Further evidence that calcium, magnesium and seaweed mixtures reduce grapevine leaf stripe symptoms and increase grape yields

Summary. Grapevine leaf stripe disease (GLSD) is the most important syndrome of the esca disease complex. GLSD foliar symptoms are associated with grapevine yield losses and decline in vigour of host plants. Relationship between incidence and severity of GLSD symptoms and reductions grape quantity and quality has been demonstrated. In 2010–2012, foliar applications of mixtures of fertilizers based on calcium, magnesium and seaweed reduced symptom expression and increased yield quantity and quality. In the present study, mixture applications were carried out in 2013-2015 in different vineyards located in Abruzzo and Emilia-Romagna Regions (north-central Italy). These treatments reduced GLSD symptom incidence and severity, and applications of seaweed without calcium and magnesium was not effective. This confirmed involvement of the nutrients in the reduction of leaf symptom expression. Mechanical properties and absorbance difference measurements demonstrated increased berry quality from vines treated with the mixture. In trials carried out in 2015, the efficacy of the mixture applied in tank mix with other pest and disease control products was not reduced. We conclude that applications of calcium, magnesium and seaweed mixtures are effective for reducing the impacts of GLSD in vineyards.