Chemical Treatments Tested Against Xylella fastidiosa: Strategies, Successes and Limitations

Xylella fastidiosa (Xf) is a Gram-negative bacterium responsible for severe diseases in several commercially significant crops, including olive, grapevine, citrus and almond. Its management is particularly challenging due to its transmission via widespread vector insects, its ability to form biofilms, its high genetic diversity and, sometimes, latent symptoms. Current control strategies focus on integrated and preventive approaches, including the use of resistant varieties, agronomic practices, and vector control through chemical and biological methods. Direct control of the bacterium has always been a complex challenge that includes strategies to limit vector presence and activity in the field; however, several compounds have recently been evaluated that are able to inhibit biofilm formation and Xf growth. This review provides an up-to-date summary of studies investigating the efficacy of various treatments based on organic compounds, synthetic molecules and salt- or metal-based formulations. By evaluating the results of in vitro and in vivo experiments, the most promising solutions were identified that address the main challenges and limitations of chemical control strategies. These include N-acetylcysteine and zinc- and copper-based formulations, which are effective and potentially transferable to the field for crops such as citrus and olive trees. Antimicrobial peptides and nanoparticles, on the other hand, have demonstrated high efficacy in vitro, although further studies directly in the field are required. The evidence emerging from the analyzed studies offer insights to guide future research towards more effective and sustainable management approaches to mitigate the spread and impact of Xf.