blights originate from the soil

"Blights" is a catch-all label for disease and can't be lumped all together. Each tomato disease is specific in its cause.

Some tomato diseases do originate with the soil (like Septoria for example) but most of the fungus caused 'blights' - Early Blight, Alternaria, and Late Blight especially - are also airborne so yes, they spread.

Whether to quit treating - depending on what you mean by "treating" - and pull the plants all depends on which specific disease you are talking about. Late Blight kills the whole plant quickly but in many other cases such as Early Blight, the plants can survive and produce well with proper fungicide treatments.

Dave

Dave, I bet you meant to say Fusarium or Verticillium, for instance, for soilborne instead of Septoria Leaf Spot, which is not and is strictly a foliage bad guy. ( smile)

Other than that if one of your plants goes down with a confirmed diagnosis with a soil borne disease then it means that there's a good possibility that plants in the same area might also do the same since usually the soil in an area has that bad guy and it's not jsut the bad guy underneath the affected plant.

The main foliage pathogens are:

Early Blight ( A. solani), fungal
Septoria Leaf Spot. fungal
Bacterial Speck
Bacterial Spot

....and those four are transmitted by wind and embedded in rain drops or irrigation waters.

Then there are the insect mediated viral diseases of which there are many as well, but they don't exist in certain parts of the country since the insect vectors are not found there. Same with many of the soil borne diseases which are not found in all parts of the country.

Although not widely known at least Fusarium is known to also be transmitted by wind.

So the key to knowing what you have is proper diagnosis and one place to go is to the Pest and Disease Forum , link at the top of this page, and look at the Problem Solver thread if no one answers your questions, or better still show some pictures if you can.

Finally, I know of nothing that is effective against soil borne diseased plants, since you said above you were treating them. Varieties with tolerance such as F, for fusarium are only tolerant and live longer for a week or so more but that's enough time to get the sugar concentration up for large scale farmer's harvest. Tolerance for several seed borne diseases do exist, but those were developed mainly for the large scale commercial farmer, not for we backyard hobby growers.

Carolyn

Dave, I bet you meant to say Fusarium or Verticillium, for instance, for soilborne instead of Septoria Leaf Spot, which is not and is strictly a foliage bad guy.

Duh! Yep, thanks Carolyn. That's what I get for thinking faster than I can type. And that's hard to do at my age. :) Septoria goes later in the sentence.

Dave