First Report of Sirococcus conigenus on Deodar Cedar in Oregon.

Abstract

Cedrus deodara is a highly valued conifer widely grown as an ornamental in the Pacific Northwest and southern United States. C. deodara in the Pacific Northwest is normally problem free but occasionally is damaged by dieback of shoot tips, which has been associated with a fungus resembling Sirococcus conigenus. In February 2002, bleeding cankers were observed on 2- to 4-year-old stems of potted nursery stock of C. deodara cv. Karl Fuchs from Clackamas County, OR. Cankers were dark with indistinct margins, shallow, and up to 30 cm long. Infection appeared to have originated with small twigs that had died. Cultures isolated from discolored bark on streptomycin-amended potato dextrose agar (PDA) produced conidiomata with hyaline, fusiform, two-celled conidia typical of S. conigenus (1,3). Inter-simple sequence repeat-polymerase chain reaction fingerprints of an isolate from one of these trees were consistent with the P group of S. conigenus (mostly from hosts in Picea and Pinus spp.) (2). This isolate (02-04, ATCC MYA-2969) was used to inoculate two shoots on each of 12 3-year-old potted deodar cedars in each of two trials. Removing a needle wounded each shoot, and an agar plug colonized with mycelium was placed over the wound and held in place for 2 weeks with Parafilm. Sterile agar plugs were applied to two wounded control shoots on each tree in each trial. After 10 weeks, 25 of 48 inoculated shoots were blighted and drooped with yellow to brown needles that eventually dropped. The pathogen was reisolated from 24 of 25 symptomatic shoots but not from asymptomatic or control shoots. To our knowledge, this is the first confirmed report of S. conigenus as a pathogen of C. deodara.