- Homepage for the Wine Industry

California Winegrape Growers Reminded to Vote

Pierce's Disease Assessment Referendum Ballots in Mail This Week
by Ted Rieger
April 08, 2020

The California Department of Food and Agriculture (CDFA) expects to mail referendum ballots on April 9th to California winegrape growers to vote on whether or not to continue the assessment they have paid annually since 2001 to fund the CDFA Pierce’s Disease (PD)/Glassy-winged Sharpshooter (GWSS) Board’s programs. The 15-member Board advises CDFA on the use of assessment funds for research and outreach designed to prevent grapevine losses and control the spread of PD and its primary vector, the glassy-winged sharpshooter. Referendum approval will extend the assessment and Board five years, until March 1, 2026. Legislation requires grape growers to vote to continue the assessment every five years, which they have previously done three times (2005, 2010, and 2015). Legislation enacted in 2019 authorizing this year’s referendum, SB 449, was supported by the California Association of Winegrape Growers, Family Winemakers of California, and The Wine Institute. 

Program Activities and Successes

The PD/GWSS Board has invested $45.4 million since 2001 for research and outreach, with $34.3 million specifically for PD and GWSS research. This research has provided better understanding and knowledge about the GWSS as a vector, about the mechanisms of Pierce’s Disease development caused by the bacterium Xylella fastidiosa, and about disease resistance in grapevines. This research has enabled the development of new PD-resistant grapevine cultivars, and promising new methods and materials to prevent and combat PD.

Five new traditionally-bred winegrape varieties with PD-resistant genes that range from 94 to 97 percent Vitis vinifera parentage were developed by Dr. Andy Walker, viticulture professor and grape breeder at the University of California, Davis (UCD). They are being propagated at UCD Foundation Plant Services and will be available from certified grapevine nurseries. Additional sources and mechanisms of PD-resistance are being studied with the goal of breeding grapevines with multiple forms of genetic resistance for commercial use in the future.

Research by Dr. Steven Lindow of UC Berkeley on the endophytic bacterium Paraburkholderia phytofirmans shows great promise as a biological control for PD by its ability to colonize in grapevine xylem tissue and act like a vaccine to prevent the blockage of xylem tissue that occurs when PD infects and spreads within a grapevine. Lindow plans to conduct commercial scale tests over the next two years with vineyard applications of this bacterium as a foliar spray with a surfactant.

PD/GWSS Board research has evaluated chemical treatments and led to the establishment of effective treatment protocols for GWSS infestations and for managing GWSS insecticide resistance. Research has provided biological control strategies that include a program to breed and release parasitic wasps to reduce GWSS populations.

The majority of assessment revenue funds research, however, assessments alone do not fund all of California’s PD control activities. The statewide program is a partnership between industry and government. By paying the assessment, the wine industry demonstrates this program is important to support, and it enables industry investments to be leveraged with federal and state spending. Overall program funding supports County Agricultural Commissioner offices to maintain and monitor GWSS traps, oversee required nursery stock treatments, conduct nursery plant material shipment inspections at point-of-origin nurseries in GWSS-infested counties, and conduct destination inspections of nursery stock shipments in non-GWSS-infested counties.

Federal funding through the U.S. Department of Agriculture supports area-wide programs in California to control the spread of established GWSS infestations in Riverside, Kern, Tulare, Fresno and Madera Counties. These efforts effectively “hold the line” on GWSS in southern regions to prevent its spread north to other winegrape regions.  

Other Pests and Diseases

In 2009, legislation allowed the Board to designate other serious pests and diseases of winegrapes to receive assessment funds for research and outreach, provided these efforts do not seriously diminish efforts related to PD. The Board designated the European grapevine moth in 2010 and funded outreach to help lead to eventual eradication of this new pest that threatened North Coast vineyards. The Board has since designated the following pests and diseases: grapevine red blotch disease, the vine mealybug, the brown marmorated stink bug, grapevine leafroll disease, grapevine fanleaf disease, mealybug pests of winegrapes, and the spotted lanternfly.

The Board has allocated $6.3 million for research and outreach on other pests and diseases over the past 10 years. This research has improved understanding of the transmission and the effects of grapevine viruses, explored management practices for the brown marmorated stink bug and mealybugs, and is investigating grape cultivars and rootstocks for resistance to vine mealybug. The Board funded a multi-year project for grapevine virus management for the Lodi Winegrape Commission (LWC) for collaborative research and integrated outreach. The LWC has held outreach meetings free for growers statewide and is producing a series of written guides covering virus and mealybug best management practices.

Vote and Return Ballots by May 8th  

CDFA’s Marketing Branch conducts the referendum. All grape producer entities that paid the assessment on grapes crushed in 2019 will be mailed ballots, a total of approximately 4,000 eligible voters. Voters have until May 8th to return ballots. Results are expected to be announced in June. At least 40 percent of eligible voters must return ballots for the referendum to be valid. During the last referendum in 2015, over 80 percent of voters favored continuation of the assessment.

The Board sets the annual assessment rate, with a maximum of $3.00 per $1,000 of grape crush value.  The annual assessment rate has averaged $1.39 per $1,000 of grape value, and the most recent rate for 2019 was $1.00 per $1,000 of grape value. Assessment funds have provided nearly $70 million during the first 18 years of collection.

Information on PD Board activities, research, and news is available online at:

CDFA PD Control Program




Copyright© 1994-2021 by Wine Communications Group. All Rights Reserved. Copyright protection extends to all written material, graphics, backgrounds and layouts. None of this material may be reproduced for any reason without written permission of the Publisher. Wine Business Insider, Wine Business Monthly, Grower & Cellar News and Wine Market News are all trademarks of Wine Communications Group and will be protected to the fullest extent of the law.