CALIFORNIA AGRICULTURAL RESEARCH PRIORITIES PIERCE’S DISEASE
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COMMITTEE ON CALIFORNIA AGRICULTURAL RESEARCH PRIORITIES: PIERCE’S DISEASE
JAN E. LEACH, Chair,
Kansas State University, Manhattan
University of Maryland, College Park
MICHAEL J. DAVIS,
University of Florida, Homestead
DAVID G. HOEL,
Medical University of South Carolina, Charleston
L. JOE MOFFITT,
University of Massachusetts, Amherst
ALISON G. POWER,
Cornell University, Ithaca
TERRY L. ROOT,
Stanford University, Stanford
The Pennsylvania State University, University Park
WILLIAM E. SPLINTER,
University of Nebraska, Lincoln
BRIAN J. STASKAWICZ,
University of California, Berkeley
MARIE-ANNE VAN SLUYS,
University of São Paolo, Brazil
T. ULF WESTBLOM,
Central Texas Veterans Health Care System, Texas A&M University, Temple
KIM WADDELL, Study Director (through March 2004)
ROBIN SCHOEN, Senior Program Officer
MICHAEL KISIELEWSKI, Research Associate
DONNA WILKINSON, Research Intern
PETER ROGERS, Research Intern
CINDY LOCHHEAD, Project Assistant
JULIE COFFIN, Project Assistant
BOARD ON AGRICULTURE AND NATURAL RESOURCES
MAY BERENBAUM, Chair,
University of Illinois, Urbana
University of Illinois, Chicago
University of Wisconsin, Madison
H. H. CHENG,
University of Minnesota, St. Paul
W. R. (REG) GOMES,
University of California, Oakland
University of California, Riverside
PERRY R. HAGENSTEIN,
Institute for Forest Analysis, Planning, and Policy, Wayland, Massachusetts
Consumer Policy Institute/Consumers Union, Yonkers, New York
JANET C. KING,
Children’s Hospital Oakland Research Center, California
DANIEL P. LOUCKS,
Cornell University, Ithaca, New York
Cargill, Inc., Minneapolis, Minnesota
University of Guelph, Ontario, Canada
TERRY L. MEDLEY,
DuPont de Nemours & Co., Wilmington, Delaware
Ontario Veterinary College, Canada
Wellesley College, Massachusetts
ALICE N. PELL,
Cornell University, Ithaca, New York
Florida A&M University, Tallahassee
SHARRON S. QUISENBERRY,
Virgnia Polytechnic Institute and State University, Blacksburg
SONYA B. SALAMON,
University of Illinois at Urbana-Champaign
JACK WARD THOMAS,
University of Montana, Missoula
B. L. TURNER,
Clark University, Worcester, Massachusetts
JAW KAI WANG,
University of Hawaii, Manoa
CHARLOTTE KIRK BAER, Director
KAREN L. IMHOF, Administrative Assistant
This report represents the integrated efforts of many individuals. The committee thanks all those who shared their insight and knowledge to bring the document to fruition. We also thank all those who participated in our public sessions.
The committee is grateful to members of the National Research Council (NRC) staff who worked diligently to maintain progress and quality in its work.
This report has been reviewed in draft form by individuals chosen for their diverse perspectives and technical expertise, in accordance with procedures approved by the National Research Council’s Report Review Committee. The purpose of this independent review is to provide candid and critical comments that will assist the institution in making its published report as sound as possible and to ensure that the report meets institutional standards for objectivity, evidence, and responsiveness to the study charge. The review comments and draft manuscript remain confidential to protect the integrity of the deliberative process. We wish to thank the following individuals for their review of this report:
Paul E. Read, University of Nebraska, Lincoln
John S. Hartung, USDA-ARS, Beltsville, Maryland
Lori Ann Thrupp, Fetzer Vineyards
Donald L. Hopkins, University of Florida, Apopka
Carole Meredith (Emeritus), University of California, Davis
Gregory English-Loeb, Cornell University, Ithaca, New York
George W. Norton, Virginia Institute of Technology, Blacksburg
Jerome B. Siebert, University of California, Berkeley
Andrew J.G. Simpson, Ludwig Institute for Cancer Research, New York, New York
Ann Vidaver, University of Nebraska, Lincoln
Frank H. Stillinger, Princeton University, New Jersey
Although the reviewers listed above have provided many constructive comments and suggestions, they were not asked to endorse the conclusions or recommendations nor did they see the final draft of the report before its release. The review of this report was overseen by R. James Cook, Washington State University. Appointed by the National Research Council, they were responsible for making certain that an independent examination of this report was carried out in accordance with institutional procedures and that all review comments were carefully considered. Responsibility for the final content of this report rests entirely with the authoring committee and the institution.
