Q. coccinea, being native to dry, upland soils, shouldn't be bothered much by a 2 month dry spell (did you have a ridiculously wet spring over there in MO?) as far as I know.

I don't think the leaf issue has anything to do with that except as being favorable to the pest itself, perhaps.

Been seeing allot of this kind of damage and not just on oaks. I've assumed it was some insect, but have not tried to find the culprit as the damage has not been extensive enough to cause concern. But I haven't noticed damage like this in years past. Perhaps related, I have seen allot of damage to our crabapples and serviceberry that appears to be grasshopper, but again I have not definitively ID'ed the culprit.

These two things taken together, makes me wonder that with the exceptional droughts locally the last two years, if the populations of pests crashed due to a lack of healthy hosts, resulting in a crash in the population of predators. This year having been much better, the damaging pest population would likely rebound much more quickly than their predators, resulting to more damage to the plant hosts. I don't "KNOW" that this has happened, but it does fit the observations locally.

So I don't have a name for you, or a pest, just a hypothesis. If it returns next year, I will be more concerned.

Arktrees

The walnuts & mulberries (blech) are almost bare due to the fall webworm this year - the nettings in the branches are so bad you can see them from a half mile away in some areas.

The oaks are mildly affected by some "oakworm" as my wife IDed it as well, but not to the point of defoliation. I found a few squashed caterpillars plus little green poop dots all over the sidewalk under a large Willow Oak along our street the other day. The tree only has some scattered leaf damage though, nothing bad.

Oaks have a plethora of pests (and their predators). Almost every oak-leaf on my lot has some damage, but the total photosynthetic area of the trees are not actually much affected. Watch an oak branch (especially on new sprouts) closely and you'll see a haze of tiny flying bugs -- often tiny parasitic wasps dining on the leaf-eaters.

Amazing the live so long. MOBOT lists a page of various oak problems.

I will not pqnic or do anything rash unless it gets an early and severe start next year. Leaves are due to fall off, or at least turn, next month anyways.

I swear I saw that before or maybe one of the neighbors has a similar problem and asked me.

See it often here, too. I think it is insect damage and NBD unless it happens to the majority of the canopy. Just unsightly.

I agree that doing nothing is the best course of action if that helps any.

Locally, certain species of the red oak group get hit hard every year by insects with rubra being their favorite (sometimes 50% defoliated). OTOH, they seem to leave texana, falcata, and phellos pretty much alone with just slight damage on coccinea.

Albas seem less affected overall around here, too. The white oak group in general, actually.

However it seems anthracnose is a bit MORE of a problem for the albas.

My 1 year in ground Scarlet oak looks worst for wear too, for whatever reason. I have a couple other oaks that are leaf-bare because of some catipillar like vultures, but they will be leaf-less soon, so I am not worried, but, I will be sprinkling some BT to kill off future wormies. One of my 3 Q. Robur is pretty bare on top from some catipillar-like wormies now.

I find these on my red and white oaks every year which end up with the leaves looking similar. Not much of a concern since I only notice a few leaves when looking for caterpillars.

Here is a link that might be useful: pear slugs

I did some pruning today and there was a web of dead leaves (tan) on my Swamp White oaks 4 of them. Also the Quercus Robur 1 out of 3 of them had the top leaves eaten. The buds for next year on the tree look fine, so no biggie. As you mentioned Scarlet oak, mine is ugly leaved. My Live oaks 2 of them have white covered, sooty mold on some leaves. Anyhoo, I will worry if they are ugly leaved next spring, after the new leaves come along.