Location: Horticultural Crops ResearchTitle: First report of Phaeobotryon cupressi causing canker of Calocedrus decurrens (incense-cedar) in Oregon
|SNIEZKO, RICHARD - Us Forest Service (FS)|
|WISEMAN, MICHELLE - Us Forest Service (FS)|
|SERDANI, MARYNA - Oregon State University|
|PUTNAM, MELODIE - Oregon State University|
Submitted to: Plant Disease
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 4/1/2016
Publication Date: 8/1/2016
Citation: Weiland, G.E., Sniezko, R., Wiseman, M., Serdani, M., Putnam, M. 2016. First report of Phaeobotryon cupressi causing canker of Calocedrus decurrens (incense-cedar) in Oregon. Plant Disease. 100(8):1793. https://doi.org/10.1094/PDIS-03-16-0313-PDN.
Interpretive Summary: A new canker disease was discovered on incense-cedar, a native tree of Oregon. Infected trees have dead branches scattered throughout the tree crown, eventually leading to a sparse canopy and destroying the ornamental value of the tree. We consistently isolated the fungus Phaeobotryon cupressi from symptomatic trees located throughout the Willamette Valley in western Oregon. We confirmed that the fungus was capable of causing disease by inoculating healthy saplings. One to 1.5 months later, cankers developed on inoculated branches and caused the branches to die. We were able to reisolate the pathogen, proving that P. cupressi was the pathogen responsible for the disease. Phaeobotryon cupressi has previously only been described from Iran on cypress and from Kansas (USA) on juniper. Our research is important because this was the first time P. cupressi has been identified causing disease of incense-cedar in Oregon.
Technical Abstract: Since the early 2000’s a canker disease has been noticed with increasing frequency on landscape specimens of native incense cedar (Calocedrus decurrens) planted throughout the Willamette Valley (from Portland south to Eugene) in western Oregon. Symptoms initially appear as dead and flagging small-diameter branches (= 1cm) 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 of branches affected increases and the disease progresses up the crown. Symptoms are often more extensive on younger trees affecting a larger proportion of the crown and killing larger diameter branches. In 2014 and 2015, a canker pathogen, Phaeobotryon cupressi, was consistently isolated from branch cankers on 45 trees from 13 locations along 200 km of the Willamette Valley. Isolates were identified on the basis of 99% internal transcribed spacer (ITS) sequence identity and 98% translation elongation factor 1-a (EF1-a) sequence identity to the extype specimen of P. cupressi GenBank Accession No. FJ919672 (1), and on the basis of morphology. Six isolates from several locations were used to inoculate healthy, 0.6-1m tall saplings of incense cedar grown in 11L pots in an outdoor canyard. Approximately 4-6 weeks after inoculation, branches inoculated with P. cupressi began to turn brown and die, while negative control branches remained green and healthy. The pathogen was reisolated from all inoculated branches using the same procedures described above, but was never isolated from negative control branches. Thus, Koch’s postulates was fulfilled. This is the first report of P. cupressi occurring on incense cedar in Oregon. The pathogen was originally described causing cankers on Cupressus sempervirens in Iran and has been isolated once from Juniperus scopulorum in Kansas, USA. Similar symptoms have been observed on incense cedar in its native range in the Cascade mountains of Oregon, but it is unknown if P. cupressi is the causal agent at those locations.