2017 ASHS Annual Conference

Indian Laurel-leaf fig (Ficus microcarpa L. f.) and its numerous forms and cultivars are iconic street trees in California. Until about ten years ago they were disease free. In 2005 symptoms started to appear on street trees in Santa Monica, Los Angeles and other Southern California coastal cities. Canopy thinning, tip dieback leading to branch dieback, complete tree defoliation and death were wide spread by 2015. In 2012, Mayorquin and others identified the following species of Botryosphaerales class fungi to be causing canker disease in this fig: Botryosphaeria dothidea (Moug.) Ces. & De Not, Neofusicoccum luteum (Pennycock & Samuels) Crous, Slippers & A. J. L. Phillips, N. mediterraneum Crous, M. J. Wingf. & A. J. L. Phillips, and N. parvum (Pennycock & Samuels) Crous, Slippers & A. J. L. Phillips. Typical fruiting bodies found in cankered wood are perithecia (teleomorphic stages) and pycnidia (anamorphs). No conidia are formed on coastal infections. Recently, in another development, F. microcarpa in the Coachella Valley in the California low desert were observed with the disease sooty canker, typically associated with the pathogen Neoscytalidium dimidiatum (Penz.) Crous & Slippers, which is a known human pathogen of skin in tropical countries, but unknown to cause human disease in California. N. dimidiatum is thermophyllic, occurring in trees growing in very hot desert landscapes, and causes spreading cankers on the main stem and major branches. Unlike the disease in coastal regions, young branches appear not to be affected initially. N. dimidiatum only produces conidia and the teleomorphic Botryosphaeria stage is not observed where it occurs. Adequate control of these diseases in Ficus is unknown; however, it is recommended to prune out affected branches early and to maintain sanitized pruning equipment to help prevent disease spread. Stress factors, such as age, pruning, wounding, and other damaging horticultural practices, might predispose trees to these diseases. Photo: Ficus branch dieback (D. R. Hodel).