First report of Lasiodiplodia theobromae causing stem canker of Fraxinus americana.
In July 2017, lesions appeared on the branches of 4-year-old Fraxinus americana grown in a new nursery in Xuzhou, Jiangsu Province, China. The disease incidence was over 32% (352 investigated trees). The lesions formed on one side of the branches (15.88 ± 8.56 cm) and were reddish or dark brown. The bark was dehydrated and cracked in the later stage. The xylem and phloem tissues became brownish, which could lead to the death of the whole plant. The mortality rate was 5%, which affected the commercial value of the trees. The causal agent was isolated from 35 diseased branch samples (~4 cm in diameter and 15 cm in length) exhibiting typical symptoms and was identified as Lasiodiplodia theobromae based on its conidial morphology as well as internal transcribed spacer (ITS) and elongation factor 1 alpha (EF1-a) sequences. This is thought to be the first report of L. theobromae causing stem canker of F. americana in China.