Overwinter recovery in perennial crops: Insights from Pierce's disease and related pathosystems

Pierce's disease (PD) of grapevines, caused by the bacterium Xylella fastidiosa, is a major constraint on viticulture in various regions of the world. An unusual and understudied feature of PD is the capacity of some grapevines to recover after winter dormancy, becoming asymptomatic and the bacterium is no longer detected in the plant. Ovewinter recovery has been documented for over four decades and is reproducible under both field and controlled conditions, yet outcomes vary across cultivars, environments, and pathogen strains. Similar phenomena have been reported in related pathosystems, including X. fastidiosa infections of almond and phytoplasma-associated diseases of grapevine, providing comparative insights. We review ecological and biological factors that influence overwinter recovery, highlighting the role of winter climate, timing of infection, host cultivar differences, pathogen population dynamics, and vector activity. Evidence suggests that overwinter recovery is not solely attributable to cold-induced pathogen mortality but also involves host-mediated processes, potentially including an immune reset during dormancy. These findings link recovery to broader ecological consequences, influencing pathogen persistence, disease epidemiology, and the geographical distribution of PD under current and future climate conditions. Despite decades of observation, the mechanistic basis of recovery remains unresolved. Key gaps include the identification of host traits underlying recovery, the contribution of pathogen genotype, and the integration of climate variables into predictive models. Addressing these gaps will be essential not only for understanding disease ecology but also for anticipating the impact of climate change and informing management strategies for PD and related vector-borne vascular diseases.