Boreholes in coconut rachises caused by coconut rhinoceros beetles, Oryctes rhinoceros. Mamala Bay golf course, Joint Base Pearl Harbor-Hickam. The adult beetles bore through the outer fronds to get to the growing shoot, where they feed on sap. This is the definitive sign of CRB infestation, and is also visible much earlier than leaf damage (though less conspicuous). This tree shows signs of at least three attacks; repeated attacks will eventually kill the tree.