Napa vineyards face new pest threat as infected vines traced to Costco sales

Napa Valley growers are being urged to track down potentially infected grapevines after agricultural officials discovered an invasive pest capable of spreading a devastating vine disease.

Napa Valley growers are confronting a fresh threat to vineyard health after local authorities warned that grapevines sold through retail giant Costco were found to be carrying the glassy-winged sharpshooter, an invasive insect capable of spreading a potentially lethal vine disease.

The Napa County Agricultural Commissioner has issued an urgent alert after discovering the pest in a batch of 220 grapevines sold locally. Officials fear the insect could spread Pierce’s disease, a bacterial infection that remains incurable and can eventually kill infected vines.

Search underway for remaining plants

According to Napa County Agricultural Commissioner Tracy Cleveland, only 63 of the affected vines have so far been located and destroyed.

Officials are now attempting to track down the remaining plants before the pest becomes established in local vineyards.

“GWSS is a devastating pest for our local vineyards, and it is critical for us to track down any potentially affected plants purchased at Costco or brought into Napa County,” Cleveland said.

“Vigilance and prompt reporting are essential.”

The infected vines originated from a single nursery, prompting concerns that additional plants may already have been distributed throughout the region.

A threat to vineyard survival

The glassy-winged sharpshooter transmits the bacterium responsible for Pierce’s disease, which attacks the vine’s water-conducting system.

As the disease progresses, vines gradually dry out and die, often requiring complete removal and replacement.

For vineyard owners, the financial implications can be severe. Replanting vineyards is expensive and replacement vines typically take several years before reaching full production.

The threat has prompted comparisons with phylloxera, the vineyard pest that devastated European vineyards during the late nineteenth century and forced widespread replanting across the continent.

Industry already under pressure

The warning comes at a difficult time for Napa producers.

As previously reported by the drinks business, wine producers in California and beyond are already facing weaker consumer demand, the growth of alcohol-free alternatives and reduced discretionary spending as inflation continues to weigh on household budgets.

Many producers have also been grappling with oversupply issues, while premium wine categories have faced slower growth in several key export markets.

Millions at stake

The California Department of Food and Agriculture operates an ongoing programme aimed at preventing the spread of the glassy-winged sharpshooter and controlling Pierce’s disease.

According to the department, those efforts help limit annual grower losses to around US$48 million.

Without existing control measures, losses would rise to an estimated US$104 million. Officials further estimate that an unchecked outbreak could cost growers an additional US$56 million each year through lost production and vine replacement costs.

For Napa growers already facing shifting consumer habits and economic headwinds, the emergence of another vineyard threat serves as a reminder that some of the industry’s biggest challenges still come from the vineyard itself.

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