Q: I’m growing tomatoes in a spot that gets full sun, is well drained, and the block retaining wall allows excessive water to drain out. Initially my plants were doing great.
Now not so good. The lower older vines have wilting leaves that are turning brown and black and falling off. Also the upper leaves have spots on them and what ever is killing my vines is getting worse.
A: It looks like septoria leaf spot.
If it makes you feel better, my vines have it too and look exactly like yours. The black leaves hanging on the vine are identical to your pictures.
Sad to say, there’s not much we can do once the disease is this far along. It’s typically a “wet summer” disease. If we have lots of rain or regular overhead irrigation, septoria will start its invasion.
Good gardeners learn to keep an eye on the weather and to be preventative. If you saw this starting in June, you could have sprayed the vines with chlorothalonil (click for sources) to stop the spread.
Lacking that, we just have to say “There’s always next year!”