In its 2020-21 fiscal year, the Oregon Wine Board of Directors granted $350,000 to researchers for eight projects with the potential to advance quality grape growing and winemaking in Oregon. The update below is part of a series to let you 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, 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 in Oregon vineyards: A pilot project on epidemiology and management

Project objectives:
In 2019, we initiated a project on grapevine trunk diseases (GTDs) with these objectives:

  • identify fungal pathogens associated with GTDs in Oregon;
  • understand if the different climatic regions in Oregon influence the spore dispersal of most common GTD pathogens; and
  • 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 with at least 16 different fungal pathogens reported based on samples submitted to the Oregon State University plant clinic. However, there is limited information on which GTDs are primarily found in Oregon vineyards, what their associated fungal pathogens are, and the distribution of these diseases.

Furthermore, it is unknown how Oregon’s climate impacts the occurrence of these pathogens. Different climatic regions provide unique opportunities for GTD pathogens that may require different methods of management.

Progress so far:
We surveyed 16 vineyards in Southern Oregon and 15 vineyards in the Willamette Walley. Vineyards were chosen based on a history of GTD and age of the vineyards.

The symptoms of each flagged vine were recorded. Some vines appeared to have stunted growth and/or yellowing or reddening leaves while other vines appeared healthy. Wood tissues were collected from all the flagged vines and stored at -80oC until further processing and DNA extraction. Samples from five vineyards have been cultured and DNA of samples from 18 vineyards have been extracted.

In order to determine the dynamics of spore release at two climatically distinct regions in Oregon, two spore traps were set up in vineyard blocks in the Willamette Valley and Southern Oregon. The spore trap collections have concluded and we are analyzing the traps that collected data for 15 months in both regions. Weather stations near the locations of the spore traps will also be analyzed in order to determine the correlation between weather variables and the quantity of spores trapped for most common fungal pathogens.

Next steps:
We initiated a GTD management trial with Trichoderma based biological product in early March 2021. Three treatments were tested in the older vineyard block in the Applegate Valley: 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). Data on Trichoderma colonization of the tissues and its effectiveness in reducing other fungal pathogens will be analyzed throughout 2021 growing season.