Why the Watermelon fruit is infected..

This might be due to inadequate pollination. Sprinkle jaggery solution (1 kg per 10 liters of water) with the help of Neem branch. These jaggery solution droplets will attract pollinators and thus pollination may be carried out.

Venkat Pawar. Sir, Does high temperature affect the small melons.. In our area the temp is near 40-42 °C..

Usually in flowering stage dropping may be possible but after setting I don't think any problem will occur

Venkat Pawar.sir, My watermelon plot is of 48 days now..., have 8000 plants..., but having only 5000-6000 fruit in now conditions.. Will the fruits will increase after some days.

Sagar check fruit setting on 12th or 14th node. If female flowers are there then nothing to worry.