The invention relates to system conceived and designed to identify pieces of fruit, especially citrus fruits, affected by any amount of rot and to determine the automatic expulsion of these pieces from the conveyor moving them through the installation. The system comprises illuminating the fruits with UV-A band light in a computer vision unit, and capturing images of the illuminated fruits by means of a camera to send them to a general control member in order to detect fluorescences associated to the rot effect. The identified fruit is automatically expelled from the conveyor in an expulsion unit, the position of the defective fruit being determined with the aid of an encoder associated to the conveyor. The general control member is a PC type computer, equipped with specific application software.