California Winegrape Research Articles

A variety-specific analysis of climate change effects on California winegrapes

California contains a broad geography over which climate conditions can be suitable for cultivating multiple varieties of winegrapes. However, climate change is projected to make winegrape cultivation more challenging across many of California’s winegrowing regions. In order to understand the potential effects of climate change on winegrapes, this study models variety-specific phenology for six winegrape varieties and quantifies the change in phenology and viticulturally-important agroclimate metrics over 12 of California’s American Viticultural Areas (AVAs) by the mid-21st century. Results show more rapid development for winegrapes with earlier budburst, flowering, veraison, and maturation across all varieties and AVAs. Cabernet Sauvignon shows the greatest change in phenology timing, while Chardonnay shows the least change. Likewise, the West Sonoma Coast AVA shows the greatest average change in phenology timing across varieties and development stages and Lodi AVA shows the least. Projected changes in agroclimatic metrics include an additional month of potentially damaging heat days (above 35 °C) in some AVAs, and decreases in frost days. These results have implications for numerous factors related to viticultural production, including water resources management and crop yield and quality, and underscore the need for California winegrape growers to improve their resilience to climate change by adopting strategies such as increasing soil health and water use efficiency and selecting cultivars suited for future climate conditions. By conducting climate effects analyses at the variety-specific and AVA scale, important information is provided to the winegrowing industry at a resolution that can support decision-making towards resilience.

Impacts of Climate Change in Baja California Winegrape Yield

We analyzed climate change scenarios and their possible impacts on winegrape yield in Baja California, the leading wine producer in Mexico. Linear regression models were used to predict the current yield based on climate and economic variables. Using future projections of the climate variables from two regional climate models (RegCM and RCA4), we evaluated the possible changes in yield for the Near Future (NF: 2021−2040) and Intermediate Future (IF: 2041−2060) periods under low (RCP2.6) and high (RCP8.5) greenhouse gas emissions scenarios. One regression model includes maximum and minimum temperatures (Tx and Tn) of the winegrape growing season and accumulated winter precipitation (Pre), and the other model also includes the real minimum wage and winegrape price to evaluate the operating cost paid by producers. The results show that the linear regression model with the climatic and economic variables explains 28% of the winegrape yield, and Tx and Tn had the greatest influence. The climate change scenarios show that during the winegrape growing season, these variables could increase more than 1 °C in the NF and more than 2 °C in the IF under the RCP8.5 scenario. These latter temperature changes could reduce the yield between 18% and 35% relative to the reference observed climate dataset (Livneh). However, winegrape yield is sensitive to economic factors, as the yield reduction increases at least 3% in all cases. Thus, adaptation strategies need to be implemented in the viticulture sector to reduce future impacts.

California wine grape growers need support to manage risks from wildfire and smoke

California has experienced an increase in the size and severity of wildfires in recent years, with wide-ranging impacts to agriculture. The 2020 wildfire season was particularly catastrophic, causing billions of dollars in damage to the state's world-renowned wine industry. Wine grape growers and wine producers statewide were recently surveyed to better understand the wildfire informational resources available to producers, as well as the role wildfire risk plays in operational management decisions. The survey results show that the negative impacts of wildfires on wine production may be the result of wildfire smoke more than of the actual wildfires. We also show that managers do not always make operational changes, even when they perceive increased wildfire risk. Despite diverse sources of wildfire-related information and operational guidance, there is not enough information to effectively manage fire risk.

Site characteristics determine the effectiveness of tillage and cover crops on the net ecosystem carbon balance in California vineyard agroecosystems.

Globally, wine grape vineyards cover approximately 7.4 M ha. The potential for carbon (C) storage in vineyards is of great interest to offset greenhouse gas emissions and mitigate the effects of climate change. Sustainable soil management practices such as cover crop adoption and reduced tillage may contribute to soil organic carbon (SOC) sequestration. However, site-specific factors such as soil texture, other soil physicochemical properties, and climate largely influence the range and rate to which SOC may be stored. To measure the potential for C storage in vineyards under varying sustainable soil management practices, we calculated the net ecosystem carbon balance (NECB) of three cover crops [perennial grass (Poa bulbosa hybrid cv. Oakville Blue); annual grass (barley, Hordeum vulgare); resident vegetation (natural weed population)] under conventional tillage (CT) and no-till (NT) management. Results provided evidence that vineyards served as C sinks. In sandy soils, the type of cover crop and tillage may be of little influence on the NECB. While in finer-textured soils, tillage reduced the NECB and higher biomass-producing cover crops enhanced the overall C storage potential of the vineyard agroecosystem. Overall, our results revealed that site characteristics, namely, soil texture and climate, were key determinants of the C storage potential of vineyards in Mediterranean climates such as those found in coastal and inland California wine grape production regions.

