Cual seria la posible causa?

Hi Adan Sandoval ! This is The collar rot disease of Tomato (Solanum lycopersicon L.) caused by Sclerotium rolfsii (Sacc.) is a severe soil born disease, particularly in the undulating red and lateritic zone causing substantial losses. For effective management of this disease remove excess moisture and drenching with Carbendazim + mancozeb (1:1) 0.25% and subsequently use of Nativo fungicide as 2nd spray It will be better if soil application of Trichoderma mixed with compost is given. All the best

Agree with Dr. V Pandey sir his diagnose is 100% correct let me give you another solution 50 gm fostyle almonium (aliette bayer)+2.5 gm coppor oxychloride or 4 gm sulpher mix both in 1 ltr water and first of all flood it 5 to 7 days use a spray of propineb+iprovalicarb as foliar for effective control of this disease however good suggestions Dr. V Pandey sir

Thanks Tufail Abbas bhai

Most welcome Dr. V Pandey sir

This screenshot explains treatment.

Tufail Abbas Dr. V Pandey Thank you very much, I will perform these treatments

Sali sir after the latest update version there is no library in plantix many of my friends have remove plantix worldwide plantix was the one app that peoples were self solving his problems in library sir do you know? Why peoples like plantix there is alot applications but peoples like only plantix because there is library and have solutions of all type of diseases so for experts its no matter but problem for those who have no experience new visitors thanks

Tufail Abbas bhai it is there but a bit different pattern to assess it. Even I am also confused

Dr. V Pandey sir lot of peoples using plantix for library i know it do not effect on experts but for new visitors its really hard many of my friends and juniors have remove plantix i just write a letter here as a complaint to Sali sir that kindly in next update update the library thanks for support

Es un sintoma mas avanzado

El suelo

Hi Adan Sandoval ! What is that small round ball like structures? is it fertiliser? If not this might be nematode galls. To check pl put a ball in a deop of watering glass slide and cut with sharp blade and observ for presence of nematodes. I have uploaded a pic for your reference. I doubt from pic that there is nematode infestation also. All the best

Dr. V Pandey probablemente sean esclerocios de Sclerotium rolsfi, era parte del hongo

Adan Sandoval I saw the round structures in pic. I am not aware about the magnification of your pic. If its that much big than definitely it's not sclerotia. If it's like small brassica seed than you are right it will be Sclerotia, the fruiting bodies of fungus. All the best

Dr. V Pandey gracias por su respuesta, el tamaño es similar a la semilla de una brassica

Adan Sandoval than you are correct this is sclerotia

Damping off

David Romero this is collor rot... big brother of damping off🤣