The Threat

A Lethal Threat to California Winegrapes

Pierce’s disease (PD) is a lethal disease of grapevines and a serious threat to California’s thriving winegrape industry. The disease is caused by Xylella fastidiosa (Xf), a bacterial pathogen that has been present in California for more than a century. While many insects can spread Xf, the establishment and spread of the glassy-winged sharpshooter (GWSS) in California in the 1980s and 1990s created a new and serious threat of significant statewide damage. At risk is California’s grape and wine industry, which generates annual economic activity of $57.6 billion within the state and $114 billion nationally.

Slowing the Spread

The Pierce’s Disease Control Program (PDCP) was established in 2000 to slow the spread of GWSS and minimize the statewide impact of PD while solutions are being developed. The program's operational approach relies on five major components: contain the spread, statewide survey and detection, rapid response, outreach, and research. Read more about PDCP’s work in the Annual Report to the Legislature.

Pierce's disease costs more than $100 million per year, even with public control programs in place. If the PDCP ended, and GWSS was distributed freely throughout California, the annual cost to the winegrape industry would increase by more than $185 million. Read more about The Costs and Benefits of Pierce's Disease Research in the California Wine Industry.


The PDCP collaborates with several agencies and cooperators to implement this statewide strategy, including:

  • United States Department of Agriculture

  • California county agricultural commissioners

  • University of California

  • Pierce’s Disease and Glassy-winged Sharpshooter Board

  • Pierce’s Disease Advisory Task Force

  • California winegrape growers

Finding Solutions

California winegrape growers came together in 2000 to lobby for an assessment to raise funds earmarked for research on PD and GWSS. This was signed into California state law in 2001, and the Pierce’s Disease and Glassy-Winged Sharpshooter Board was created to direct those funds. Read about the progress made against pests and diseases threatening California's vineyards in "20 Years of Progress – Research, Innovation, Action."


Thanks to statewide containment and management efforts funded by federal, state, and local government and the grower assessment, GWSS has largely been prevented from spreading to new areas. This has given researchers time to search for long-term, sustainable solutions to PD and GWSS, supported by funds collected via the grower assessment. By sharing responsibility and resources, this partnership effectively addresses the pest and disease challenges facing California winegrape growers.

California Department of Food and Agricu