Vineyard-specific climate projections help growers manage risk and plan adaptation in the Paso Robles AVA

California's wine grape growers will face increasing challenges under a changing climate as most production occurs near the boundaries of current varieties' climatic thresholds. As part of this study, we developed a method for transforming downscaled climate information from the publicly available Cal-Adapt database into useful and useable climate projections for vineyard managers and advisors in the Paso Robles American Viticultural Area. We shared vineyard-specific projections during interviews of 20 managers and advisors. Overall, interviewees expressed trust in the projections and found them helpful in reducing their psychological distance from climate change. The projections prompted consideration of strategies for managing future climate risk and planning adaptation, with the majority of adaptations associated with long-term decisions such as row orientation, variety selection, dry farming, crop diversification and relocation. Agri-climatic decision support tools such as the one prototyped here may prove especially helpful for incorporating climate adaptation into the long-term business planning and vineyard redevelopment decisions facing managers and advisors in the near future. This approach could be extended to other California wine grape regions or to other perennial crops with expected vulnerabilities to climate change.

A “Sideways” Supply Response in California Winegrapes

AbstractThis paper explores growers’ supply response to the 2005 “Sideways effect” demand shock (Cuellar, Karnowsky, and Acosta, 2009) triggered by the 2004 release of the movie Sideways. We use a modified difference-in-difference approach to evaluate the supply response in California and regional supply response differences within California. We use U.S. Department of Agriculture data for the period 1999–2012 and find evidence of a supply response in the post-release period that is consistent with the “Sideways effect” on wine demand. The positive supply response for Pinot Noir is stronger than the negative response for Merlot and concentrated in lower value Central Valley vineyards. (JEL Classifications: D25, Q12)

Environmental values of California winegrape growers and the use of barn owl nest boxes as a tool for integrated pest management

Synthetic pesticides from agriculture pose threats to biodiversity, and the adoption of alternative pest management is vital to meet rising crop demands while protecting native species. For example, the use of nest boxes for barn owls (Tyto furcata and T. alba) may help control rodent pests and reduce the use of rodenticides. However, the environmental perceptions of farmers and how receptive they are to alternative pest management practices remains uncertain. Traditionally, agricultural policies and programs have focused largely on the economic self-interest of farmers, but these narrow approaches have proven insufficient to describe and predict conservation behaviors, and the study of environmental value orientations (EVOs) may better explain farmers’ adoption of novel wildlife-friendly practices. The study of EVOs can help identify people as “mutualists”, meaning those who value the environment for its own sake, and “utilitarians,” meaning those who value the environment for the services it can provide. We surveyed 71 California winegrape growers in order to better understand how their underlying environmental values relate to the use of barn owl boxes and other sustainable practices. Overall, most winegrape growers had mutualist value orientations (64%). However, there was a disconnect between the use of barn owl boxes and EVOs, with most respondents (80%) reporting the use of owl boxes regardless of underlying values. This opens the door for future research to examine whether this is true of other wildlife-friendly farming practices.

Impacts of global warming on southern California's winegrape climate suitability

Southern California has seen a resurgence of winegrowing regions in the past few decades, however the future of winegrape climatic suitability in the area has not been exhaustively explored. This study evaluated the future climate suitability for the cultivation of winegrape and potential global warming impacts on southern California's winegrowing regions through a series of high-resolution surface air temperature and precipitation projections obtained with the WRF-SSIB regional climate model. Results reveal that by mid-21st-century the surface air temperature will increase by approximately 1.2 °C, while average precipitation will decrease by as much as 11% in the southern winegrowing areas under the Intergovernmental Panel on Climate Change high greenhouse-gas emissions scenario. Evaluation of bioclimatic suitability indices indicate increases in heat accumulation for all major winegrowing areas; including an increase of about 10% in growing-degree day, while morning low temperatures in September may experience increases of approximately 11% in the future, thus impacting negatively the ripening stage of grapevines and leading to changes in wine composition and quality. Additionally, the extent of areas classified under the cool to warm climate suitability categories could decrease by nearly 42% in the study area by 2050. Conditions in southern California are already warm and dry for viticulture and continuing heat accumulation increase, along with rainfall reduction, could potentially place additional stress to winegrape crop in the area, including advanced phenological timing and moisture deficit stress that could lead to decreases in yield. The projected decline in viticulture suitability highlights the need for adaptive capacity within this sector to mitigate the impacts of global warming. Possible mitigating strategies include planting hotter climate grape varieties, moving vineyards to regions that are more suitable in the future, and adopting dry-farming techniques.

Virus surveys of commercial vineyards show value of planting certified vines

Viruses are of great concern in vineyards. They cost the California wine grape industry as much as $91,661 per acre over the life of a vineyard, according to a 2015 economic study of the North Coast wine-growing region. As a first step toward managing viruses, growers are encouraged to plant certified material regulated by the California Grapevine Registration and Certification program. There are risks in sourcing plant material from stocks that are not subject to the same level of regulation. We surveyed vineyards of varying ages for eight common viruses to demonstrate the value of selecting certified material for new plantings.

