Pleochaeta Prosopidis Powdery Mildew on Neltuma alba Nurseries in the Gran Chaco Dry Forests (Argentina)

In forest nurseries, maintaining plant health is essential for producing high-quality seedlings. Effective sanitary management relies on continuous monitoring throughout the crop cycle. Powdery mildew, caused by fungi in the Erysiphaceae family, extracts nutritional plant reserves, thus reducing its productive potential and causing significant economic losses due to lower yield and quality. Although Erysiphaceae has not been yet studied in some natural ecosystems, such as the Chaco region of Argentina, information from these natural ecosystems is critical. This research aimed to comprehensively study Pleochaeta prosopidis isolates from Neltuma alba and to assess the relationship between disease incidence and seedling quality in nursery conditions. This pathogen exhibited a partially endoparasitic life cycle, causing damage to the mesophyll of infected leaves. The phylogenetic analysis of the 28S rDNA sequences from N. alba seedlings with powdery mildew signs grouped with the reference sequence corresponding to Pl. prosopidis. The highest levels of disease incidence and severity occurred during winter and in plants kept in the nursery for over nine months (p < 0.001). Infected seedlings showed a significant reduction in height and diameter at neck height (p < 0.007), indicating a clear decline in quality. This study provides the first comprehensive description of Pl. prosopidis in N. alba, highlighting its impact on seedling development and nursery productivity.