Blight in my indoor seedlings? How did this happen?

So my tomato seedlings are not doing so well. Yellowing leaves, with little brown spots that look suspiciously like early blight. My big question is, if this is blight, how the heck did it happen? I started the seeds (which I bought from fedco last year, and had no problems with last time around - they caught the blight in the field just like everybody else's tomatoes) in sterile seed starting mix, and potted them up into organic potting mix, both of which I bought this year at a local greenhouse. I bleached all my trays and six-packs before seeding.

I've attached some pictures so y'all can see what's going on. Is this blight? Where did it come from? I thought that blight needed live plant material to overwinter. I do have some potatoes in the cellar that might have blight spores on them, but they haven't been near my seedlings...I'm at a loss, and pretty grumpy about all the work I put into these plants. Should I just throw them all out (and all the peppers and eggplants too) and buy transplants this year?

Fungal spores are endemic -- meaning everywhere. Once fungi sporulate, they don't need any live material to remain viable. If you have ductwork in your house, that's all it takes for spores to get from the basement to the seedlings are. Now that I've got you terrified that spores are lurking everywhere to get you, relax, it's not all that bad. You need to have a lot of spores attacking weakened plant under the right conditions, and then the disease symptoms show up (usually when it is too late to do anything about it).

Your pictures don't look like the classic symptoms of early blight, at least as described by University of Maine extension. Could be a minor pathology that the plants will be able to fight off with some help. Have you tried bacterial compost tea as a foliar spray? Those "right conditions" that plant pathogens require include being uninterrupted in doing their dirty work. If you add competing bacteria with a foliar spray, that may be enough to dislodge the suspected pathogen.

If I had to guess, I'd say it's a little bit of stress, maybe from potting up. It could also be a burn on the leaves. Maybe some sunlight got reflected in a funny way and fried some spots.
I'd say plant them out and see what happens.

John Elliott wrote:Fungal spores are endemic -- meaning everywhere.

While I agree with the gist of everything that John wrote in his reply, and even the concept he is getting at in the small above quote, the word endemic means locally prevalent; it does not mean everywhere. An animal endemic to the Galapagos, for instance, is only found there.

Is this blight? Where did it come from?

EARLY BLIGHT: "is characterized by irregular brown spots with concentric rings in a target pattern on the lower leaves. These spots soon enlarge to a quarter to half inch, run together and cause the leaf to turn brown and usually to drop off the plant." ..."overwinters in tomato debris, jimson weed, horse nettle, ground cherry, or nightshade (family)."
Tomato seed can have the fungi on it, but usually from diseased plants.

Burn your diseased plants.

There are resistant varieties of tomatoes that maybe you should look into since it's a problem where you live:
Manalucie, Southland, Floradel, Floramerics, and Manahil.

A three year rotation in soil planting location is recommended.


Most of this came from Roger B Yepsen Jr's The Encyclopedia of Natural Insect and Disease control published by Rodale.