First Report of Phaeobotryon cupressi Causing Canker of Calocedrus decurrens (Incense-Cedar) in Oregon

Since the early 2000s, a canker disease has been noted with increasing frequency on landscape and windbreak specimens of native incense-cedar (Calocedrus decurrens) planted throughout the Willamette Valley in western Oregon. Incense-cedar is valued in low-input landscapes where the disease destroys their ornamental value. Symptoms initially appear as dead, flagging small-diameter branches ([< or =]1 cm) that are scattered throughout the lower crown of the tree. Cankers are constricted with a clear demarcation between living and dead tissue. Over a period of several years, the number and diameter of branches affected increases as the disease progresses up the crown. Symptoms are often more extensive on younger trees and affect a larger proportion of the crown. In 2014 and 2015, Phaeobotryon cupressi was consistently isolated from branch cankers on 45 trees from 13 locations along 200 km of the Willamette Valley. Branch cankers were disinfested for 1 min in 10% bleach, 1 min in 70% ethanol, and then plated on half strength PDA amended with streptomycin at 50 mg/liter (1/2 SPDA). Isolates showed 99% identity with the rDNA ITS sequence (KU896860 to 896863) and 98% identity with the translation elongation factor 1- alpha (EF1- alpha ) sequence (KU896864) of the ex-type of P. cupressi, GenBank Accession No. FJ919672 (ITS) and FJ919661 (EF1- alpha ), respectively (Abdollahzadeh et al. 2009). Morphological characteristics were consistent with the species description. Cultures were olive brown to gray on PDA. Conidia, produced within pycnidia, were hyaline to brown, thick-walled, oval, aseptate, and measured 27.1 (20.0 to 32.5) x 14.1 (10.0 to17.5) mu m from both branch cankers and cultures grown on PDA (4 isolates x 50 spores). Six isolates from several locations were used to inoculate 0.6 to 1 m tall saplings of incense-cedar grown in 11 liter pots, outdoors. Inoculum was produced by growing each isolate on 1/2 SPDA for 1 week at 22[degrees]C. For each isolate, two branches were inoculated on two saplings (four branches total) by excising a thin slice of bark (3 mm super(2)), placing a 5-mm-diameter colonized plug on the wound, then covering with Parafilm. Negative controls were inoculated with uncolonized agar plugs. All inoculations were repeated at least 3 weeks later. Approximately 4 to 6 weeks after inoculation, branches inoculated with P. cupressi turned brown and died, while control branches remained healthy. A dark, sunken necrotic lesion extended from th