By Lauren Paterson, WSU College of Agricultural, Human, and Natural Resource Sciences

Grapevine red blotch disease spreads through vineyards and blotches leaves, shrinking wine and juice grape harvests.

Researchers at WSU’s Ste. Michelle Wine Estates Wine Science Center are studying how and why the grapevine red blotch virus, which causes the disease, spreads.

“We’re interested in finding out how the grapevines respond to the virus,” said Bhaskar Bondada, WSU associate professor.

Grape leaves work like solar panels, using sunlight to convert sugar into energy that fuels grape production.

Because leaves become less active when grapevines contract the red blotch virus, less sugar is moved through the plant, causing grapes to fade and grow more slowly. The virus also adversely affects pH, tannin levels, and other flavor characteristics of the fruit, and the final wine.

While virologists study the virus itself, Bondada, a physiologist, is interested in how the physical symptoms of the disease manifest on the plant.

“I’m studying what the symptoms look like in the plant on the cellular level, and how the virus spreads throughout the vine and the vineyard,” he said.

Research team member and WSU Viticulture & Enology graduate student Bailey Hallwachs took samples from multiple vineyards throughout Oregon and Washington over the summer, and is currently processing fruit and plant tissues samples at the Franceschi Microscopy and Imaging Center in Pullman. She uses microscopes to observe grapevine plant cells affected by the virus.

During the six years between her undergraduate and graduate studies, Hallwachs worked as an interior horticulturist at the Cheyenne Botanic Gardens, teaching gardening classes and managing the community gardens.

“Consistently, the issues we faced in production on a horticulture level were insects and diseases,” she said. “I wanted to get my graduate degree at WSU to understand the science behind solving major issues in agriculture so I could be part of the solution.”

The three-cornered alfalfa treehopper, a small green teardrop shaped insect, is the only confirmed insect to transmit the virus to the grapevine plant. There is currently no solution for treating grapevines infected with red blotch virus, aside from removing and replacing affected vines.

WSU’s research in red blotch virus is in partnership with Oregon State University. Field researchers at OSU provide the plant tissues and fruit, which are then analyzed at the WSU Wine Science Center.

“Our OSU partners are doing research in the field, and we are doing research at the physiological level,” Bondada said. “Once we have the data for them, we can develop more strategies to control the spread of the red blotch virus.” Research for this project is funded by the Oregon Wine Board and began in the spring. Bondada and Hallwachs intend to share their research in the new year.

By Lori Wollerman Nelson, ���سԹ�

A team at Washington State University Tri-Cities is researching the impact that a type of fungus could have on vineyard growth and associated nutrient uptake, which could lead to less watering and less fertilizer required for a successful grape crop.

Tanya Cheeke, assistant professor of biology, was awarded a $25,000 grant by the Washington State Grape and Wine Research Program to support a series of greenhouse experiments, as well as a two-year $40,000 grant to support a field experiment from the BIOAg program of the WSU Center for Sustaining Agriculture and Natural Resources.

Cheeke is working with graduate student KC Cifizzari and undergraduate Dylan Hartwig on the project specifically to understand the role that arbuscular mycorrhizal fungi, or AM fungi, play in plant nutrition and production for grapevines.

���سԹ� 85 percent of all plant species, including most crop plants, have an intimate relationship with AM fungi, Cheeke said. The naturally-occurring soil fungus forms a dense network of connections with the plant by inserting tiny threads, called hyphae, into its roots. Through this shared connection, the plant sends food to the fungus and the fungus increases water and nutrients available to the plant. AM fungi usually enhances plant nutrient uptake from the soil.

Cifizzari said they are including phosphorus treatments to see if the grapevines grown with AM fungi do just as well as plants that are only given fertilizer. If grapes grow as well with additional AM fungi and a lack of additional phosphorus as the grapes given only phosphorus, then adding AM fungi could reduce how much fertilizer vineyard managers need to apply to their vines, they said.

