Why is the fruit damaged?

Hi Neelkanth Muchahary ,It is chrysomelid beetle also known as leaf beetle . They feed on leaves . By the use of systematic insecticides(are water-soluble, so they easily move throughout a plant as it absorbs water and transports it to its tissues) you can control them easily .    

Mast

Melon fly, use pheromone traps

Install vegetable fly pheromone trap. It will help to reduce number of vegetable fly in and around the cultivated area/field.

Hii