The most common foliage diseases are Septoria Leaf Spot and Early Blight, and both are fungal . the other two are Bacterial Speck and Bacterial Spot, which are of course due to bacteria.

The word blight is a general one and is used by many to describe a sick plant without ever making a diagnosis to see what the specific problems are.

What I don't see on your list of products you use is chlorothalinol, known as Daconil, which is THE best antifungal known and works very well against grey mold, fungal foliage dieases,etc.

Yes, it's synthetic, but has a lower toxicity than does Rotenone, which is organic and is approved by all organic certifying agencies that I know of.

If nothing has worked for you in the past I do sugggest you try Daconil, get the concentrate bottle that has about 29.6 % active ingredient, before you dilute it.

And it's important to know that it must be used as a preventive since it and all other anti-fungals I know of, organic or not, cannot CURE foliage fungal diseases.

Just noting that I don't want to get into any discussions here about synthetic vs organic. There's a Forum for that here.

My own opinion is that there are some synthetics that are not good and some organic products that are not effective for everyone everywhere, as in one size does not fit all.

Below I've linked to a Google search for oxidate products and so many of the links say it gives total control of both fungi and bacterial foliage infections, but I think that's a bit of hype since no product I know of ever gives TOTAL control of anything. Too many variables.

Carolyn, who has been to S CA and knows what the most common diseases are and also has known Laurel Garza for a very long time, that means before she ever started her plant business.

mid summer, leaves start with the yellow blotchy leaves that turn brown and eventually spread throughout the plant.

Could easily describe many things, some of which are not diseases but soil-based problems. And as already mention "blight" IS fungal. Can you provide a more specific/detailed description?

And whichever product you decide to use it has to be applied regularly from the day of planting out to be effective. Once the symptoms appear it is usually too late for any of them to be effective.

Dave

there could be a lot of things going on that your LA hot weather is triggering in your soil. you need to know you PH,P-I,K-I,ca%,Mg% and by doing the test they will give you recommendations for tomato plants. i have my soil is tested every year..

as for Oxidate, i been using it for about 5 years now with a injector system. Oxidate and Zerotol and others are "hydrogen Dioxide" and is a "DANGER" label. this stuff will mess you up if you don't know what you are doing.

dose it work for me? yes but i use it on a regular basis even before i see any foliage diseases.

also with your Powder mildew, grey mold...that sort of thing..
try Potassium bicarbonate, " NOT!! Sodium bicarbonate=baking soda"
Potassium bicarbonate is safe and can used in a back-pack sprayer as a foliar application.