A new pest poses a serious new threat to California's grape industry and efforts to reduce pesticide use. The vine mealybug was found this past summer in the San Joaquin Valley.

“If the vine mealybug spreads in California, it will be a very serious problem,” says Walter Bentley, UC integrated pest management entomologist.” And everybody expects it to spread.”

As the vine mealybug feeds on vines and grape stems it produces tremendous amounts of sticky honeydew, promoting sooty mold and rendering the grapes inedible. It also transmits grape viruses. To date, scientists in the United States and other parts of the world have not been successful controlling the pest with its natural enemies.

The vine mealybug was first found in the United States 4 years ago in the Coachella Valley. It was identified in a tablegrape vineyard south of Arvin in June 1998. Since then small populations have been detected at two other nearby vineyards. A native of the Black Sea area and an established pest of grapes, date palms and figs in South Africa, Egypt, India and Israel, the vine mealybug is a separate, and much more damaging, species than the grape mealybug already found in the San Joaquin Valley.

Since the pest prefers warmer, non-freezing areas, Bentley said the renowned wine producing vineyards of Napa, Mendocino and Sonoma counties, plus those in the mild Central Coast counties of San Luis Obispo and Monterey are threatened by the possible spread of vine mealybug.