Tomato Pests & Diseases Growing Tomatoes

Leaf spots on tomato seedlings

4 years ago

A few days ago (April 28) I noticed that some spots I had previously seen on one of my Sungold seedlings seemed to be spreading / getting larger:

I was alarmed and destroyed the plant to try to prevent spread to my other seedlings. Before that, the plant (a Sungold) was quite vigorous. All my tomato seedlings were started March 7 and this one was perhaps a foot tall and otherwise doing quite well.

Yesterday I noticed that another of my Sungold seedlings was showing spots, although they look a bit different:

These plants are grown indoors under lights, in a grow tent, with a ventilation fan continuously exhausting from the tent to keep temperature and humidity similar to the rest of the house. I have perhaps a dozen other tomato seedlings (including two more Sungolds) and so far haven't noticed issues with them. I also have several tomatillos and a wide variety of pepper seedlings and haven't noticed this affecting any of them.

I have been avoiding wetting the foliage when I water the plants, and so far they haven't been outdoors in the rain or very high humidity. I have taken them all outside a couple of times, for a couple of hours each time, to start hardening them off. I am in zone 6b, Pennsylvania.

Any ideas what is happening here? Should I get rid of the second plant too?

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Comments (2)

Labradors
4 years ago
last modified: 4 years ago
I don't know, but I checked the dreaded Late Blight and I don't think it is that as it says "large dark brown blotches with a green/green edge".

According to this: Gray mold of tomatoes | UMN Extension

"Gray Mold apparently thrives in the high humidity of high-tunnel and greenhouse settings". I've had G.M. on outside plants, and managed to save them by removing the affected branches.. Perhaps just removing the leaves would do the trick since you have noticed it early......
michael19 thanked Labradors
michael19
Original Author
4 years ago
Thanks, I was particularly worried about late blight, but the second plant in particular doesn't look right to me...the light tan dead spots don't match up, I don't think. I also don't see anything fuzzy on/around the affected areas, so I'm not sure it's a mold.

Maybe it's sunburn? I hesitate because I thought sunburn didn't usually have such well-defined borders (even a few smaller round spots!), but I've spent a couple of hours looking at tomato disease photos and I can't find ones that look like this. Possibly they got a few droplets of water on them when I was using the hose nearby to spray down a tarp, and that focused the light into those little spots or something...

I think for now I will wait a little longer and see if it progresses further than it already has. If the patches don't enlarge, then it seems more likely something like sunburn.
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