My jowar seedlings are dying with the central leaf dried, dead heart problem

A dried central shoot, the dead heart symptom, in young jowar seedlings along with small whitish maggots and a rotten smell at the base is the classic sign of shoot fly attack. The fly lays eggs on young seedlings and the maggot bores in and kills the growing point, and the loss is highest in late sown or thin, slow growing crops. Pull a few affected seedlings and check the base for the maggot to confirm, or send a photo to your KVK or agri officer. The strongest defence is cultural: sow early and at the right time so seedlings cross the vulnerable stage quickly, use a slightly higher seed rate and thin later so you still have enough healthy plants, and remove and destroy the dead heart seedlings. Seed treatment at sowing with a recommended systemic insecticide is a common protection your officer may advise. If a spray is needed on a standing crop, follow the label dose, the pre-harvest interval and the local KVK recommendation and rotate the mode of action. Early sowing usually beats this pest more reliably than any spray.