Mitigating grapevine esca disease: an innovative integrated management strategy to reduce incidence and severity by enhancing plant physiology and defence mechanisms.

Esca is one of the most destructive grapevine trunk diseases and a growing challenge for viticulture worldwide, particularly in the context of climate-driven increases in disease expression. Due to the lack of curative solutions and the limited efficacy of currently available preventive measures, there is a pressing need for sustainable, field-ready strategies capable of mitigating disease impact. In this study, we assessed the performance of AF5, a novel foliar formulation composed of potassium acetate, α-tocopherol, and propylenic glycol, applied throughout the growing season. Field trials were conducted over three consecutive years in three vineyards located in distinct pedoclimatic areas of northern Italy. Across all sites and seasons, AF5 consistently reduced esca incidence and severity, with decreases ranging from 26 to 40% and 35% to 50%, respectively, compared with the conventional management protocol adopted by each winery. To investigate the physiological basis of this mitigation, we measured leaf-level gas exchange in symptomatic and asymptomatic vines. AF5-treated symptomatic plants displayed higher stomatal conductance and transpiration than untreated symptomatic vines, indicating a partial alleviation of the hydraulic limitations typically associated with esca-induced xylem dysfunction. To complement these observations, RNA sequencing of leaf tissues revealed a clear transcriptional activation of defence-related pathways in AF5-treated symptomatic vines. Genes involved in pathogen perception (e.g., receptor-like kinases), ethylene and jasmonate signalling cascades, and immune-regulatory transcription factors such as WRKYs and FRK1 were strongly induced, suggesting that AF5 enhances host defensive preparedness. Overall, this study provides the first multi-year, multi-site evidence that AF5 can reduce disease expression while supporting physiological performance and activating key immune pathways. These results position AF5 as a promising, easily implementable tool for integrated esca management in commercial vineyards.