priorities and needs, and will assist the state in coordinating with national and international program efforts to address the disease.

In this report, the committee recommends ways to improve the development and implementation of a coherent research and management agenda to address Pierce’s disease. Chapter 2 discusses the issue of setting research priorities and the process of selecting the best science, emphasizing the need for economic analysis to enable more thoughtful decision-making. Chapters 3, 4, and 5 examine potential research and management approaches for protecting plants from the disease and for controlling the pathogen, Xylella fastidiosa (Xf) and its insect vector, the glassy-winged sharpshooter (Homalodisca coagulata [Say], GWSS). The remainder of Chapter 1 provides an introduction to the biology of the disease and the vector and offers estimates of the costs of their management. The chapter concludes with an overview of the organizational and institutional stakeholders who are responding to the threat of the disease and with a brief discussion of factors that could directly or indirectly influence the feasibility or effectiveness of proposed management strategies.

PIERCE’S DISEASE

In 1892, Newton B. Pierce, California’s first trained plant pathologist, characterized a disease that had been called “Anaheim disease” or “mysterious vine disease” that now bears his name. PD is caused by (Xf), a bacterial plant pathogen. Once transmitted to a plant by an insect vector, the bacteria multiply and generate a plaquelike substance within the xylem of the plant. Ultimately, water movement is blocked, and the plant dies.

Pierce’s (1892) bulletin for the U.S. Bureau of Agriculture, The California Vine Disease, became the first comprehensive published description of the disease, which had caused significant problems for California agriculture up to that point and has continued to do so ever since: Between 1884 and 1900, PD destroyed more than 35,000 acres of grapevines in the Los Angeles basin (Gardner and Hweitt, 194). By 1921, the disease had become endemic throughout most of the grape-growing areas of California (Hewitt, 1970). It was observed in the Napa Valley in 1887, in the Livermore area in 1888, in the Sacramento and Santa Clara valleys in 1900, and in the San Joaquin Valley in 1921. Three major epidemics occurred in the twentieth century: Between 1914 and 1918, vineyards in the Santa Clara Valley were devastated. Then, between 1935 and 1940, more than 50,000 acres of grapevines in the San Joaquin and Napa valleys were destroyed (Gardner and Wewitt, 1974). The last major epidemic occurred in the Napa Valley between 1960 and 1962.

Twentieth-century PD epidemics renewed interest in research. Throughout much of the century, PD generally was believed to be caused by a virus (Hewitt et. al., 1949) because no bacterial or fungal pathogens had been identified and because PD was known to be transmissible by grafting (Hewitt,



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