Detection of Xylella fastidiosa in Host Plants and Insect Vectors by Droplet Digital PCR

Spatial-temporal dynamics of spittlebug populations, together with transmission biology, are of major importance to outline the disease epidemiology of Xylella fastidiosa (Xf) subsp. pauca in Apulian olive groves. The spread rate of Xf is mainly influenced by (i) the pathogen colonization of the host plant; (ii) the acquisition of the pathogen by the vector from an infected plant, and its inoculation to healthy plants; (iii) the vector population dynamics and abundance at different spatial scales; (iv) the dispersal of the vector. In this contribution we summarize the recent advances in research on insect vectors’ traits – points (ii), (iii), (iv) – focusing on those most relevant to Xf epidemic in Apulia. Among the vectors’ bioecological traits influencing Xf epidemic on olive trees, we emphasize: natural infectivity and transmission efficiency, phenological timing of both nymphal and adult stage, the role of semi-natural vegetation as vectors’ reservoir in the agroecosystem and landscape, preferential and directional dispersal capabilities. Despite the research on Xf vectors carried out in Europe in the last decade, key uncertainties on insect vectors remain, hampering a thorough understanding of pathogen epidemiology and the development of effective and targeted management strategies. Our goal is to provide a structured and contextualized review of knowledge on Xf vectors’ key traits in Apulian epidemic, highlighting information gaps and stimulating novel research pathways on Xf pathosystems in Europe.