Epistemic diversity and the politics of knowledge in plant disease management: Insights from the <scp> <i>Xylella fastidiosa</i> </scp> epidemic in southern Italy

Societal Impact Statement Xylella fastidiosa is a major plant pathogen affecting crops such as grapes, citrus, almonds, and olives, with potentially severe consequences for agricultural production and rural livelihoods worldwide. This paper examines the conflict around the management of the X. fastidiosa outbreak affecting olive trees in southern Italy. We show that the conflict cannot be reduced to a confrontation between science and “science denialists” but involves multiple actors holding different forms of knowledge and values. Our findings highlight the importance of recognizing epistemic diversity for more resilient, socially robust plant health governance in an era of climate change and emerging plant diseases. Summary This paper analyzes the epistemic and political dimensions of the conflict around the management of the Xylella fastidiosa epidemic in Apulia, southern Italy—one of the most contested episodes in European plant health governance. The study draws on 6 years of ethnographic research, combining interviews with scientists, farmers, and policymakers; participant observation at international conferences and local assemblies; and analysis of scientific publications, policy documents, and media coverage. We identify five different intersecting domains where knowledge politics unfolds: (1) the dispute over disease causality, naming and framing; (2) the tension between scientific and lay actors regarding legitimate knowledge and research hypotheses; (3) the internal disagreements within the scientific community, reflecting different disciplinary traditions; (4) the divisions among farmers, reflecting divergent economic strategies, cultural attachments, and visions of agricultural futures; and (5) the institutional dynamics shaping knowledge production within scientific institutions. Under high uncertainty and stakes, technocratic governance struggles to secure legitimacy. Acknowledging epistemic diversity and embracing epistemic pluralism—integrating multiple forms of knowledge—is essential for adaptive and trusted plant health strategies in an era of rapid climate change and globalized trade.