Plant stem is shrinking and dying how to control it?

Hi Darshan ! This is Foot and Collar Rot disease in your tomato plant. For details please click the link above to plantix library. You can use copperoxychloride +Carbendazim (1:1) 0.25% as drenching or Tebuconazole and Trifloxystrobin combination fungicide to effective control of this disease. Please don't forget to use Trichoderma mixed in good compost to give as soil treatment. Thanks for visiting plantix community