Investigation of a Novel Foliar Disease on Maackia amurensis in North Dakota and Its Subsequent Survey

Abstract

A new, undescribed pathogen was observed on Maackia amurensis (Amur maackia or Chinese yellow wood) trees in Fargo, North Dakota, over the course of four growing seasons from 2016 to 2020. Affected trees showed visual signs of necrotic lesions ringed with a yellow halo of various sizes on leaves which began in midsummer and persisted into the fall. Diseased material was collected in October 2020, from which single spore isolations were taken. After a third-party DNA analysis, the causal agent was tentatively identified as an Alternaria species. Curious about the full extent of the host and fungal pathogen, a survey was designed and distributed to horticulture industry professionals, botanical gardens, and arboreta in September 2021. The survey results showed where M. amurensis, its cultivars, and related species were growing and where similar symptoms were observed in other regions throughout the United States.