“The nice thing about AM fungi is that they are living organisms and the treatment should be self-renewing,” Cheeke said. “With fertilizers, you have to reapply regularly to get the same effect. That can be expensive.”

Merlot grapes are a popular varietal in Washington and were shown to respond more strongly as part of a greenhouse experiment by Cheeke and her team as compared to another varietal studied – Chardonnay.

Cheeke said the variability between varieties of crops is not uncommon, however, the researchers also caution that greenhouse conditions don’t necessarily mimic field conditions. Future research will investigate this further. A second greenhouse experiment to evaluate the effectiveness of different commercially-available AM fungi products is ongoing this fall.

“We will compare the growth of grape vines grown with three commercially-available AM fungi products, soil from a natural sagebrush habitat, and soil from a 50-year old vineyard,” Cheeke said.

The results of this study could help Cheeke know which AM fungi products to recommend to vineyard managers, if results prove successful.

Both Cheeke and Cifizzari are interested in the role that AM fungi could play in sustainable agriculture. Agricultural crops usually have reduced colonization of AM fungi because practices like applying fungicides and tilling the soil can deplete naturally-occurring sources of these fungi. Without their fungal helper, agricultural crops can require more water and fertilizer to be productive and can be more susceptible to plant diseases.

“Grape growers are very interested in the potential benefit of AM fungi, but they need more information to feel comfortable using it.” Cheeke said.

“Adding AM fungi to vineyard soils could be a way to make agriculture better for the health of the land and the people who work it,” Cifizzari said.

By Lauren Paterson, College of Agricultural, Human, and Natural Resource Sciences

Extreme heat, and too much water in response, affects a delicate balance in wine grape quality.

WSU researchers are studying the effects of heat, and developing an electronic, open-source cooling system to protect plants and wine quality, supported by the U.S and Washington State Departments of Ecology and recent grant awards from the U.S. and Washington State Departments of Agriculture and the Northwest Center for Small Fruits Research.

Markus Keller, professor of viticulture at WSU, is examining the effects of heat stress on grapes.

Heat causes physiological reactions in plants that affect growth rate and sugar content, and ultimately influence the flavor of wine.

“If grapes develop too rapidly, there will be too much sugar at harvest and too much alcohol in the wine,” Keller said. “Acidity also decreases with too much heat, making the wine taste bland.”

Vineyards that get too hot can also affect the color of the wine. To predict and prevent heat damage, WSU offers growers an online����(GDD) tool.

“We track temperatures and make the data available through GDD,” said Keller. The tool estimates growth and development of plants during the growing season by comparing average heat throughout regions of Washington.

Since 2011, when the GDD tool was launched, each growing season has been unseasonably warm.

“Every year, the average moves up a little,” Keller said. “It’s getting warmer.”

Evaporative cooling in vineyard canopies

Keller is now focusing on mitigating heat stress.

In his research, he discovered that fruit quality is more influenced by temperature than water.

“That was something unknown to us before,” he said, and runs against prevailing wisdom.

“When we water stress the plant, it grows less. It turns out, the effects of this water deficit in terms of fruit quality is really about temperature,” he said.

To avoid overwatering plants while keeping them cool amid heat waves, Keller and his team have developed a cooling system for vineyard canopies.

“Heat waves in Washington can reach temperatures of 110 degrees Fahrenheit or more,” said Ben-Min Chang, a doctoral candidate in WSU’s Department of Horticulture who works alongside Keller. “This is a very hot region.”

Over-watering in response to heat can cause plants to become oversaturated with water.

“It eventually penetrates to the soil and reaches the roots, which can cause excessive growth out of sync with the normal season,” Chang said.

Chang said the Cabernet Sauvignon grape, which usually has a complex flavor ranging from blackcurrant to cedar, might end up tasting like a green pepper. “That is a sign of excessive growth,” Chang said. “Growing grapes is a balancing act. Growers need to ensure their response to heat doesn’t tip the balance.”

Over the past two growing seasons, Chang developed a mechanized machine to lower the temperature of vineyard canopies.

