Project Title: Evaluating the Impacts of Early Fruit-Zone Leaf Removal in Red Wine Grape Varieties
Project Duration: FY15, FY16, and FY17 (July 2014-June 2017)

Principal Investigator(s): Michelle Moyer, Assistant Professor
Organization: WSU-IAREC, 24106 N. Bunn Rd., Prosser, WA 99350
Telephone: 509-786-9234

Cooperator(s): Jim Harbertson
Organization: WSU – Wine Science Center
Description of Participation: Dr. Harbertson’s lab performed most wine analyses and winemaking for the project.

Cooperator(s): Devon Newhouse
Organization: Newhouse Farms Inc, Sunnyside, WA
Description of Participation: Mr. Newhouse donated the use of his land, labor in operating the mechanical leaf remover and harvest equipment, and the fruit for winemaking for the entire duration of the project.

Project Summary: A completed project report will be provided at the end of the funding period, as not all aspects of the project are complete at this time.

Properly managing a grapevine canopy is a true test in understanding grapevine development and response to inputs. While recent studies on early fruit-zone leaf removal (i.e., pre-bunch closure) are providing interesting and optimistic results, most of the work is being done in cooler climates (Palliotti et al. 2011, Tardaguila et al. 2010). Our past research has shown that early fruit-zone leaf removal is a viable option in white wine grapes in eastern Washington (Komm and Moyer 2015). Will we see similar beneficial results in red grape varieties, where the target goals of “quality” center on sugar, anthocyanins, and tannins? Early fruit-zone leaf removal has also been shown to reduce under-ripe flavors in red wine varietals (i.e., reduction of methoxypyrazines) (Scheiner et al. 2010). In addition, the nature of the canopy microclimate can influence the incidence and severity of many economically significant grape diseases, including powdery mildew (PM) and Botrytis bunch rot (BBR). In particular, fruit-zone leaf removal is a commonly recommended cultural practice for disease control in organic vineyards (i.e., vineyards with limited effective chemical options) as it alters canopy microclimate (temperature and moisture), which is a significant factor in the development of the fungi associated with PM and BBR (Carroll and Wilcox 2003, Delp 1954, Nair and Allen 1993, Thomas et al. 1987).

Various field-based methods were used to evaluate the objectives of this project. This included a replicated field trial at a commercial site with different timing of leaf removal implemented in two different varieties (Cabernet Sauvignon, Merlot). The fruit from this trial was then used to make associated wine and conduct wine sensory. In objectives relating to fungicide evaluation, a research block at WSU-IAREC was used to conduct the trial, where unsprayed controls were maintained to guarantee disease pressure.

This project aimed to develop a better understanding of the impact of early fruit-zone leaf removal on red grape cultivars, how manual and mechanical leaf removal may differ in how these impacts are realized, and how leaf removal can interact with fungicide programs to enhance or detract from disease management. This project was also designed to see how early fruit-zone leaf removal influences components associated with high-quality red wine: anthocyanin and tannin accumulation.

Read more by downloading the full report above.

Pest & Disease // Viticulture //