Some of my tomato seedlings are getting what looks like hardened brownish stems at the base. They were kept in cells for a very long time, since I knew when I repotted they'd get huge and it was too early, so I don't know if that is what contributed to it. They seem otherwise healthy and are growing fine. I'm potting them up now, but wondering if this is something else, like early blight on the stems. I feel like I've had this before and it wasn't an issue, but maybe folks have some input on what it is.

That looks like scarring. Did you have any pests during their time in the small pots?

I know I've had slugs make an appearance under my pots before.

Sure looks like something's been nibbling on the stems. What could it be? But it doesn't look like fresh nibbling, maybe they've moved on.

[mention]zendog[/mention] I had a similar problem last year and I had never seen this before. It happened after I planted my seedlings in the garden and it also happened to a few pepper seedlings. I posted the photos on 2 forums and did endless Google searching and the only thing that people came up with was damping off.

I cut off several of the tomatoes and rooted them in water and they recovered and grew fine but I also tried piling soil around a couple of the other tomato plants to get them to grow roots above the brown area and they also did fine. The peppers died.

If this happens again this year I will just plant them deeper.

I cut open a stem on one of the tomato seedlings and the brown area seemed to be present throughout the stem. The tomato plants themselves were starting to wilt indicating a lack of food or water moving through the brown area.

20200608_195457 by Brownrexx, on Flickr

Pepper damping off by Brownrexx, on Flickr

Thanks all. I guess it could be some type of scarring or irritation of the stems since I really don't see anything impacting the leaves.
I did have some aphids early on that I got rid of with Neem, so maybe that was part of it. I think they'll be fine planted deep then, so that is good news

If they do anything significantly different after planting I'll update this post.

Damping off can be transferred to the garden in a previous year and come about after healthy seedlings are transferred to the garden in a later year.
This is what experts on the subject told me a few years ago.