October 7, 2013

Grapevine Diseases Costs Wine Grape Growers and State

Issues relating to various grapevine diseases, including Pierce’s Disease (PD), grapevine leafroll, and powdery mildew, are under scrutiny by Kate Binzen Fuller, a post-doctoral researcher in the Agricultural and Resource Economics Department at UC Davis, and colleagues.

Kate Fuller, post-doctoral researcher at UC Davis
The team’s PD research, a CDFA-funded effort, analyzes the costs of PD and associated control measures for grape growers and nurseries, and the benefits from state and federal programs that have been put in place to control its spread.  

“To understand the effects of PD in California requires an understanding of differences in disease characteristics and wine grape production characteristics in different parts of the state,” said Fuller. “In northern California, especially in Napa and Sonoma Counties, the Blue-Green Sharpshooter has spread the disease for many years, causing chronic but manageable damages. Wine grapes in Napa and Sonoma are typically very expensive and yield per acre is managed to be very low.”

“In southern California,” Fuller continued, “wine grapes are produced with much higher yields per acre and fetch much lower prices per ton, and the insect that spreads the disease is much more efficient at doing so. In Riverside County in particular, a non-native vector, the Glassy-Winged Sharpshooter (GWSS), decimated many acres of vineyard land in the late 1990s and early 2000s.

“As a result, the CDFA put programs in place in to prevent GWSS spread from southern California where the GWSS is now managed but endemic, to northern California’s high value wine regions,” stated Fuller.

“Our research suggests that PD of grapevines costs more than $100 million per year, even with public control programs in place that cost $50 million per year,” said Fuller. “This amount includes the costs of state and federal efforts to monitor and control the GWSS, research on PD/GWSS, and costs of compliance with the regulations by private firms including nurseries.”  

Fuller estimates that under the current program, PD costs wine grape growers and consumers $92 million annually. If the control program ended and the GWSS became widespread throughout California, the annual cost borne by growers and consumers could increase by as much as $185 million.

In additional research, Fuller and her colleagues estimate that benefits from research, development, and adoption of PD-resistant vines range from $4 million to $125 million annually over a 50-year horizon, depending on the length of the amount of time until these vines are available to growers, and the rate of adoption. The sooner the resistant vines are available and the more growers adopt them, the greater the benefit.