Cultivar Susceptibility and Environmental Parameters Affecting Symptom Expression of Red Leaf Blotch of Almond in Spain

Red leaf blotch (RLB) of almond, caused by Polystigma amygdalinum, is an important foliar disease this nut tree in the Mediterranean basin and Middle East regions. In recent years, incidence has increased Spain, corresponding to increases area newly planted orchards use susceptible cultivars. 2009, experimental orchard including 21 almond cultivars was at Les Borges Blanques, Lleida, northeastern Spain. No fungicide treatments were applied during 10-year period (2009 2018) order allow natural development. Cultivar susceptibility RLB assessed each year, from 2011 2018, through visual observations symptoms naturally infected trees. The results led us classify into five groups. most Tarraco, Guara, Tuono, Marinada, Desmayo Largueta, Soleta, whereas Mardía tolerant. annual positively correlated with accumulated rainfall spring, especially April, while it negatively high spring summer temperatures, May. These findings could be used improve management strategies identifying improving timing application.