Red blotch disease alters the chemical composition and taste of critical winemaking grapes
By: Luyi Cheng
October 16th, 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.
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