What type of disease is this in my mango plant at the time of flowering?

Hi Mahesh Patel . It's Mango mal farmation. Control measures:  1. As soon as the disease appears, the affected terminals along with the basal 15-20 cm healthy portion should be removed or pruned and burnt. 2. If more than 25 per cent affected plants, de-blossoming at bud burst stage should be done to delay the flowering 3. Spraying of Planofix (200 ppm) during the first week of October followed by deblossoming at bud burst stage is recommended 4. A single foliar application of 1,000 ppm cobalt sulphate prior to flower bud differentiation successfully reduce the floral malformation. It's also associated with Leaf Miner Flies . Check by clicking on green link for knowing symptoms and taking control measures.