This is an insect known as “Mango Stem borer” damaging to mango and other fruit crops. Adult survive on delicate leaves, causing no excessive damage. While, grub bore the bark of tree trunk or branches, making tunnels and subsequently enter into the stem or branch and feed inside. Excreta of grub or saw dust is coming out from the entry point which indicate the infestation of stem borer. The leaves of infested branches begin to wither and eventually the whole branch dries out. If trunk is damaged, the whole tree dries up. video source : Kishor B.Pansare