He used a sensor from an infrared thermometer gun to read the temperature of the canopy, and an electronic micro-controller to activate misters installed throughout the vineyard.

“I use the micro-controller as the brain, and I use the infrared thermometer as the eye to measure the temperature,” Chang said. The device automatically runs the water misters when the canopy reaches 95 degrees Fahrenheit.

Using a sensor to measure water saturation on canopy leaves, Chang was able to improve his device. When the sensor detects that leaves have reached their saturation point, the mist stops.

To protect his sensors from ultraviolet rays, Chang uses a shiny aluminum wine can.

“Aluminum is a great reflector, so the sensor inside is protected,” he said.

The software that runs the electronic cooling system is open source. Chang plans to do the same with his canopy cooling device, so any grower can build their own.

“It’s a good way to pay it forward,” he said.

Following this season’s harvest, both Keller and Chang will see the results of their temperature control techniques.

In preliminary research, the team found that the evaporative cooling technique caused grapes to grow differently.

“The cooled grapes are already larger than the control group,” Chang said. While the control grapes take the brunt of the sun’s rays, those cooled with Chang’s device have fared better so far. Now comes the taste test.

“This experiment started in the vineyard and will end with us testing grapes and tasting the wine,” Chang said. “We’ll be able to see how the heat and evaporative cooling have affected the grapes and their overall quality.”

Wine-making normally takes four weeks after harvest, so Chang hopes to have more answers by the end of the year.

“We are thankful to the donors who allowed us to continue this important research,” Keller said. “We are hoping we can develop our cooling approach as a practical solution for growers and winemakers.

Preliminary research to be scaled into larger effort analyzing trends in wine industry entrepreneurship

By Maegan Murray, ���سԹ�

RICHLAND, Wash. – From renowned winemaking regions to those that aren’t typically known for winemaking, business faculty from Washington State University Tri-Cities are studying why people start wineries in locations across the United States.

Wine is currently made in every state in the nation; however, there are wineries located in regions that may not be suitable for grape growing or that don’t have a heavy foundation in wine entrepreneurship, said Rhonda Hammond, ���سԹ� assistant professor of hospitality business and wine beverage business management.

Study examines winemakers’ motivations

“There is a gap in data regarding entrepreneurship in the wine industry,” Hammond said. “There hasn’t been a lot of research conducted on wine entrepreneurship in the United States. Not all winemakers are established in the places best for winemaking.”

Hammond, Byron Marlowe, clinical assistant professor and wine and beverage business management program coordinator, and Paul Skilton, associate professor of management, want to understand winemakers’ motivations and analyze major themes in entrepreneurship for wineries across the industry

In spring 2017, the researchers examined 307 U.S. wineries and vineyards as identified by Wine America, the national association of American wineries. They analyzed web and other digital media information to determine why wine makers chose various winery locations, and to see if location impacted success.

Location familiarity may trump best growing climate��

Hammond said their initial research indicates some winery owners, especially for those in regions that aren’t known for wine, may have sought out locations based on familiarity, regardless of whether the region’s soil, atmosphere, reputation and other conditions were conducive for winemaking. Others may import their fruit juice from other locations, she said.

“If people are already familiar with a place, then it makes it easier for them to be aware of opportunities and feel more comfortable starting a business in that location,” she said. “Some may also be able to import grape juice. Just because they may not be able to grow the grapes there, doesn’t mean they won’t be able to get the juice to produce wine.”

Hammond said wineries located in climates unsuitable for grape growing may also make wine with other fruits.

“The definition of wine is fermented fruit juice,” Hammond said “Hawaii, for example, is making pineapple wine. With the ability to transport juices, winemakers can utilize materials from other regions.”

The researchers plan to expand their research into a more extensive study where they will reach out to wineries across the country to assemble in-depth information about the wineries’ beginnings.

“We are hoping this can give us some direction and hopefully turn into something much bigger for the betterment of the wine industry,” Hammond said.