pathogens Review Aphrophoridae Role in Xylella fastidiosa subsp. pauca ST53 Invasion in Southern Italy Ugo Picciotti 1,2 , Nada Lahbib 1,3,4 , Valdete Sefa 1 , Francesco Porcelli 1,5, * and Francesca Garganese 1   Citation: Picciotti, U.; Lahbib, N.; Sefa, V.; Porcelli, F.; Garganese, F. Aphrophoridae Role in Xylella fastidiosa subsp. pauca ST53 Invasion in Southern Italy. Pathogens 2021, 10, 1035. https://doi.org/10.3390/ pathogens10081035 Academic Editors: Stefania Loreti and Marco Scortichini Received: 21 June 2021 Accepted: 12 August 2021 Published: 16 August 2021 Publisher’s Note: MDPI stays neutral with regard to jurisdictional claims in published maps and institutional affil- iations. Copyright: © 2021 by the authors. Licensee MDPI, Basel, Switzerland. This article is an open access article distributed under the terms and conditions of the Creative Commons Attribution (CC BY) license (https:// creativecommons.org/licenses/by/ 4.0/). 1 Dipartimento di Scienze del Suolo, della Pianta e degli Alimenti, University of Bari Aldo Moro, 70126 Bari, Italy; ugo.picciotti@uniba.it (U.P.); nadalahbib48@gmail.com (N.L.); valdetesefa@gmail.com (V.S.); francesca.garganese@uniba.it (F.G.) 2 Department of Marine Science and Applied Biology, Laboratory of Plant Pathology, University of Alicante, 03080 Alicante, Spain 3 Faculty of Sciences of Tunis, University of Tunis El-Manar, Tunis 1068, Tunisia 4 INRAT—National Institute of Agronomic Research of Tunisia, Laboratory of Plant Protection, Rue Hédi Karray, Ariana 2049, Tunisia 5 CIHEAM—Centre International de Hautes Etudes Agronomiques Méditerranéennes, Mediterranean Agronomic Institute of Bari, 70010 Valenzano, BA, Italy * Correspondence: francesco.porcelli@uniba.it Abstract: The Philaenus spumarius L. (Hemiptera Aphrophoridae) is a xylem-sap feeder vector that acquires Xylella fastidiosa subsp. pauca ST53 during feeding on infected plants. The bacterium is the plant pathogen responsible for olive quick decline syndrome that has decimated olive trees in Southern Italy. Damage originates mainly from the insect vector attitude that multiplies the pathogen potentialities propagating Xf in time and space. The principal action to manage insect- borne pathogens and to contain the disease spread consists in vector and transmission control. The analysis of an innovative and sustainable integrated pest management quantitative strategy that targets the vector and the infection by combining chemical and physical control means demonstrates that it is possible to stop the Xylella invasion. This review updates the available topics addressing vectors’ identification, bionomics, infection management, and induced disease by Xylella invasion to discuss major available tools to mitigate the damage consequent to the disease. Keywords: bacterial diseases of non-wood plants; environmental IPM; alien; invasive; quarantine 1. The Insect-Borne Plant Pathogen Xylella fastidiosa Wells et al., 1987 (Xf) [1] is a xylem-restricted “fastidious” bacterium that lives in plant xylem and foregut vector lumina [2–4] of some xylem-feeders auchenor- rhynchan [5]. Some phytopathological characteristics related to Xf (e.g., diversified range of plant hosts) are due to the ability of the bacterium to acquire DNA from the environment through horizontal transfer [6]. Xf is able to infect more than 300 different host species including crops, ornamental and spontaneous plants [7,8]. In addition, Xylella strains can recombine among themselves [9,10], enriching the gene pool. The genetic diversity of Xf strains allows them to infect several plants species but rarely diseasing them lethally. The bacterium may play a role in plant health, causing nonspecific water shortage symptoms or damage by plugging the xylem vessels [4,11–14]. Moreover, Xf uses part of its vector’s cuticle as a nitrogen source employing enzymatic chitinase to dissolve exoskeleton [15]; the vector also ingests xylem sap [16] for nitrogen and carbon sources. Xylella fastidiosa is an exotic pathogen introduced in Europe by the trade of asymp- tomatic coffee plants from Costa Rica [17]. Schaad et al. [18] proposed three Xf subspecies: Xylella fastidiosa subsp. fastidiosa, previously named Xylella fastidiosa subsp. piercei (type strain ATCC 35879T, causing grape Pierce’s disease); Xylella fastidiosa subsp. multiplex Pathogens 2021, 10, 1035. https://doi.org/10.3390/pathogens10081035 https://www.mdpi.com/journal/pathogens