Question: query regarding management of fruit rot and drop in watermelon. 
Answer: at first spray borax 6 gram/liter of water 3 times @ 7 days interval in the evening time. by maintaining of 3 days gap spray neem oil 5 ml/liter of water at 5 days interval continously up to the end of the season. after completion of 3 spray of borax, continue one vitamin like- mohaphol/sagorika/biovita 2 ml/liter of water @ 15 days interval up to the end of the season in the evening time in the absence of rain.