Grape leaves: Researchers study leaf removal technique | Business
TRAVERSE CITY – Michigan State University researchers are studying the effects of a viticulture technique on vines that can boost wine production in our state’s relatively cool climates. They work with Brys Estate Vineyard and Winery on the Old Mission Peninsula, which has been using the technology since 2014.
“I’ve been doing early leaf removal for a number of years,” says Coenraad Stassen, winemaker at Brys Estate.
Early leaf removal uses jets of compressed air to blow some leaves off the vines at the beginning of the season. Most growers, Stassen said, do the same thing late in the season – before draping the plants in nets to keep birds out – to give the fruits more light and speed up ripening.
Brys only removes the leaves in the 12 to 15 inch zone around the grapes at the start of the season, while allowing leaves higher up on the plant. The removal at the beginning of the season offers two advantages, Stassen said.
First, it deliberately causes heat stress on the plants by exposing the grapes to more sunlight and warmer temperatures. The added stress can cause the grapes to ripen earlier and produce more sugar. Second, removing it allows more air through the grapes throughout the summer, reducing the chance of mold, rot, and other problems.
“By removing the leaves early, you expose the fruit to the sun, but you also open the canopy,” said Stassen. “So if you get a lot of moisture, it helps prevent powdery mildew and downy mildew because you have airflow through the grapes.”
“The common rule of thumb is that you want five to 10 leaves above your fruiting area. Since our canopy is almost 3 meters high, we get at least 15 or 20 leaves above the fruit zone. “
“If you attack the cluster at the beginning of the season with high temperatures and lots of light, you will greatly improve the fruit quality,” Paolo Sabbatini, associate professor at Michigan State University’s Horticultural Institute, said in a press release. “The grapes ripen earlier, they have more sugar, they have more color, they all have the compounds that we like in wine.”
Michigan’s grape growing season runs roughly May through October. Breeders in California and the Mediterranean have longer growing seasons. A shorter season results in a higher likelihood of delayed fruit ripening, potential damage to the vines, and a limited time for grapes to ripen.
“Michigan really is a different place to grow grapes than any other place in the world,” said Sabbatini. “However, we have the potential to produce very outstanding wines. Unfortunately, the seasonal variability and the climatic challenges often limit this. “
Sabbatini, along with Ilce Medina Meza, Assistant Professor in the Department of Biosystems and Agricultural Engineering at MSU, is leading a $ 500,000 three-year project for the US Department of Agriculture’s National Institute of Food and Agriculture testing alternative canopy management strategies To support Michigan winemakers, grow grapes with high quality aroma, color, bitterness, and mouthfeel characteristics from the major red varieties grown in Michigan: Pinot Noir, Cabernet, and Merlot.
“I am very happy to have the research in our backyard and to receive immediate feedback,” said Stassen.
On-site research for the project will be conducted at the Brys Estate Winery in Traverse City. Samples of flowers, leaves and fruits from Brys Estate are returned to a laboratory where Medina Meza tests are analyzed to see the effects of early leaf removal on the compounds in the grapes. The aim of the project is to assess how early leaf removal affects the entire plant.
“This is a perfect project to show how important it is to work in an interdisciplinary manner. Paolo applies the farming practices while I work to understand more about the physiology of grapes, ”Medina Meza said in the press release. “It’s a great thing to bring different types of expertise together to see how the plants adapt or react to early leaf removal.”
Sabbatini said the early removal of the leaves is a variation of a classic cool climate winemaking technique used in northern Germany and New Zealand.
“Every year the producers see a new improvement, more yield in the field, they see more red wines as the end product,” said Medina Meza. “I think we’re making a huge impact in this regard, especially if this technique can be carried over to other cool climates around the world, including the rest of the American Midwest.”