Pecan bacterial leaf scorch (PBLS) is an economically important disease of pecan and is caused by the slow-growing bacterium, Xylella fastidiosa subsp. Xylella leaf scorch is a bacterial disease caused by the pathogen Xylella fastidiosa. The Xylella fastidiosa is a bacterium recently introduced in Europe. Pierce’s Disease (PD) of grapevines, caused by Xylella fastidiosa subsp. This test system is based on a mixture of antibodies from three serologically distinct isolates of Xf. This bacteria is believed to spread by insect vectors, such as leafhoppers . This ELISA test is a reliable tool for detection of Xylella fastidiosa, the causal agent of bacterial leaf scorch, Pierce's disease, and phony peach. It is especially virulent in olive tree, it affects numerous plants, trees and fruit trees.. For now is not known cure or effective treatment against the disease.. It can also be spread from grafting with infected plant tissues or tools. The therapeutic and prophylactic efficacy of a phage cocktail composed of four virulent (lytic) phages was evaluated for control of PD. Xylella fastidiosa has a wide plant host range and spectrum of insect species capable of serving as vectors which should increase the bacterium's invasiveness and make it difficult to prevent introduction via live plants from the tropical or subtropical Americas. fastidiosa (Xf), is a limiting factor in the cultivation of grapevines in the US.There are presently no effective control methods to prevent or treat PD. Xylella fastidiosa is native to North America, and there are several different subspecies of the bacteria that impacts a large plant host range. multiplex (Xfm).