In its 2021-22 fiscal year, the Oregon Wine Board of Directors granted $289,000 to researchers for six projects with the potential to advance quality grape growing and winemaking in Oregon. The update below is part of a series to let industry members know about the status of these projects.
Dr. Achala KC is an assistant professor of plant pathology in the Department of Botany and Plant Pathology at Oregon State University – Southern Oregon Research and Extension Center, specializing in tree fruit and wine grape pathology. She has prepared the update below.
Her co-investigator on this project is Dr. Jay Pscheidt, professor in the Department of Botany and Plant Pathology at OSU.
Grapevine Trunk Diseases (GTDs) in Oregon Vineyards: A Pilot Project on Epidemiology and Management
- Identify fungal pathogens associated with GTDs in Oregon.
- Understand if different climatic regions in Oregon influence spore dispersal of most common GTD pathogens.
- Compare different cultural practices while pruning to minimize availability of primary spores.
Importance to the Oregon wine community:
There is evidence of GTDs in Oregon; however, there is limited information on which GTDs are primarily present in Oregon vineyards and how we prioritize management practices. Based on this study, Botryosphaeria dieback and Esca diseases were the most commonly present diseases. We detected these and other GTDs in younger vineyards as well, which is crucial in undertaking preventative management practices against these diseases as early as possible. We also identified that under favorable weather conditions, the maximum spore release of Botryosphaeriaceae spp. in Oregon vineyards occurs between early December and early February. This information is critical in determining pruning dates under rainy winter conditions and necessitates pruning wound treatments if pruning occurs within these timeframes.
Progress so far:
In 2019, we initiated a project on grapevine trunk diseases (GTDs) in which we surveyed 15 vineyards in southern Oregon and 14 vineyards in the Willamette Valley for possible GTD symptoms and sample collection. Fungal species were identified through culture and PCR-based methods. Through culturing, isolated fungi that are associated with GTD were identified in 21% of the surveyed vineyards. These fungi were Seimatosporium lichenicola, Pestalotiopsis sp., Truncatella angustata, Hormonema viticola, and Hormonema sp. Through PCR Phaeoacremonium spp., and Phaeomoniella chlamydospora, which are associated with Esca and Petri disease, were detected in 21 and 7% of the surveyed vineyards, respectively. Botryosphaeriaceae spp., which are associated with Botryosphaeria dieback, were detected in 52% of the surveyed vineyards. PCR to detect Eutypa lata, Eutypella vitis, and Cylindrocarpon spp., did not result in any positive tests. Botryosphaeriaceae spp. were the most commonly detected species and their spore release were affected by the region. In the Willamette Valley, the spore detection occurred between December and February. In southern Oregon, the detection occurred between November and January.
We initiated a GTD management trial with a Trichoderma-based biological product in early March 2021. Three treatments including 1) complete removal of vine prunings from the vineyard; 2) Leave the prunings in the alleyway then mechanically mow with a flail mower; and 3) Leave the prunings in the alleyway, mechanically mow, and spray with Bio-Tam (both wound and soil application) were tested in the older vineyard block in the Applegate Valley. We collected brush samples and wound samples to analyze Trichoderma colonization of the tissues and longevity of protection until ten weeks. However, we did not detect any of the Trichoderma spp. after two weeks of application in any of the tissue samples. This was a one-year field trial and the results indicated that Trichoderma efficacy may depend on various factors including temperature and moisture conditions at the time of application, rate and/or times the product is applied per season. Nonetheless, this study requires further confirmation with multiple years of study at different climates.
More research on disease management strategies targeting these diseases under different climatic conditions is essential to provide effective disease management recommendations.