Ok unconventional solution. Try it or not.. Continue to remove the affected leaves and make sure there is plenty of air circulation around the base of your plants by removing lower leaves and limbs and weeds.

I thought the rain was great till, my zucchini and tomatoes started an early mold/ blight..... yellowing of leaves and dying.. But I found a dirty little secret no one wants us to find out about.. Someone in South America discovered spraying milk on your zucchini, cucumbers, melons and tomatoes prevented, mold, milky spore and tomato blight. The study I read suggested a 10-30% mixture of milk to water was optimal... 1 part milk to 9 parts water in a spray bottle works fine. With all the rain we have been having you may have to reapply but is sure is alot safer and cheaper than fungicides. It seems the natural bacteria in milk somehow combats the mold and blight in addition to building the plants immunity by absorption through the leaves.
According to the study I read, this milk solution was 90% effective and a whole lot cheaper than traditional copper, fungicide etc. According to a New Zealand study on the same solution they found that skim milk was just as effective as whole milk and as a result of the lower fat content also reduced the possibility of an odor problem.

It seems to be working well so far for me... let me know if anyone else has any luck with this...

Tomatoesaretops,
did you ever get an answer to this question ? I share your pain. did you find a fungicide or anything that stops the spread once it starts ?
Thanks,
Brad

I have just recently tried this on my tomatoe plants. It seems to help with the fungus. I have sprayed my plants 2 times. However, the plant that had it the worst is still not producing any fruit. There have been some flowers, but they fall off the plant after they bloom. I am going to continue with applying the milk/water solution and see what happens...

I think my plants are starting to get a fungus as well. Do I just put the milk in a spray bottle, and do you spray all your tomatoe plants or just the ones that seem to be effected? Also is there a better time of day? Early morning or late evening?? Some of my plants, the leaves are yellowing and then when I turn them over they have black dots, it looks like mildew or something I guess. By the way, non of my plants but my cherry tomato plant is giving me any fruit. I thought it was too hot here, but other people around me are still getting tomatoes and have been for some time. So I've been researching and this sounds like something I have. I just wanted more specifics since I have never gardened before. I'm definately not ready to give up, I'm sticking with my babies until the very end. So any help is greatly appreciated.