Entomopathogenic endophytic fungi, a potential novel dual-action approach for the containment of Philaenus spumarius, the main vector of Xylella fastidiosa in Europe

The meadow spittlebug Philaenus spumarius is the main vector of Xylella fastidiosa in Europe. In Apulia (Southern Italy), it transmits the subspecies X. fastidiosa pauca, the causal agent of Olive Quick Decline Syndrome, which has led to the death of over 10 million olive trees. Vector control currently involves spring tillage targeting juveniles in the herbaceous cover and insecticide applications against adults. However, these approaches raise concerns about environmental sustainability. Entomopathogenic fungi (EPF) represent a promising alternative, offering direct insecticidal activity and potential indirect effects when acting as endophytes (EEF). EEF can colonize plant tissues and induce systemic resistance through secondary metabolites or immune priming, potentially affecting pest development and survival. This study aimed to: (i) assess the insecticidal activity of 20 EPF strains against juvenile stages of P. spumarius; (ii) evaluate the insecticidal activity of the most effective strains on adults; and (iii) investigate the endophytic capacity of selected strains and the associated indirect effects on the vector. The results showed some EPF strains with strong pathogenicity and endophytic potential, supporting their use in integrated vector management. Endophytic colonization may enhance pest suppression and further studies could pave the way to a novel, dual-action approach to P. spumarius control.