Identification, pathogenicity, and fungicide screening of <i>Neofusicoccum parvum</i>, causal agent of a new branch blight disease on Fujian cypress (<i>Fokienia hodginsii</i>)

Abstract Fujian cypress is a precious and endangered coniferous species. Since 2019, Fujian cypress trees in Anxi County, Fujian Province have suffered a novel lethal disease. This disease initially manifests as twig wilting of one or several branches, which then extends to all branches, leading to tree death within one or two months. The branch blight is associated with stem bark rot and discoloration of the cambial tissue. Pathogenicity tests showed that five fungal isolates could induce stem bark rot and cambial discoloration on branches in vitro, and their representative isolate Fhb-2 caused branch blight and sapling death symptoms that were similar to those observed in naturally infected trees. By combining morphological characteristics with phylogenetic analysis based on partial sequences of translation elongation factor 1-α (tef1-α), internal transcribed spacer regions of ribosomal deoxyribonucleic acid, and β-tubulin, the five pathogen isolates were identified as Neofusicoccum parvum. Additionally, the sensitivity of isolate Fhb-2 to seven fungicides was assessed. The assessment revealed that thiophanate–methyl exhibited the strongest antifungal effect on N. parvum, with an EC50 value of 0.011 μg ml−1, followed by flusilazole with an EC50 value of 0.057 μg ml−1. As far as we are aware, this is the first report of N. parvum causing branch blight disease of Fujian cypress, and triazole and benzimidazoles are proposed for disease control.