I thought I would get some bites:) Pun intended. It was ants. I suspect it was near there nest - I have had this happen, not often but occasionally. I caught them quickly and it is doing better.

We have leafcutter ants here in Texas, but I don't think there are any up north. This sounds odd. Are there other ants that harm leaves? At least the top leaf doesn't look like it has even been cut.

Looks like the leaves were stressed/burned with something as they emerged. Not sure they would turn yellow quickly like that from ant bites unless they have toxins. You saw the ants on the seedling? I always wonder if you are burning young sensitive plants with something.

You seem to plant hot weather seeds early in ground, which can result in sickly seedlings prone to problems. You could start some seeds in pots then transplant or wait until it is hot if you have problems. You could improve the soil in spots where you put seeds.

Unless you have rare seeds, plant multiple seeds then keep the best seedling.

I saw them devoring it and I have seen it before. It is "normal" tiny ants. If you doubt they do it look at any ant nest you have ever seen - no vegetation. They kill it. They klike this location, I had the same thing happen last year. Literlly 2" away is one they had not hit yet that is fine. I caught them within hours of starting. Seedling was fine at sunrise and at noon covered in ants tearing it apart. I used sevin, all ants died, damage stopped and plant is recovering.

No question it was ants.

I use Terro liquid ant poison (5% boric acid) to eliminate ant colonies. Just squirt a small amount into a soda pop/beer bottle cap and place it near their nest opening. Even if they don't like sweets they'll usually suck it up and feed it to the queen. Within a week or so no more ants. But besides ants, that looks like possible fert burn to me.

Again, I've never heard of regular ants devouring foliage. You might get in touch with your extension to figure out what is going on. Now, leafcutter ants don't eat foliage. They just snip it off and take it back to their nest. Were these ants CARRYING pieces of foliage? Your extension might like to know if you're seeing them. As I said, there aren't supposed to be any up north. Around here, we don't see foliage around regular ant nests because they bury it.

No never carrying they were simply slowly eating it. I feel it is simply because it is near a nest or they were going to build a nest there. Ants her never have vegetation around there nest - so thehy must kill it. That is only my theory. It is rare they get to my plants but luckily I am around enough I catch it within hours most time. It is also never mature plants only seedlings - and I think 2 of the 3 times it was this exact spot - it is a good spot for a nest.

If I see it again I will take some time and observe and get pics. Now I am curious because it would have made a lot more sense to cut it down. I think they were eating it.

If they were carrying it they were carrying very tiny pieces which I would not have noticed. When I caught it they had take off about 1/4" x 1/2" from each leaf and there were a few dozen scurrying around and many on the leaf itself.

Pic of it now, note that the one next to it is older (it emerged 1 day sooner) and is completely unharmed. Leaves have DE I put on last night then squirted water to rinse off leaves this morning.