Preventative disease management and grower decision making: A case study of California wine-grape growers

Authors: HILLIS, VICKEN - University Of California; LUBELL, MARK - University Of California; KAPLAN, JONATHAN - California State University; Baumgartner, Kendra

Submitted to: Phytopathology
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 2/2/2017
Publication Date: 6/1/2017
Citation: Hillis, V., Lubell, M., Kaplan, J., Baumgartner, K. 2017. Preventative disease management and grower decision making: A case study of California wine-grape growers. Phytopathology. 107: 704-710.

Interpretive Summary: We examined the adoption and timing of a set of practices used to prevent grapevine trunk diseases, which cause severe yield losses if left unmanaged. Given the chronic nature of the wood infections and the fact that the pathogens cannot be eradicated once they infect a vine, preventative practices (delayed pruning, applications of pruning-wound protectants, and double pruning) are the most effective means of management. We surveyed wine-grape growers in six regions, in meetings organized by cooperative extension farm advisors and regional grower groups. Despite the fact that preventative practices have been shown to be effective, we found that a substantial number of growers do not adopt preventative practices, esp. given the widespread nature of trunk diseases. Furthermore, the majority that do so, adopt preventative practices in mature vineyards, which is after trunk diseases are present in the vineyard. We also found that growers with more negative perceptions of cost-efficacy were less likely to adopt preventative practices, and less likely to adopt them correctly in young vineyards. Because trunk diseases infect vines years before the symptoms appear, growers cannot easily test practices. This barrier to experiental learning through trial-and-error may facilitate development of negative cost-efficacy perceptions of preventative practices, in turn leading to low and incorrect usage. We argue that, in general, contexts in which prevention is needed and learning is constrained require strong intervention in the form of extension to motivate behavioral change.

Technical Abstract: We examined the adoption and timing of preventative grapevine trunk disease-management practices among agricultural decision-makers (growers) in California. These diseases (Botryosphaeria dieback, Esca, Eutypa dieback, Phomopsis dieback) significantly diminish vineyard productivity and longevity. Given the chronic nature of the wood infections and the fact that the pathogens cannot be eradicated, preventative practices (delayed pruning, applications of pruning-wound protectants, and double pruning) are the most effective means of management. We surveyed wine-grape growers in six regions, in order to examine their usage and perceptions of preventative practices. Despite the fact that preventative management practices have been shown to be effective, we found that a substantial number of growers do not adopt preventative practices, and that a majority of adopters incorrectly use them only in mature vineyards, too late in the disease cycle to be effective as preventative measures. We also found that growers with more negative perceptions of cost-efficacy were less likely to adopt preventative practices, and less likely to adopt them in young vineyards. We posit that individual and social learning are both constrained in this decision-making context, and that these barriers to learning facilitate development of negative cost-efficacy perceptions of preventative practices, in turn leading to low and incorrect usage. We argue that, in general, contexts in which prevention is needed and learning is constrained require strong intervention in the form of policy or extension to motivate behavioral change.