Historic level of mildew affected Central Coast grapes in 2023 

California's wine grapes felt the impact of the flurry of atmospheric rivers that slammed the state in 2023.

"It was one of the highest mildew pressure records in the history of grape growing," Turrentine Brokerage's Central Coast Director of Grape Brokerage Audra Cooper told New Times.

Released Feb. 9, the brokerage's assessment of the state's preliminary 2023 Winegrape Crush Report revealed that mildew plagued varieties like pinot noir and chardonnay across California.

"Typically, it is very humid or wet conditions that sit on the grapes and cause mildew to grow," Cooper said. "It's not followed by high heat with winds to dry it out. Last year was a pretty wet year. We had a lot of rain late into the growing season as well, which is not typical."

She added that the potential of hurricanes on the Central Coast contributed to mildew formation on local grapes. While a hurricane didn't hit the Central Coast, the outside of the hurricane system still touched the area, increasing the regional mildew pressure.

Erin Amaral, managing partner at Pacific Coast Farming in Edna Valley, confirmed that she and her team noticed how an unusually cold growing season affected the grapes with powdery mildew.

"I mostly saw it in our white varietals," she said. "We saw powdery mildew in chardonnay and sauvignon blanc."

The grape crush report noted that Paso Robles, similar to many other wine grape-growing parts of California, witnessed an extended growing season resulting in the latest harvest in recent history. Usually, the harvest season in Edna Valley ends by October. But Amaral noticed a delay: The phenological development of the grapes was more than three weeks behind normal timing.

"My company got done [harvesting] just before Thanksgiving. I know others were still harvesting grapes right around Thanksgiving," she said. "The unusually cool growing weather caused an extended period of harvest."

The challenging weather also caused growers to underestimate their crops. The grape crush report stated that growers expected Paso Robles cabernet sauvignon vines to yield an average crop because of the weather. Instead, the weather proved to be ideal for berry sizing and resulted in a large crop of 95,085 tons. Amaral said this miscalculation also added to the late harvest.

"People were doing their estimates early," she said. "There are times where, in some cases, people have extra fruit on the vine to sell."

The 2023 harvest could have soared to the highest in Central Coast history if all the tonnage was picked, according to the report. A lot of grapes were left on the vine due to poor market demand. The total tons crushed last year rose by 23 percent, but stagnating case sales decreased demand for Central Coast grapes. In other words, bottled wine for retail didn't sell as much as in previous years.

However, the value of Central Coast grapes from Monterey, San Luis Obispo, and Santa Barbara counties rose by 27 percent for a total of more than $850 million.

"This increase in value can be attributed to the significant jump in yields over 2022, as well as the amount of grapes that were under multi-year contracts or sold during the active period of the market in the first half of 2023," Cooper wrote in the report.