The Napa County Winegrape Pest and Disease Control District’s purpose is to provide funding for the inspection, detection, prevention and education of Pierce's disease, with the goal of preventing the movement or spread of Glassy-winged Sharpshooter into Napa County and thereby preventing the spread of Pierce's disease by the insect. Currently, Napa County grower losses due to Pierce’s disease are in the millions of dollars annually—the introduction and establishment of the Glassy-winged Sharpshooter would multiply those losses many times.
In 2006, Napa County growers voted to expand the scope of the District to include programs to detect and control other potential winegrape pests.