Fruit borer of litchi and longan is pest that causes fruit drop. A comparable experiment was conducted by uncovering and covering young fruits with blue nylon net throughout maturation. Covering caused 10 percent more fruit drop than uncovering and the fruit is still destroyed but less than uncovering 7 times, 85-87% which was the main cause of fruit drop, was physiological effects of the litchi trees. The same result of dissection of dropped litchai and longans, showed 82-92 % drop due to physiological effects, and only 5-7 % fruit borers. The seeds of young fruit of litchi and longan aged 14 and 19 days were eaten by fruit borers. For mature fruits, the borer could eat only at the fruit base. Eventhough, the edible part of fruit was not affected, but the damage reduced consumer satiafaction.