It almost doesnt matter. Treatment is the same. Remove affected leaves and spray with a fungicide. Daconil is widely used but there are many.
It looks like bacterial speck. Try a copper-based fungicide.
Cole- I actually like copper much better. And the product I use does not have any temp restrictions which is helpful where I live.
Actually, it does matter. If it's a bacterial infection, Daconil has no effect.
Sorry to disagree but even if it is bacterial Daconil can be as effective as many other fungicides even though copper based ones are more commonly recommended for bacterial issues. The real issue with bacterial diseases is that not much of anything works all that well. About all you can do is try to get ahead of it and keep the plant going for awhile.
A close up of the leaves would be of great help in identifying the issue. At first glance Bacterial Speck would have been my guess too I'm sorry to say. But I downloaded the pic and blew it up as much as possible and the leaves in the lower R corner look like Early Blight. So it could be either or or both.
Either way, you must strip off all the infected foliage and begin spraying with your fungicide of choice. If it is EB it will improve somewhat and shouldn't affect the fruit. If it is Bacterial Speck then it will continue to spread most likely and will show up on the fruit as well.
Meaning no disrespect at all, I have the Daconil info booklet in front of me. Under "Crop - Tomato, Diseases Controlled" there is no mention of bacterial spot or speck.
A quote from Carolyn in a previous thread:
"it doesn't matter if it's Bacterial Speck or Spot b'c both would be treated the same way. And about the only thing a home grower has to use are copper containing preps such as Kocide, or similar."
I'm not trying to argue or debate, just trying to learn.
Basically I agree with you Rob. I'm just coming at it from a different direction. The pessimistic "nothing really works" direction.
IME with treating speck and spot none of the fungicides do much - are equally ineffective I mean. Some the old farmer cures like dusting with lime or spraying with a dilute peroxide solution may be just as good.
But on the off chance the disease is mis-diagnosed or that fungus issues are also present then Daconil will be more effective. Or as Darrel suggested recently, alternate the two, cover all the bases. :)
Sorry I didn't say that more clearly before.
Mine have the same specks, too. From talking to others, it has been a problem this year in southern California, but I haven't heard exactly what it is.
Here is a link that might be useful: tomato problem solver
Sounds like a fluke that copper seems to be slowing down whatever is ailing my maters! I think I originally bought it for bacterial speck. Question came up on another forum re copper fungicide and I have heard before that copper kills bacteria, so not to use it with, say Serenade. So, does it actually kill bacteria or does it work (supposedly) more as protecting unaffected leaves?