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The vine mealybug, a pest that poses a serious new threat to the California grape industry and efforts to reduce pesticide use, was found for the first time this summer in the San Joaquin Valley, according to Walter Bentley, University of California integrated pest management entomologist.

Bentley will explain how farmers can help prevent the spread of vine mealybug and how to identify the pest at the San Joaquin Valley Grape Symposium, 9 a.m. to 12 noon Wednesday, Dec. 9, at the C.P.D.E.S. Hall, 172 W. Jefferson Ave., in Easton. Registration is $6 for the meeting and proceedings, $16 to include lunch.

The vine mealybug’s first confirmed find in the United States came four years ago in Southern California’s Coachella Valley. It was identified in a tablegrape vineyard south of Arvin in June 1998 and 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.

"If the vine mealybug spreads in California, it will be a very serious problem," Bentley said. "And everybody expects it to spread."

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.

"In those areas, the vine mealybugs would just take off," Bentley said. "And they are already having difficulty controlling two other mealybugs."

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.

"This pest could ruin our IPM program," said Bentley, who, as a member of UC’s Statewide Integrated Pest Management Project, works with a team of advisors based at the UC Kearney Agricultural Center near Parlier to promote the use of ecologically sound pest management practices in California agriculture. "And the only materials we have that control the pest are coming under the gun from the Food Quality Protection Act."

Also to be covered at the San Joaquin Valley Grape Symposium are: Managing Spider Mites in Vineyards, Dried-on-the-Vine Raisin Update, Principles of Canopy Management, and Grapevine Identification. The keynote speaker is Vaughn Koligian, Chief Executive Officer for the Raisin Bargaining Asociation, who will discuss the new marketing order for California raisins.

For more information about the symposium, contact Bill Peacock at (559) 733-6458, wlpeacock@ucdavis.edu, or Don Luvisi at (805) 868-6223, daluvisi@ucdavis.edu.