An optical fiber distributed acoustic sensor (DAS) system for detecting a red palm weevil and/or its larvae inside a tree. The system includes an optical fiber that is configured to be placed next to a tree; and a DAS box optically connected to the optical fiber and configured to receive a reflected light from the optical fiber. The DAS box includes electronics that extracts from the reflected light a frequency in a range of [400 Hz, 4 kHz], and sends a message indicating a presence of the red palm weevil and/or its larvae inside the tree.