A Multi-Faceted Approach to Managing Powdery Mildew on Organic Table Grapes in Southwest Idaho

A Multi-Faceted Approach to Managing Powdery Mildew on Organic Table Grapes in Southwest Idaho

Summary

Work on this project began February 2008, as partners began selecting samples for evaluation for the overwintering fungus and choosing and marking vines to serve as sources for inoculum testing throughout the season. In March, producer Mike Medes began recommended preventative dormant sprays of sulfur compounds approved by OMRI. At this point Medes began ordering and constructing the adapted trellis systems, converting his existing “T” trellises to the recommended “Y” style.

Bud break occurred around May 6, at which time no fungus was detected within the buds. Partners have since learned that in Idaho, winter temperatures do not allow the fungus to overwinter inside the buds, which is common in California vineyards.

Throughout the spring and summer, Ariel Agenbroad and Tony McCammon kept in close contact with Medes and with Dr. Esmaeil Fallahi and Dr. Krishna Mohan, testing weekly or bi-weekly for presence of the fungus. Medes was kept extremely busy researching and following a prescribed preventative spray schedule, scouting the vineyard daily, and finishing the trellis adaptation. The vineyard was clean the entire season and the fungus was not detected visually or microscopically at any point. While this was a very good thing for Medes, it did not give partners a chance to implement the disease modeling tool or try any alternative treatment sprays except for compost tea.

In August 2008, Medes began harvesting and marketing clean, high quality Idaho table grapes to local, regional and international customers.

In September 2008, the project team held the first scheduled Field Day at Rocky Fence Vineyard. An introductory poster of the project and research objectives was presented, guests were served local and organic refreshments, and toured the vineyard. Medes led the group on a comprehensive overview of the practices and techniques implemented during the 2008 season and answered dozens of questions. Over 30 were in attendance. Response was very positive.

The introductory poster and handouts developed were also displayed in November at the Idaho horticulture Society Meetings in Nampa, Idaho, and again in February 2009 at the Sub-regional meeting of Western SARE in Spokane, WA.

• agenbroad_projectposter_2008.pdf
• Field Day and Vineyard Tour Handout.pdf

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