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Research Project: Integrated Disease Management of Exotic and Emerging Plant Diseases of Horticultural Crops

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Title: First report of Gnomoniopsis idaeicola causing cane wilt and canker in commercial blackberry fields in Oregon

Author
item Stockwell, Virginia
item Shaffer, Brenda
item McGhee, Gayle
item Hardigan, Michael

Submitted to: Plant Disease
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 12/28/2021
Publication Date: 12/28/2021
Citation: Stockwell, V.O., Shaffer, B.T., Mcghee, G., Hardigan, M.A. 2021. First report of Gnomoniopsis idaeicola causing cane wilt and canker in commercial blackberry fields in Oregon. Plant Disease. https://doi.org/10.1094/PDIS-11-21-2397-PDN.
DOI: https://doi.org/10.1094/PDIS-11-21-2397-PDN

Interpretive Summary: Oregon is the leading producer of blackberries in the United States. Recently, growers reported that plants in sections of their commercial fields of 'Columbia Star' and 'Black Diamond' blackberries in Oregon were suddenly dying. The growers called the phenomenon 'Blackberry Collapse.' In one field, we estimated that 17% of the plants were dead. We isolated fungi from lesions on affected plants. In addition to fungi that cause the common, non-lethal 'cane diseases' in Oregon, we isolated a fungus called Gnomoniopsis idaeicola. Interestingly, the fungal species, G. idaeicola, was first described on wild Rubus in Oregon and Washington by a mycologist in 2008, but its potential ability to cause plant diseases was not studied. Unfortunately, G. idaeicola was recently described as a very damaging cane blight fungus with high lethality to blackberry in Serbia. This blackberry cane disease (or Blackberry Collapse) is a new and evolving situation in commercial blackberry fields in Oregon. We are currently conducting surveys to determine the prevalence of disease and the pathogen G. idaeicola in Oregon blackberry fields.

Technical Abstract: Oregon is the leading producer of blackberries in the United States. Recently, Oregon blackberry growers observed that ‘Columbia Star’ plants in semicircular patches in their fields were wilting and dying, a phenomenon they called ‘Blackberry Collapse.’ The symptoms of diseased plants include lack of vigor and necrotic cane lesions near the base of petioles on the cane. In addition to common cane pathogens, Gnomoniopsis idaeicola was frequently isolated from lesions. G. idaeicola grew as white or cream-colored circular colonies with sparse to dense aerial hyphae. Some isolates exuded cream-colored conidial masses. Perithecia and ascospores were not observed; molecular methods were used to identify the fungus. Sequences of ITS, ß-tubulin, and tef-1a of eight field isolates were 100% identical to G. idaeicola sequences in GenBank. After isolation of G. idaeicola from ‘Columbia Star’ in Marion County, the pathogen was isolated from symptomatic ‘Black Diamond’ blackberry plants in fields in Washington and Linn Counties in Oregon. Pathogenicity of G. idaeicola isolates was confirmed with formation of expanding necrotic lesions on inoculated ‘Columbia Star’ primocanes and potted plants. G. idaeicola was described as a new species from collections of perithecia from wild Rubus spp. in the Pacific Northwest. Despite its presence on native Rubus, G. idaeicola has not been seen in commercial blackberry fields. Recently, G. idaeicola was reported as the causal agent of canker, wilt, and death of blackberry in Serbia. Surveys of Oregon blackberry fields for G. idaeicola are on-going, along with research on the epidemiology and management of this emerging pathogen.