I'm not sure what this could be, I've been having the same issue with 2 store-bought tomato plants. I talked to the people there and they said I over watered them-so I let them dry out a bit, then put more water when they were actually dry-they have just gotten worse. They also have black spots on them.

I apologize for not being able to help, but I'm watching to see if anyone else might know what this could be.

Your plant looks good. I see tomatoes. Your mix looks good and so does your container size. One leaf dying isn't the end of the world. How much sun do they get? How often do you fertilize and with what? Can't really tell but the leaves maybe could be a little darker green, but it's hard to tell from the angle and lighting. But overall it looks like a good plant. Sometimes I'll have a leaf or two die and sometimes not. It gets hot near the surface of the top of your container mix.

Thanks for the responses, everybody. I do tend to overwater, so I'll keep an eye on that.

My first thought looking at the leaves of your tomatoes was that they needed watering, or maybe they have been overwatered. Do you check the moisture of the growing medium 3-5 inches below the surface?

Watering in a container is much different from watering a plant in the ground. Do you have one of those saucers that usually go with that kind of pot? If so when you water your plant, wait about 30 minutes and then drain that saucer. If you leave water standing in it, you are depriving the tomatoes of air for the roots and they will drown.

GardenWebber sprouts_honor (Jennifer from Cleveland) had a wonderful suggestion on how to tell whether or not you need to water your tomatoes, and I quote here: "Get a wooden dowel rod (or two) and sink it in the ground near a plant or two and leave it. Pull it out when you think you need to water. If the top is dry and the bottom is a little damp, it's time to water. If it looks dark and feels saturated, wait to water. I use this technique with potted plants that don't like being over watered and it's helpful with in ground plants too."

Also when you water a plant in a container, the process tends to wash away the nutrients in the growing medium so they will need to be fed frequently. Many container growers use a water soluble balanced fertilizer such as 8-8-8 or 10-10-10, diluted to 1/3 or 1/4 recommended label strength and use it to water every 10 days to two weeks.

Good luck with your tomatoes.

Betsy

I know you likely have this figured out, but I had a similar experience this year when we turned from 20,20,20 to 9-15-30 we send that through drip irrigation. Each plant only sees about a quart of water each week.
I have to purge lines and always end up with a gallon of concentrated solution. In this case I filled the 5 gal bucket with water to dilute it and poured it over the last 4 plants in the row. They recovered within the week. My point? In my case I wasn't giving enough nutrients or water.

I had the same problem. Tried some fung oil and this may have helped a little. We kept getting a lot of raining humid days this year. I trimmed off all effected areas and disposed of them. This helped for a while, but has finally taken over even into my cherry tomatoes and zucchini... Any thoughts to prevent this next year???

My tomatoes and cucumbers have done the same thing. Plenty of bloom and fruit at the periphery but the tomatoes don't have a chance to turn red before the foliage dies around them. I pick small green tomatoes and they turn red on my window sill. Here is a pic. I think I over fertilized them at planting. What is funny though is my neighbor just across the fence has the same symptoms!

There are several common tomato diseases. You begin by Google 'common tomato plant diseases'. Most all growers have to deal with at least one of them every year so it is important to learn about them. They are caused by air borne fungi and bacteria. They can be prevented to a degree by the regular use of fungicides from the day of plant out. But they cannot be cured once established, just slowed down long enough to get the harvest on the plant.

It is impossible from your photo to even begin to guess which your particular disease is since the photos are not close enough but your research into those common diseases should narrow it down for you.

One thing you should never do is leave all the diseased and damaged foliage on the plants. Had you stripped it off as it developed you could have slowed the progress down substantially. Now it is likely to late to save the plants as it is far to advanced.

http://vegetablemdonline.ppath.cornell.edu/DiagnosticKeys/TomLeaf/TomLeafKey.html

Dave

Thank you for the reply Dave. I grew up on a farm and we had a bountiful garden. I can plant sugar cane and hot peppers but didn't learn about tomato disease.

Why are my tomatoes dying from the bottom up?

would it make you feel better if they were dying from the top down? The older leaves are on the bottom dying of old age. the leaves at the top are younger leaves that will die when their time comes.

why do old people die before young children? same question same answer.

Not really a helpful answer. Bottom leaves can be dying from any number of causes, and unlike simple old age, many of them are fixable. So the question shouldn't just be shrugged off.

Dave