To find out the main cause of dead branches of Myrica rubra Sieb.et Zucc at Wenzhou ruian, Zhejiang province, tissue isolation was conducted on dead branches and one fungal isolate HN–01 was separated. According to the morphological characteristics, spore size, microscopy and the sequence of the internal transcribed spacer (ITs), the strain HN-01 was identified as Pestalotiopsis sydowiana. Based the rule of Koch′s postulation, P. sydowiana was proved to be the pathogen causing the exsciccation of myrica sp. branches. Four major fungicides were screened against the pathogen in laboratory and 50% prochloraz WP had good control effect with 50% effective concentration value of 1.21 mg/L.