Abstract: Xylella fastidiosa, the causal agent of the devastating “olive quick decline syndrome”, is a xylem-inhabiting gram-negative bacterium that was introduced into the Apulia region of southern Italy. Xylella fastidiosa caused an epidemic outbreak and catastrophic dieback of olive groves. This pathogen is transmitted exclusively by xylem fluid-feeding sap insects, the main vector being the meadow jumping beetle Philaenus spumarius. The use of microorganisms such as entomopathogenic nematodes and fungi is a well-known biocontrol strategy against agricultural pests. This study aims to evaluate the pathogenicity of two different entomopathogenic fungi (EPFs), the commercial Beauveria bassiana strain ATCC74044 (Naturalis®) and Lecanicillium muscarium Ve6 (Mycotal®), and two indigenous strains of EPNs against juveniles of the meadow spittlebug Philaenus spumarius. Monitoring of insect vectors is necessary to prevent the further spread of Xylella fastidiosa in Europe. The rapid spread of Xylella fastidiosa underlines the importance of preventive biocontrol measures against the vector with EPNs and EPF.