Looks like Early Blight. That's my best guess. Last year it was bad here and this year it is just starting. I get decent crops anyway even with Early Blight but I'm fairly sure I could have even better ones if I sprayed chems. Just not worth it to me, my family and the environment IMO.

I am organic. My advice is to never water the leaves, only the roots. Plant 4 to 5 feet apart if you don't prune. Use lots of compost. Use a thick organic mulch. This has worked pretty well for me.

You say you spray Daconil every two weeks. The Daconil Fan Club here on this board will tell you to step up your spraying is my prediction.

Yes it does look like Early Blight. If you use Daconil then make sure you get both sides of the leaves. Early Blight here is intense as the rains caused quite a splash. Like bigdaddyj suggests, a thick mulch helps greatly in the prevention. Oh, and use your Daconil weekly and especially after a rain. Best of luck.

i have never had early blight. i think the reason is two fold. first i feed and water my tomatoes heavy. they are hungry critters. second is i prune the leaves early and often.
it also might be that we grow our own plants from seed in our green house.
we are dedicated to helping local people grow food. this year we gave away over 10,000 vegetable plants.

wiring man

Thank you for the advice! This is probably a really dumb question.... but does the mulch help because rain doesn't bounce back up onto the bottom leaves? That could be my problem because I have black fabric around the plants to keep weeds down but only a thin layer of grass clippings on top.

Is early blight in the soil? Is there anything that I can till into the soil for the winter that will help me next year? Sorry, I feel like a total amateur.... :))

The fungus spends the winter in infected plant debris in or on the soil where it can survive at least one and perhaps several years. It can also be seed borne. New spores are produced the following season. The spores are transported by water, wind, insects, other animals including man, and machinery. Once the initial infections have occurred, they become the most important source of new spore production and are responsible for rapid disease spread.

A thick mulch indeed does help against splashback and also serves to keep moisture in. A good organic mulch will also decompose and compost in place. Compost makes for healthier plants which are better at fighting off diseases.

In fall I clean-up as best I can by removing all plant material. I use a straw mulch and remove that as well and place into the compost pile. I then lasagna compost with a mix of grass clippings, shredded leaves and new compost on top. I plant right through that in spring and then straw mulch again.

see I have something almost identical looking to that, but it's only on 1 tomato plant and it hasn't spread the entire year.

It's on my potato leaf plant...and I just prune the ugly looking leaves off and everything has seemed fine. I'm starting to have TONS of fruit set & TONS of flowers still forming.