Signs of lack of water or excess heat?

[to be chafoin]

Oh, it is known for soils that can be deficient in Calcium, the Gironde?

On the side of the Landes, certainly: sandy soils, sometimes blackish when they are cultivated [their local name escapes me, but I knew it; I, in my youth, plowed in Gironde Bazas], acidic, so poor in Ca ++ ...

You are not known, on this side there, for your limestones!

I hasten to specify: I do not know the vineyard side!

Oh yes I see the type of soil that you speak ... On the other side vineyards, next to my home is the soil of gravels, so rather stony. But precisely where my garden is: not a single rock so I do not know, in any case it has nothing to do with the sandy land of the moors, it is brown clay bordering the Garonne. I wondered if there was not this problem of salinity, evoked as a possible cause ...

[to be chafoin]

I am aware of it, but in the case of our friend, the necessary step is first watering ...

I do not know if this is really a cause of this disease, but I read many years ago that this disease is usually caused by water stress and that this water stress is often caused by irregular watering more than by a real lack of water.
When watering tomatoes, it should be done regularly (depending on the capacity of the soil to retain water) so potentially every day and with always the same amount of water.

I have the opposite experience: my tomatoes under tunnel; never again watered until 20 days ago (the soil was soaked by the winter rains and those of May, I did not put the tarp of the tunnel until the beginning of July); there, I empty an underground tank of several m3 by pumping in the middle of the tunnel (which makes 6m X 6m); I forget ; the tank is emptied; since then I have not watered; not a black ass!

Well, I partly solved this question. Indeed the plants come from seeds of Italian origin. The person who gave them to me not only had tomatoes with a mediocre taste but also had black buttocks while she watered regularly. It seems that there are really sensitive varieties (elongated tomatoes) or even sensitive seeds. This does not prevent that there is also a phenomenon related to my soil and / or the weather that it has done ...

[to be chafoin]

Another sign on the foliage this time: related to the lack of water, to the excess of heat, or to a sun too aggressive?

This is the same variety, moreover it is on the right that I took the picture of black butts. What is amazing is the difference between the two feet from identical plants, the one on the right being exposed to the morning sun! !

[Moindreffor]

just an underground gallery for one foot to die the neighbor
I had 2 pumpkin feet watered the same, each carrying a fruit, one is doing well the other punctured pests with this heat wave begin to dig on the surface under the hay or mulch the earth becomes too hard underneath, so they have to cut some roots

[to be chafoin]

Yes I think you're right somewhere, a heat induced effect so. That said I do not understand the reasoning because the land seems rather harder on the surface because drier ... I suspected more and more voles to do serious damage. There are lots of molehills! But I did not know they were also attacking tomatoes!

[Adrien (ex-nico239)]

We can always break our heads to understand the reasons for the death of a plant but I wonder if we have the means.

[Moindreffor]

I thought more of a collateral damage, they pass and too bad for the root that is on their way

[Did67]

Another sign on the foliage this time: related to lack of water, excessive heat, or too aggressive a sun

Very unlikely.

There can not be enough water left and not enough right, so little distance. And the drought makes the leaves roll, not yellow ...

Excess heat, outside, the tomato does not know: my tomatoes in my greenhouse (not the open tunnel) have cooked up! I harvested tomatoes, mature, but cooked on the outside!

And the aggressive sun, on the tomato: never at home. She grows in Lanzarote !!!

[to be chafoin]

Very unlikely. There can not be enough water left and not enough right, so little distance. And the drought makes the leaves roll, not yellowing ... The excess heat, outside, the tomato does not know: my tomatoes in my greenhouse (not the open tunnel) have cooked up! I harvested tomatoes, mature, but cooked on the outside! And the aggressive sun, on the tomato: never at home. She grows in Lanzarote !!!

Yep, maybe the cause is elsewhere ...
I pushed this foot a bit and that's what I see

there is a whole network of roots that are on the surface in the first 2 cm of rotting hay.

I wonder if the growth problems of this foot (yellowing leaves, black ass) are not due to these roots above ground: when the hay was wet, no problem but when the roots were naked against the remains of hay dried ...!

[to be chafoin]

We can always break our heads to understand the reasons for the death of a plant but I wonder if we have the means.

Maybe not but it's still all the interest! Thanks to the transat, it is possible to go underground! When I see a video of Didier with close up shots of vole surface damage and I see him picking up his celery as he collapses the galleries, I can reasonably understand that it is the voles that plan my celery. Same thing after the video rectification where thanks to a comment from gardener Didier understands that it is not a mushroom on the roots of its salads but the sooty mold that accompanies root aphids! I can now suspect that it is aphids aphids that sucked the sap of my pdt, causing their collapse and making them fragile, or even more susceptible to mildew ... These are suppositions but it gives a track of action! Otherwise we remain blind and on the surface ...