Although Pierce’s disease (PD), caused by the bacterial pathogen Xylella fastidiosa (Xf), has been present in California vineyards for more than a century, it has not been considered a major problem for more than 40 years. The situation changed dramatically with the introduction of a new more aggressive vector, the glassy-winged sharpshooter (GWSS) Homalodisca coagulata (Say), a leafhopper of the Cicadellidae family. By the end of 2003, 15 counties in California were infested with this new vector, and in Riverside County alone PD damage estimates approached $13 million. Because of the high potential for GWSS to continue to move and transmit the pathogen within the state—and because of the tremendous value of grapes and grape products to California—this situation, understandably, created great concern. That worry is exacerbated by the facts that other strains of Xf can cause disease in other economically important crops, such as citrus and almond, and that GWSS is a voracious feeder, with tastes for a broad range of plants.
I can only imagine the frustration when this disease that historically had been confined to a relatively limited area of California first began to be spread farther and faster by the new vector. The old management strategies were insufficient by themselves, and it was not clear whether components of those strategies could provide some relief from the emerging problem, or whether entirely new paradigms for management of the disease and pest would be needed. Although pockets of solid and excellent research on PD, GWSS, and
their interactions with grapevine existed, none were sufficient to provide conclusive answers to those questions.
Faced with this crisis, the relevant industry, university, and government groups rapidly established a funding program that solicited the badly needed research. The initial net cast for research projects was very broad and inclusive. Now, with the accumulation of several years of data, the funding network has realized the need to review research progress and to focus efforts in areas that are most likely to lead to management of the PD–GWSS problem. Identifying research areas with the most promise was the major challenge presented to the Committee on California Agricultural Research Priorities: Pierces’ Disease, which has produced this report.
Although tragic in and of itself, the positive aspect of the PD–GWSS situation is that it calls attention to the need for models for coping with other emerging or introduced disease and pest problems of agronomic importance. Although the focus of the report is on PD–GWSS in grape in California, during its deliberations, the committee considered operational and research strategies in a much broader context. The intent is that the ideas and suggestions provided here will serve as a foundation for responses to future outbreaks.
Most of my career as a plant pathologist has been spent studying an annual crop species, where breeding for resistance is the most economically feasible and environmentally sound approach to disease management. Understanding the many complex facets of the PD–GWSS problem on grape was a particularly intriguing exercise. Breeding for resistance to PD in grapevine is not trivial for many reasons, not the least of which is the importance of the genetic identity of traditional cultivars used for wine making. The current social and political landscape in California restricts consideration of other options for disease management that might be acceptable elsewhere, including the use of transgenic varieties. These and many other considerations made for lively and thought-provoking discussions during committee meetings.
I particularly want to thank the committee members for their hard work in drafting, reviewing, and revising the document. It is particularly satisfying that the diverse expertise of the committee is positively reflected in the document, and I truly appreciate each member’s willingness to consider and discuss freely the perspectives of others. The PD–GWSS research community was particularly helpful to our deliberations; they patiently answered our many questions and frequently provided unpublished information for our education and consideration. Special thanks are extended to the staff of the Board on Agriculture and Natural Resources of The National Academies, including Michael Kisielewski, Donna Wilkinson, Julie Coffin, Cindy Lochhead, Peter Rodgers, and Tanja Pilzak. I thank Dr. Kim Waddell, the study director, for his essential scientific insights, his tremendous tact and patience, and his tireless efforts. Finally, I thank Robin Schoen, who, due to changes in staffing, was brought into the preparation of this report just before the review process. Her
Tables, Figures, and Boxes
Plant Diseases Caused by Different Strains of Xylella fastidiosa
Hypothetical Cost and Revenue Scenario of Vineyard Replacement
Estimated Vineyard Establishment and Replanting Cost
Grape Acreage by End Use, Citrus Acreage, Almond Acreage in California Counties, 2001
GWSS Distribution in California
Research Coordination through the Pierce’s Disease Control Program
Framework for Evaluating Research and Management Strategies
Who Should Implement Control Strategies?
Ensuring High Scientific Standards in Proposal Selection
Pathogen Effects on Vector Survivorship and Reproduction
Vector Attraction to Infected Plants
Implications for Epidemiology