California Winemakers No Longer Fight Drought—Now It’s Mildew

After years of drought conditions, California vintners are enjoying wetter conditions this year.
From cooler coastal regions experiencing an increase in a damp marine layer to Central Valley vineyards with more moisture than usual due to a very wet winter, growers and vineyard consultants alike are on the lookout for mildew.
"Quite rare for California."
Battany adds that warm and wet spring weather, following the earlier wet winter, has created perfect conditions for downy mildew in both counties.
Lawrence Sterling, director of operations at Iron Horse Vineyards in Sonoma County’s Green Valley, says the conditions for mildew are simple: "It loves moisture and lower temperatures, temps between 70° F to 85° F, and it stops when grapes reach about 18° Brix."
Sterling and other experts agree that prevention and early detection are the keys to any type of mildew management, with aggressive spraying and canopy management techniques leading the fight.
"In a year like this, we need applications even before bloom to keep mildew under control," said McGourty.
Dana Merrill, owner of Mesa Vineyard Management in San Luis Obispo, adds that growers can’t just use sprays.
Careful canopy management has the added advantage of appealing to growers and consumers who prefer to avoid spraying the vines and grapes.
But there are other fungicides, some even approved for use on organic crops, that can help control mildew outbreaks.

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