There is a great possibility that this is a heavy Alternaria solani infection.

Hi: It is seem Alternaria solani infection

Hi

you are right but i think this disease may be caused by downy mildew. what do you think about it

This disease caused by so many factors but the picture shows that heavy infestation of mealy bug cause the damage of tomato plant . 

Symptoms sometimes trick even the most experienced professionals in pest control. A precise diagnosis is essential for recommendation of control measures. We can have some guesses, like the ones indicated, to which I include bacterial diseases, such as leaf spot (Xanthomonas spp.) and physiological disorders. I suggest start by eliminating some of the possibilities based on further informations, such as spray schedule, symptoms on fruits, putative resistant cultivar, etc. Then, proceed with laboratory simple procedures, such as a moist chamber followed by microscopic examination for fungal structures, direct observation of insects and mites, microscopic observation of bacterial exsudation from the borders of leaf leasions, among others. And then, if it is not a common pest in the region, proceed the Koch's Postulates in case a pathogen is isolated from the lesions. 

i agree with lopes but   it may be a leaf spot disease caused by fungi such as Alternaria, Septotia etc.  

No it is not the infection due to mealybugs, if infection is due to malybug then there should be whitish waxy substances but these are not here the spots are angular which are characteristics of late blight. So if it was early blight then the spots should coalsce which is not here. I think you should do some tests for late blight

I agree with you, Mehi Lal, I just mentioned other possibilities, since Alternaria has been mentioned in previous answers. Actually, I do believe that Alternaria and Septoria are strong candidates, among others. 

It seems to me that has a mass of spores on the plant surface. This white mass suggests the presence of powdery mildew.

This is a combination of several agents mainly pathogenic (leaf spots) and nutrient deficiency (Phosphorus and other micro nutrients).

Thanks for responding my question

I don´t think that it is Alternaria. You should look carefully the symptoms. You should look also the roots, inside the stems, not only the aerial part. I think that could be one root problem by fungi or bacterium, but the photo is not clear. I think also that we look on the leaves can be Oidium, Leveilulla or Passalora fulvum but probably they are such saprophytes, maybe the main causal agent will be in the root zone.

I agree with Carlos, please don't jump into conclusion without more detailed observation.That symptom is not picture perfect to lead towards any classical fungal, bacterial, or viral diseases of tomato. Where was that picture taken? Is this a processing tomato?

Dear, It looks as fungal infection. You should place the plant in sprayed by water plastic bag and wait for mycelium development. Then detach it with needle and look in microscope. If you see sectioned, bottle shaped conidia (usually, in chains) it is Alternaria.  Alternaria develops target shaped spots on leaves. Here could be other fungus. You should check in microscope.

It looks like Early blight to me too. In that case, you should see dark brown to black colored, multi-cellular pear or oval shaped conidia under a microscope.

Looks very much like a fungal infection at least. Would have been good to have a picture of the whole or some part of the field. Early and late blight infections of this severity are usually on the whole field..........Did you also observe these symptoms on the fruits, either stem or blossom end?.......Are these dry lesions or slimy/watery?.....Syngenta provides Ridomil or Ridomil Gold.........a broad spectrum fungicide.

For me, it look likes of Alternaria solani or Alternaria tomentosa (the same fungi) on tomato. The symptôm on the photo are not good. I think there are symptôms of  Early Blight  cause by pathogen fungi . On leaves for example  are concentric cerles. The individuel conidia  pluricellulaire  in oval  form with  tail can grow on PDA media and are brown and not in chain We observe  under microscope  .We observe some symptom again on fruits.

Its not possible to say exactly which fungus is it but in my view it may b Septoria blight or may be chances of Alternaria blight too. needs further confirmation via lab test.

Symptoms were only at the upper side of the shoots?

Did you spray the plants with any chemical or fertilizer?

Have been extreme weather conditions?