News

A grape virus causes vineyards to lose $60,000 per hectare, and there’s no defense against it

Red blotch disease alters the chemical composition and taste of critical winemaking grapes
Luyi Cheng
By Luyi Cheng
October 25, 2020

Alison Crowe knows there’s a problem.

Crowe is a winemaker in California’s Napa Valley. “If you drove through my vineyards right now, you’d see these cute little fuzzy leaves and tiny little baby grape clusters,” she said in April, when everything in the vineyards looked fine.

But around July and August, for some vineyards, red blotches appeared on grapevines’ leaves. The blotches signal infection, caused by a virus that stunts the sugar buildup in grapes and dramatically reduces the quality of wine. 

Over the past decade, winemakers like Crowe have watched as the disease — known as grapevine red blotch disease — spread across vineyards in the United States, devastating the country’s $162 billion grape industry. Scientists later discovered the virus spreads from vine to vine by the three-cornered alfalfa treehopper, an insect that feeds on grapes. Once infected, the value of grapes can decline more than $60,000 per hectare, yet growers have had no way to protect or treat infected vines.

Now, scientists, equipped with a multimillion dollar grant from the U.S. Department of Agriculture (USDA), are working with vineyards in California and Oregon to find answers for managing the disease and offsetting the economic losses of infected grapevines.

Leaves-720x540.jpg
Raul Girardello/UC Davis
A grape leaf without (left) and with (right) red blotch disease

“The end result is that we want to be able to develop sustainable management guidelines,” says Anita Oberholster, a wine chemist at University of California, Davis and the lead investigator of the grant. The $3 million research project led by Oberholster includes “collaborators of all the disciplines you need,” with scientists from institutions including UC Berkeley, Oregon State University, UC Riverside, University of Georgia, and the USDA working together to study the red blotch virus and its impacts.

Currently, without an effective treatment, winemakers’ only real option for infected grapevines is to pull them. Research suggests that if less than 30% of plants in a vineyard are infected, replacing them with “clean,” or uninfected, vines makes the most economic sense and minimizes losses. But for anything more than 30%, “it’s preferable to remove the entire block,” says Marc Fuchs, a virologist at Cornell University. “The virus moves like wildfire throughout the whole vineyard.”

While clearing out vines is logistically easy, according to Crowe — “You just get a big bulldozer in there” — it comes with a major economic blow. “You have to completely redo your vineyard infrastructure,” she explains. “You put a vine in the ground, and it will not produce grapes [right away], it’s a little baby.” To be ready for harvest again, the grapes will need another three to five years to grow and mature. That’s three to five years of lost profits.

“Early on, people were very frustrated,” says Cindy Kron, a pest management adviser for the University of California’s Division of Agriculture and Natural Resources. “And understandably so, because they would ask questions and we didn’t have answers.”

Red-blotch-disease-445x668.jpg
Kaylee Garrett on Unsplash
Red blotch disease is devastating for the country’s $162 billion grape industry

Oberholster’s recent research revealed how the virus affects the specific chemical composition of grapes to degrade the quality of the wine, and confirmed observations from growers that grapes were slower to ripen and lost sugar content when infected with the virus. Waiting a little longer to harvest the infected grapes and then dehydrating them can achieve the same sugar levels for producing wine, Oberholster’s research suggests. Trying to salvage the grapes by concentrating their sugar, however, still doesn’t make up for altering grapes’ chemicals known as phenolics, the compounds that give wine its color, mouthfeel, stringency, and bitterness. Oberholster hopes to continue testing wine processing steps that can balance out infected grapes’ chemical compositions to produce quality wine.

Kron also points out other research, such as her own, which aims to better understand the behavior of the treehoppers that carry the disease. Over two years, Kron recorded the seasonal cycle of the insects, such as when they arrived in vineyards, reproduced, and potentially transmitted the virus. This knowledge, Kron said, could help determine better timing for vineyard management decisions to reduce infection rates. Along with research showing which cover crops and weeds help the hoppers feed and reproduce, growers can use this information to design and test strategies to control insect populations, such as changing cover crops or pulling weeds before hoppers arrive at vineyards.

The infusion of USDA funds into the project means that studies can now span multiple years and cover multidisciplinary approaches. It also demonstrates how collaborative efforts and cooperation are necessary steps for solving complex agricultural problems. As the researchers continue to investigate pest control strategies and wine processing steps, Oberholster lays out their plans for the future. “Any of these practices that show potential, we will harvest, make wines, and really see — does it negate the quality impact?”

Crowe, now a winemaker for Plata Wine Partners, has spent the past 15 years making wines across Northern and Central California. She understands the importance of communication between growers, winemakers, and scientists, especially when dealing with red blotch disease. “It’s a problem that threatens our industry and we all need to work together to try to muddle through as best we can until we can find treatments or ways to mitigate it.”

This article is reprinted from Massive Science. Read the original here.

Luyi Cheng
Luyi Cheng

Luyi Cheng is a biology PhD student at Northwestern University working on understanding RNA structures and how they fold.

Join the ASBMB Today mailing list

Sign up to get updates on articles, interviews and events.

Latest in Science

Science highlights or most popular articles

Sphingolipids show potential as biomarkers for multiple sclerosis
Journal News

Sphingolipids show potential as biomarkers for multiple sclerosis

December 01, 2020

Maria Podbielska and colleagues at the Hirszfeld Institute write in the Journal of Lipid Research about their finding that ceramide levels vary in active and inactive MS lesions in the nervous system.

World AIDS Day 2020
Health Observance

World AIDS Day 2020

December 01, 2020

Despite decades of research and amazing scientific advancements, HIV remains a global threat.

Will the coronavirus evolve to be less deadly?
News

Will the coronavirus evolve to be less deadly?

November 29, 2020

All pandemics eventually run their course. But history and science suggest many possible pathways. How might COVID-19 end?

Uncovering details of molecular Ferris wheels inside cell structures
News

Uncovering details of molecular Ferris wheels inside cell structures

November 28, 2020

Simulations on the nation’s fastest supercomputer confirm details of a molecular mechanism that cell organelles use to regulate the pH of their environment.

The NIH is turning the human reference genome into a pangenome
News

The NIH is turning the human reference genome into a pangenome

November 26, 2020

In 2000, the human genome was announced as completed. But it was filled with gaps, and did not represent humanity’s genetic diversity. Read and watch a short film about recent updates.

From the journals: MCP
Journal News

From the journals: MCP

November 25, 2020

A destructive disease can lurk in a citrus plant’s vascular system. Misfolded proteins offer a key to inflammation in liver disease. And proteomic studies provide clues about signaling linked to neurological disorders.