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These dark spots have appeared on my tomatoes. I assume it's some sort of desease, but can't quite figure out which one.

Here are a few pictures: enter image description here enter image description here enter image description here enter image description here

And a few notes:

  • the colour of the spots is a bit inconsistent - some look like just black dots, while others are spots with a bit of a brownish tone and sometimes it's a black dot on one of these brown spots
  • none of them have a white center
  • there are no white or yellow halos
  • the leaf gradually turns lighter and more and more of these spots will appear until the leaf dries completely
  • it usually starts more around the edges of the leaf rather than the center
  • oddly enough the middle part of the plant is where it usually starts (ie not from the older bottom leaves nor the younger top ones, but somewhere in between)
  • it doesn't look like there's a set direction in which it travels (ie to towards the bottom or top of plant), so I assume it's just whatever leaves are nearest?
  • the fruit and stem are both unaffected

And another note: when the spots first appeared they all looked slightly purplish, but now they are all in the brown (or black) tones (even the newest ones)

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I'd class it as some sort of blight (fungal attack) (without knowing which one, particularly) and cut out the affected leaves ASAP.

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    I'll add: please don't compost the affected leaves -- put them in a plastic bag in the trash. Next year, plant tomatoes in a different spot and perhaps try a resistant variety. Aug 28 at 18:28
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    It's not late blight, and doesn't look like septoria. It's also not mosiac virus. Unless the leaves yellow, you probably don't need to remove the leaves.
    – Jurp
    Aug 28 at 20:35
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    Yes, it's clearly not behaving in the classic modes or early or late blight. Particularly the "starts in the middle" does not match up. It appears to be yellowing the leaves, and leaving it hanging around until they yellow more, brown, or fall off provides more material to infect other leaves with whatever it is. So I'll stand by "remove them when you see it" without knowing exactly what it is.
    – Ecnerwal
    Aug 29 at 12:43

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