Location: Crops Pathology and Genetics ResearchTitle: Managing grapevine trunk diseases in California’s southern San Joaquin Valley
|HILLIS, VICKEN - Boise State University|
|LUBELL, MARK - University Of California|
|KAPLAN, JONATHAN - California State University|
Submitted to: American Journal of Enology and Viticulture
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 1/22/2019
Publication Date: 7/7/2019
Citation: Baumgartner, K., Hillis, V., Lubell, M., Kaplan, J. 2019. Managing grapevine trunk diseases in California’s southern San Joaquin Valley. American Journal of Enology and Viticulture. 70:267-276. https://doi.org/10.5344/ajev.2019.18075.
Interpretive Summary: Every California vineyard eventually is attacked by grapevine trunk diseases (Esca, and Botryosphaeria-, Eutypa- and Phomopsis diebacks). Wood infections by the causal pathogens cannot be eradicated without costly removal and retraining (a technique known as ‘vine surgery’). Diseased vines produce less and less fruit, and either die or are removed due to lack of profit. Field trials by researchers have shown less infection with preventative practices, but past surveys of wine-grape growers showed limited adoption. To help convince growers to adopt preventative practice, outreach materials we developed, with help from extension agents and grower groups, depict the long-term economic benefits of adoption in young, healthy vineyards, before symptoms appear. However, not all practices used for wine grapes are practical for other grape-production systems, planted with genetically distinct cultivars and trellised/ trained differently. A survey of table and raisin-grape growers in California’s southern San Joaquin Valley revealed their usage and perceptions of two preventative practices: delayed pruning and pruning-wound protectants. Economic analyses simulated the economic benefits of adopting such practices in the table-grape cultivar ‘Crimson Seedless’, comparing adoption in a young, healthy vineyard (years 3 and 5) versus in a mature, diseased vineyard (year 10). A cost-effective timing for vine surgery, in combination with preventative practices, was also analyzed. In spite of acknowledging the presence of trunk diseases and yield losses in their vineyards, 70% of growers use neither preventative practice. Among the few who use a practice, more than 50% adopt in mature vineyards, thereby missing the benefits of earlier adoption. Although vine surgery is costly, adopting this practice before year 14 is cost-effective. Our findings reveal the need for outreach programs targeted to separate grape-production systems, highlighting trunk-diseases management practices that are uniquely suited to their horticultural and labor-supply constraints on the timing of pruning.
Technical Abstract: Most California vineyards are eventually attacked by one or more grapevine trunk diseases (Esca or Botryosphaeria-, Eutypa- and Phomopsis diebacks). These fungal pathogens cause chronic infections of the wood, which are slow to develop. The symptoms that follow can take years to become obvious. Prevention is an efficient approach, but requires adoption before symptoms appear. To encourage early adoption of preventative practices, economic analyses simulated their benefits in the table grape cultivar Crimson Seedless. Adoption of delayed pruning or pruning-wound protectants was compared in a young, healthy vineyard (years 3 and 5) versus in a mature, diseased vineyard (year 10). A survey of table and raisin grape growers in California’s southern San Joaquin Valley revealed their usage and perceptions of preventative practices. Also, to help growers with mature vineyards, the economic benefits of vine surgery (also referred to as “trunk renewal”) between years 11 and 15 were examined. Our economic simulations showed prevention is cost-effective, if adopted in young vineyards. However, in spite of acknowledging the impact of trunk diseases, only 25 to 30% of growers use preventative practices, and only half of such growers adopt in young vineyards. Further, growers who use prevention and adopt early also perceive preventative practices as more cost-effective. Therefore, an outreach strategy to convince non-adopters must emphasize the long-term economic benefits of early adoption of preventative practices, given the inevitable appearance of symptoms at vineyard maturity. Despite the high one-time cost of vine surgery, our economic analyses suggest its adoption is a cost-effective complement to prevention, and thus, it should be integrated into management recommendations for table grape vineyards at 11 to 15 yrs.