P-213 - Investigating the spread of aggressive strains of Neopestalotiopsis in the Southeastern United States via molecular testing in the 2024-2025 season

Neopestalotiopsis leaf spot and fruit rot has become a pressing issue in strawberry fields in the US. Historically, Neopestalotiopsis species were known to be weak pathogens, often isolated from roots and crowns. However, recent outbreaks in commercial fields across the Southeast have highlighted the aggressive nature of the pathogen. The “aggressive strain” of Neopestalotiopsis sp. has caused severe leaf and fruit symptoms and plant decline and mortality. Morphological characteristics cannot be used for identification; hence, molecular detection assays are the only reliable method for diagnosis. To assess the distribution of this pathogen, a multi-state survey was conducted in 2024-2025. Symptomatic strawberry samples (n=57) from AR (n=5), GA (n=34), IN (n=3), LA (n=11), MS (n=1), and NC (n=3) were tested. Fungal isolates were recovered from leaves, roots, crown and fruit.  A total of 169 isolates were analyzed, of which 46% (n=77) were confirmed to be the aggressive strain.  In addition, 6 isolates from GA were confirmed to as a “second aggressive strain” collected from Appling, Bibb, Camden, and Wilcox counties. The aggressive strain was detected in all states, except from MS, with a proportion ranging from 21% (AR) to 100% (NC). The emergence of new “aggressive strains” has complicated the diagnosis and management of this disease. Efforts are underway to develop a new molecular test using multi-locus sequencing capable of distinguishing the two aggressive strains from non-aggressive strains, which will enhance diagnostics and enable more targeted management strategies.