First report of Neofusicoccum parvum causing Juglans neotropica dieback in Costa Rica

During the rainy season in the province of Cartago, Costa Rica, Juglans neotropica (walnut) trees showed symptoms of dieback. Isolations were made from the zone of symptom progression of these diseased trees on FDA plus antibiotic culture medium and the pathogen Neofusicoccum parvum was identified morphologically and molecularly (ITS4-ITS5 primers). The disease caused by this pathogen was confirmed by pathogenicity tests, where the plants inoculated with the fungus, reached lesions of up to 51.5 mm, unlike the control that presented 7.8 mm, showing a significant difference (alpha <= 0.05) and a normal distribution among the variables. This is the first report of N. parvum causing apical death on J. neotropica in Costa Rica.