Vintners, growers, industry groups and researchers work together proactively to monitor and manage potential threats from a variety of pests and disease.

Below is a listing of common pests and disease that can affect grapevines:

European Grapevine Moth

The European Grapevine Moth (EGVM) is an invasive moth, that when left to its own devices will infest grape clusters and can cause significant damage. Since its first appearance in 2009, the Napa County Agricultural Commissioner’s office, and industry partners such as the Napa Valley Vintners, have worked extensively to educate growers and vintners about quarantine and eradication measures for this pest. Learn about eradication efforts.

Pierce’s Disease

The Glassywinged Sharpshooter and Blue Green Sharpshooter are vectors for a bacterial disease called Pierce’s Disease, which has the ability to kill a grapevine in 2-3 years and for which there is no known cure. In order to prevent the spread of this harmful disease, vintners and growers work proactively to monitor for the pests and report and remove any diseased vines. Learn more about Pierce’s Disease.

Leafroll Disease

Grapevine leafroll viruses are a classification of viruses that limit the flow of nutrients and water within a grapevine and cause stunted growth and the rolling and yellowing or reddening of grape leaves. The virus is transmitted by diseased budwood and vine mealybugs, making it critical for vintners and growers to source wood from reputable non-diseased sources and to monitor mealybug populations. Although not a widespread problem in Napa, industry groups and researchers work together to prevent the further transmission of leafroll in Napa’s vineyards. Read UC Davis’ description of Leafroll Disease.

Red Blotch

Red blotch describes the symptoms of a newly discovered grapevine virus that appears to be very similar to leafroll, but is genetically different. Researchers are working to quickly identify possible vectors. In the meantime, Napa vintners and growers are working with nurseries to ensure that diseased materials are not planted in the Napa Valley. Read UC Davis’ description of Red Blotch.


Known as the insect that has caused the most widespread damage to the world’s grapevines, including the Napa Valley, phylloxera was first introduced to California’s vines from European cuttings. Because the pest was an unknown, many of Napa’s vineyards were planted to a rootstock that was the perfect host for the pest, resulting in widespread damage. Today, phylloxera resistant rootstocks are planted widely in the Napa Valley, making the threat of damage much less likely.

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