—story and photos by Kate Prengaman
—Illustration by TJ Mullinax
Where do growers go for good information on managing difficult problems?
University extension, of course. Trusted consultants and suppliers, probably. And hopefully the pages of Good Fruit Grower. But growers who hear from their neighbors about practice changes are the most likely to make changes themselves.
That’s not news — farmers may be the original influencers in this regard — but extension specialists are trying to measure this effect and harness it to help grape growers battle grapevine leafroll and red blotch diseases.
“It just takes one or two people to say, ‘I’ll try that.’ Then, they share what they are finding, and peer influence seems to catalyze other people to start using the technology,” said Monica Cooper, viticulture advisor for the University of California’s Cooperative Extension in Napa County.
The technology, in this case, is pheromone mating disruption for vine mealybug, the primary vector of Grapevine leafroll-associated virus 3 in California.
In Washington, leafroll spreads through a different vector, the grape mealybug, and researchers are still testing mating disruption with a pheromone that is in the registration process. But the ability to use mating disruption to control mealybugs could be the tool Washington growers need to launch a coordinated campaign against the virus.
“Coordinated” being the operative word: Multiple studies in other systems have shown that mating disruption works best under areawide management.
Cooper will speak about the adoption of mating disruption for mealybugs and the role grower collaboration played in that effort in Napa County at the Washington Advancements in Viticulture and Enology, or WAVE, seminar hosted by the Washington State Wine Commission and Washington State University on April 23.
Science of communication
Pests don’t care about boundaries. So, neighbors can benefit by doing the same.
“Grower cooperation comes as a theme through all the work that I have done,” Cooper said. “It started with vine mealybug, the first seriously invasive pest in my career.”
While the initial response to the pest involved fear, frustration and looking for someone to blame, growers eventually came to see that they had a common enemy, she said. The need to coordinate a response to the next pest on the scene, the European grapevine moth, further solidified collaborations.
Observing the importance of coordinated pest management in Napa County vineyards, Cooper leaned in, tapping research associate Malcolm Hobbs to further study the social science of how growers incorporate new scientific evidence into their management. Facilitating network-based communication is now a key part of Cooper’s and Hobbs’ extension work.
“Most people don’t just have one person who gives them advice. They like to triangulate and check around with their network,” she said. “As extension, we’re not the only people who can build up expertise in the community.”
Today, much of Hobbs’ work focuses on how growers put knowledge about disease management into action.
“There’s a whole literature on how to get farmers to adopt new practices,” he said. “Most growers know how to control vine mealybug and how leafroll is spread. The trick, now, is the individual vineyards still need to work together to do mating disruption and coordinate roguing, so it’s still a collaboration to get people to work with their neighbors. One of the problems is that it can be quite a sensitive conversation.”
For example, with a neighbor you don’t know, asking if they have infected vines can be a tricky topic to broach; likewise when a viticulturist or vineyard manager needs to communicate the urgency about an infected block to a winemaker or owner.
“Viticulturists are hired because they know about the biology, but they’ve got to advocate to the owners,” Hobbs said.
Those challenges require a different skill set — more communication than viticulture. To help the industry have those conversations, Hobbs and Cooper launched a series of communication workshops this year with a leadership coach to help people run through scenarios, like starting a conversation with a neighbor or boss. It differs from a usual extension workshop, Hobbs said, but so far has been received very well.
His research shows that well-connected individuals with solid communication skills can impact how knowledge and practice changes spread. Hobbs uses an approach called social network analysis to chart how information moves through the Napa industry. In that analysis, he can track the impact of the industry’s neighborhood action groups to coordinate the response to red blotch, the top threat to Napa vineyards today.
“When you create these neighborhood groups, the network appears to become denser and information goes around faster,” he said, citing the leaders of the groups as key nodes in the webs of communication.
The neighborhood group approach began as a leafroll response; the groups were integral in getting that disease under control, Cooper said. Now as the Napa industry grapples with red blotch — a virus transmitted by insects for which they don’t have mating disruption — it remains an important way to share knowledge and connect people to discuss sensitive issues.
“What we found in group meetings is that people talk generally, but sometimes it’s conversation between two growers that needs to happen,” Cooper said.
Washington takes notes
Several years ago, WSU Extension viticulturist Michelle Moyer teamed up with Cooper and Hobbs for a survey-based study of how growers make disease management decisions. They found that while extension talks and media articles spread awareness of an issue, practice change stems from growers’ own networks.
In that light, the Washington State Wine Commission funded Moyer and WSU Extension specialist Gwen Hoheisel to prepare a roadmap for areawide leafroll management and to outline paths that could help the industry adopt mealybug mating disruption when the technology becomes commercially available.
“We’re trying to educate our growers ahead of time, so we can be ready,” said Melissa Hansen, research director for the commission.
For insect-transmitted diseases, areawide management approaches work best. “You can manage your block, but if your neighbor is not, it can still move the virus into your block,” Moyer said.
Of course, that concept is not new.
“There are books and books on areawide management successes and failures,” Hoheisel said. “We tried to synthesize that for the commission and make a specific application for leafroll.”
Growers have access to readily available information about how to manage grapevine leafroll disease, she said, but they need economic motivation to embrace costly management practice change.
“If the goal is to achieve little to no spread of the grape leafroll disease, then you need better control of both the vector and the virus,” said Hoheisel. While there are many strategies growers could deploy today to reduce the spread of leafroll disease, without that viable vector control, growers in Washington lack an economic incentive to do the rouging, she said.
The key findings from the research into other areawide programs show success stems from grower coordination and an economic incentive to change.
“It’s not top-down,” Moyer said. “It really takes growers, within their communities, talking with each other.” •
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