The following was written by John Scaduto, Rabun County Extension Coordinator, ANR Agent, and UGA Viticulture Extension Team member.
Thank you for the insight, John.
Research and experience has necessitated several manual labor tasks being performed in wine grape vineyards before the fruit ever reaches the winery. Of the major vineyard tasks during the growing season, many remain hands-on work, according to Duff Bevill, owner of Bevill Vineyard Management in Sonoma and Napa counties. An increasing number of vineyard tasks, combined with tight windows of opportunity to perform these tasks, have left vineyard managers wondering how to get it all done. In larger vineyards, this problem is compounded by and ever tightening labor pool.
Necessity is the mother of invention and mechanization in the agricultural industry, including the wine industry, has grown by leaps and bounds in the last decade. On a recent trip to Virginia for the 42nd annual American Society for Enology and Viticulture Conference the UGA Viticulture Team had the opportunity to see mechanized leaf removal equipment in action.
Canopy management has been the focus of many research projects over the past few years, including several projects being conducted by Dr. Hickey and the UGA Extension Viticulture Team in a couple vineyards in north Georgia. Researchers, and growers, are increasingly recognizing that grapes with greater sun exposure are often of higher wine quality potential and have less disease incidence and severity when compared to fruit grown deep in shaded canopies. All indications are that canopy management techniques, including leaf removal, are here to stay. This is particularly true in the variable cloudy, humid conditions experienced in Georgia and other eastern US grape and wine industries.
There are many manufacturers who make vineyard leaf removal equipment. Two popular brands are from the German manufacturer Clemens and the French company Pellenc. The Pellenc “soft touch” leaf puller (Figure 1) is the one we saw operated in a Virginia vineyard. The leaf puller uses a potentiometer as a position sensor to track the canopy and manage tool pressure. Sensors help the leaf puller’s drums follow the contours of the canopy to cut leaves whole. Many devices rely on the operator to position the leaf-removal tool as it moves down the canopy row and this increases the chance of uneven leaf removal.
Mechanized leaf removal equipment isn’t cheap. The leaf puller we saw comes as a front – mounted attachment for a standard tractor and runs in the neighborhood of $25,000. However, the feedback from the vineyard manager we talked with in Virginia indicates that the capital expenditure is justified by its tandem performance and ability to reduce manual labor costs.
Many growers in Oregon have shifted to mechanical leaf removal over the past few years because they say it can reduce costs. Estimates are that manual leaf removal costs approximately $270 per acre on relatively high-density vineyards (1,245 vines per acre) (Julian et al. 2008). Vierra (2005) reported mechanical leaf removal costs of $25 per acre compared to $130 per acre for manual leaf removal in moderate vine densities of 908 to 1,089 vines per acre in California’s Central Coast vineyards.
Reducing labor cost is an important issue, but there is also the issue of timing. The ability to remove fruit zone leaves from large acreages at a specific phonological stage (i.e. pre-bloom, immediately post-fruit set) is just not possible in some scenarios where the labor to acreage ratio is low. In these situations, leaf removal may start at bloom, but not finish until pea size berries/bunch closure, which is at the tail end of the critical stage for protecting grapes from fungal diseases. Take a minute and watch the video of the leaf remover in action (see link and disclaimer, at bottom of this post) and it becomes apparent that one operator with a tractor and a leaf removal attachment can cover a vineyard in the fraction of the time it would take a crew of skilled workers. In some commercial production scenarios, but not all, this may be a valuable tool.
As always, a word of caution before diving head first into the world of mechanical leaf removal. There are many ongoing studies regarding the efficacy of leaf removal, mechanical or manual, and there are many companies that offer this equipment. However, at this time, it looks like most leaf removal equipment is made for low-trained, vertically-shoot positioned vineyards. Thus, other training systems (i.e. high-wire positioned) might not benefit from such tools. Nonetheless, I was impressed by what I saw and thought it was worth sharing with our industry.
NOTE ON VIDEO: We are not promoting this dealer or manufacturer, nor suggesting that this piece of equipment is the best of its kind. It is the model we saw operated in Virginia and is simply a visual example of what a mechanical leaf remover can do. Other videos of mechanical leaf removal equipment can be found on the internet.
