The definitive symptoms are usually seen best with a close up of the affected leaves so that would help greatly. It is the shape of the spots, any halo coloring, and their distribution along the leaf veins that often distinguishes one disease from the other.

The basic treatment for most of the common ones is the same - remove and dispose of all affected foliage and begin a regular spraying program of the fungicide of your choice.

There are many links posted here to disease diagnosis sites you can browse for pics to compare to your plants. Once of the best is http://aggie-horticulture.tamu.edu/vegetable/problem-solvers/tomato-problem-solver/leaves/

Dave

thank you for your help. I will look at the link you provided.

Meanwhile I will post close up pictures of the leaves.

if you think you know what is it. please let me know.

Regards. Stef, zone 5A

It looks to me like alternaria Canker .

what do you think ?

http://aggie-horticulture.tamu.edu/vegetable/problem-solvers/tomato-problem-solver/leaves/alternaria-canker/

thank you

stef, Montreal, zone 5A

I'd have thought it was Septoria / Early Blight which we get every year. It blows in on the wind and rain. To slow it down a bit, I pick off all the dead and diseased leaves. It also helps to put mulch down to prevent splashback from the soil.

Linda

I agree with digs comments about how to deal with the situation. Certain varieties are more prone to septoria and other fungal/bacterial diseases. Always keep water off the leaves...it is a major concern for tomatoes.

thank you. next year I will have a black polyethylene tarp over my earth and watering from a cutdown pcv pipe next to each plant..... that should help right ?

The black tarp will help. I grow some of my tomatoes under black plastic and I find that they don't need much watering once they have become established.

Linda