you're not missing them.
The older inner leaves have lived out their usefulness to the tree and it is dropping them— nothing to worry about either.
If anything new happens, post again so we can fine tune the diagnosis.
As for fertilizer burn, that would depend on what and how much you used. If you followed the directions carefully there should be no problem.
Thank you for your assistance here. I very much appreciate it.
I went out to check on the tree a couple more times, and I did notice some development, though perhaps it is all normal: Both the spotting and leaf dropping picked up quite a bit in just a week. The spots look bigger and more numerous, and there are many more leaves dropping--not just old ones, but many are newer leaves, created in the last couple months--not the very newest growth, mind you. I show updated pictures here, just in case. Some of the leaves are also browning from the side in a semi-circular pattern, as one of the pictures shows. Maybe that's the same as them browning from the tip, but I thought it relevant.
I am not alarmed... yet.
I am just trying to learn about these Shamel Ash trees. This is the first time I had an ash tree, and so all these characteristics are foreign to me. I am familiar with leaf dropping, but I thought it was mostly in the winter with this variety, and since there are about 50 brown, dried leaves on the ground at this point, many of them newer ones, I thought I would nip it in the bud if it was something solvable. I water once every 3 days at this point in the year, for about 120 minutes on a drip system. It is about 50 gallons each time.
Moving on, the spots are just confusing to me, and since there are more of them that are much more obvious, I thought it might be something ongoing. I didn't see anything alive under the leaves last week or today, but I did find this powdery, soft material under some of the leaves, as seen in the last picture. It wipes right off, almost no weight to it. I also saw several leaves that had that same white stuff, but a very small amount, and attached to a white thread (same material) on the underside of the leaves. Otherwise, no bugs down there. But the spots are now much bigger. Maybe it is just residual from something months ago, but the undersides of the leaves show no evidence of bites, unless they are very small.
Thanks again for the assistance.