Lexie I assume since you have been here for a couple of years that you know there is a Tomato Growing forum, right? If not you may want to check it out for all the information there on your question. It is linked on this forum's front page.

That said, "blight" is a catch all term many use to cover any and all plant diseases so first it is important to determine exactly which of the several foliage diseases you actually have. The prevention and treatment for them differ.

IF indeed you are having a problem with the disease Early Blight (a. solani) rather than Alternaria of Septoria or B.Speck or Spot then please understand that Early Blight is caused by a fungus which can live in the soil but is also airborne. And just because it lives in the soil doesn't mean your plants will get the disease unless all the other ambient conditions are just right too.

Crop rotation plays a relatively minimal role in preventing it since the fungus is airborne. Several other factors play a much more important role. These are detailed in most any of the info management pages on a. solani on the web and discussed in even greater detail on the Tomato forum.

Briefly they are proper plant spacing for good air circulation, proper plant pruning to remove any and all leaves that may contact the soil, the use of thick layers of mulch around the plants, proper levels of soil nutrients, no excess watering, and most importantly - no over-head watering - water only at soil level. The regular use of a fungicide spray to prevent infection from the rain and air is also strongly recommended.

What other plants are susceptible to a solani? Potatoes, peppers, eggplants, etc. or basically anything in the nightshade family including nearby weeds.

But first as I said get a confirmed, professional diagnosis from your county extension service or local Master Gardener service as Early Blight is often confused with some of the bacterial diseases and the control of them is different.

Hope this helps.

Dave

Yes, I do know there is a tomato forum but since my main question was what other plants blight can affect, I didn't see the need to post this just in the tomato forum. That said, I have been told by a master gardener that what I have is early blight. I have looked at many, many pictures of diseases since I got this last year and the only two that match my plants is the Early Blight (a. solani)and the Alternaria of Septoria (just looked that one up from your posting). It definitely is not the B. speck. And I not only rotate my crops but also have the plants spaced a good ways apart, they have a thick layer of mulch, have had my soil tested before the season this year, only water from below, prune off any leaves / branches that look like they have it and since I just saw it this year I haven't sprayed them with a fungicide but plan on it. (I did that last year). My question was what other plants can be affected by it besides tomatoes and potatoes. I didn't know peppers could also get it, which would explain some things since I have two bell pepper plants nearby that are starting to have the same effects and I didn't know that was what it could be. I will be getting some fungicide to see if it improves. In the meantime, I have thought about calling the county agent, do they actually test it or how can they tell me for sure what it is?