Bad advice resulted in lost tomato plants

[Rogue11]

A friend of mine called today asking me to come by and see what was wrong with her tomatoes.
She had seen my plants last year and wanted to grow some of her own. Since I remembered how much her daughter loved to pick some cherry tomatoes in my garden I gave her 5 extra seedlings that I had grown. I also helped her prepare the ground for when they would be ready for planting. A few days later she told me she had bought 2 more, larger plants that were already blooming, since my seedlings are still only 4 -5 inches high.
Anyway when I got there today all the plants, her large ones and the potted seedlings were covered in spots that looked very much like Early Blight. She told me she had seen a few spots on the plants she had bought (a Black Prince and a Mr. Stripey) but when she asked someone at the store he told her that was just fertilizer burn and not to worry about it.
While she was out of town for 2 days she had put the smaller potted plants behind the larger plant to protect them from the rain and wind that we were expecting. I guess that's how all the seedlings got infected so fast; the rainwater and the wind probably blew a ton of spores onto them.
But is it really possible for Early Blight to develop so quickly (it's been a week since she bought the infected plants and 5 days since the rain)

I can't believe the guy at the store didn't recognize that the plants were diseased. Or maybe he did and just didn't care.

[Kisal]

Anything to make a sale!

Was it a big-box store, by any chance?

[Rogue11]

Yes it was Home Depot

[Kisal]

Perhaps you can turn this sad experience into a learning situation for your friend? Maybe you can suggest some reputable local garden stores or nurseries, so she'll know where to go if she wants to purchase plants in the future?

Maybe you could help her find a couple of healthy plants to buy? It might be easier on you, than watching plants you nurtured from seed be less than optimally cared for. Just a suggestion, of course.

[rainbowgardener]

To account for the speed this all happens, the plants she bought were likely infected with the blight already when she got them. Here's a little bit from an article about septoria and blights:

All are fungal diseases spread by spores, which require dew or rain to infect the plant. These are most severe in wet weather. ... These diseases spread rapidly and are difficult to control once established.
https://www.ppdl.purdue.edu/PPDL/expert/tomato-blight.html

After the trouble we've had with tomato blights across the country the past couple years, I would be very hesitant to buy a tomato plant from a big box store. It does seem like the diseases are getting spread by the huge commercial growers.

[Rogue11]

Maybe you could help her find a couple of healthy plants to buy? It might be easier on you, than watching plants you nurtured from seed be less than optimally cared for. Just a suggestion, of course.

Yes, that's what I am planning on doing. We will go to the local nursery this weekend where I get all my herbs. They not only have nice plants but also offering free gardening classes (tomato growing, pruning etc) once or twice a month.

Now my question is about the soil. How large an area would have been affected by the disease? Would it be possible to dig up the ground and replace it? The problem is that the spot I had picked for her tomatoes was the only one in her garden that gets a lot of sunshine. The rest of the sunny area has grass, and somehow I have a feeling her husband would not appreciate me digging up his lawn

[Rogue11]

To account for the speed this all happens, the plants she bought were likely infected with the blight already when she got them. Here's a little bit from an article about septoria and blights:

Thanks for the link, that was a very interesting read. But it doesn't say how fast a plant can be infected. I had looked at several articles on the web last night and couldn't find an answer.

Yes I am pretty sure her plants were already diseased when she bought them, but what surprised me was the rapid speed with which the seedlings were infected. They only had 3 sets of real leaves yet, but those were almost completely covered in black spots when I saw them.

[Bobberman]

I would look close and see if those are aphids. They will spread real fast and do fly but are hard to see! They are very small and get a magnifying glass and look at them! Stores are noted for having them on most of their plants and flowers!

[Rogue11]

No, I was talking of spots from Early Blight.