Long-Term Clinical Benefit to Anti-CCR4 Mogamulizumab: Results from the Phase 3 Mavoric Study in Previously Treated Cutaneous T-Cell Lymphoma (CTCL)

Long-Term Clinical Benefit to Anti-CCR4 Mogamulizumab: Results from the Phase 3 Mavoric Study in Previously Treated Cutaneous T-Cell Lymphoma (CTCL)

Anti-CCR4 Monoclonal Antibody, Mogamulizumab, Demonstrates Significant Improvement in PFS Compared to Vorinostat in Patients with Previously Treated Cutaneous T-Cell Lymphoma (CTCL): Results from the Phase III MAVORIC Study

Anti-CCR4 Monoclonal Antibody, Mogamulizumab, Demonstrates Significant Improvement in PFS Compared to Vorinostat in Patients with Previously Treated Cutaneous T-Cell Lymphoma (CTCL): Results from the Phase III MAVORIC Study

Preventative Disease Management and Grower Decision Making: A Case Study of California Wine-Grape Growers.

Preventative disease management is challenging to farmers because it requires paying immediate costs in the hopes of returning uncertain future benefits. Understanding farmer decision making about prevention has the potential to reduce disease incidence and minimize the need for more costly postinfection practices. For example, the grapevine trunk-disease complex (esca, Botryosphaeria dieback, Eutypa dieback, and Phomopsis dieback) significantly affects vineyard productivity and longevity. Given the chronic nature of the infections and inability to eradicate the fungal pathogens, the preventative practices of delayed pruning, applications of pruning-wound protectants, and double pruning (also known as prepruning) are the most effective means of management. We surveyed wine-grape growers in six regions of California on their use of these three practices. In spite of acknowledging the yield impacts of trunk diseases, a substantial number of respondents either choose not to use preventative practices or incorrectly adopted them in mature vineyards, too late in the disease cycle to be effective. Growers with more negative perceptions of cost efficacy were less likely to adopt preventative practices or were more likely to time adoption incorrectly in mature vineyards. In general, preventative management may require strong intervention in the form of policy or extension to motivate behavioral change.

Identifying economic hurdles to early adoption of preventative practices: The case of trunk diseases in California winegrape vineyards

Despite the high likelihood of infection and substantial yield losses from trunk diseases, many California practitioners wait to adopt field-tested, preventative practices (delayed pruning, double pruning, and application of pruning-wound protectants) until after disease symptoms appear in the vineyard at around 10 years old. We evaluate net benefits from adoption of these practices before symptoms appear in young Cabernet Sauvignon vineyards and after they become apparent in mature vineyards to identify economic hurdles to early adoption. We simulate winegrape production in select counties of California and find widespread benefits from early adoption, increasing vineyard profitable lifespans, in some cases, by close to 50%. However, hurdles may result from uncertainty about the cost and returns from adoption, labor constraints, long time lags in benefits from early adoption, growers’ perceived probabilities of infection, and their discount rate. Development of extension resources communicating benefits and potential hurdles to growers likely reduces uncertainty, increasing early adoption. Improvements in efficacy of preventative practices, perhaps by detecting when pathogen spores are released into the vineyard, will increase early adoption. Lastly, practice cost reductions will increase early adoption too, especially when the time it takes for adoption to payoff and infection uncertainty are influential in adoption decisions.

Multidimensional Responses to Disease Information: How Do Winegrape Growers React to Powdery Mildew Forecasts and To What Environmental Effect?

Access to better information can enable adjustments that improve individual and social outcomes. In agriculture, accurate forecasts can be especially valuable to both producers and society at large. We analyze the impact of disease forecasts on the responses of growers along multiple margins of adjustment. Using high‐resolution plot‐level panel data, we analyze how California winegrape growers adjust powdery mildew control strategies in response to disease forecasts. While trials that allow only treatment timing adjustments suggest these forecasts bring large environmental benefits, in practice many growers simultaneously adjust what, when, and how much they spray. We find that the net environmental impact of this multidimensional response may actually be negative.

Linking knowledge and action through mental models of sustainable agriculture.

Linking knowledge to action requires understanding how decision-makers conceptualize sustainability. This paper empirically analyzes farmer "mental models" of sustainability from three winegrape-growing regions of California where local extension programs have focused on sustainable agriculture. The mental models are represented as networks where sustainability concepts are nodes, and links are established when a farmer mentions two concepts in their stated definition of sustainability. The results suggest that winegrape grower mental models of sustainability are hierarchically structured, relatively similar across regions, and strongly linked to participation in extension programs and adoption of sustainable farm practices. We discuss the implications of our findings for the debate over the meaning of sustainability, and the role of local extension programs in managing knowledge systems.

The Welfare Impacts of Bird Damage and Its Control in California Wine Grape Production

AbstractWe developed a partial equilibrium model to examine the welfare impacts of bird damage and its control in California wine grape production. The model incorporates the impacts of pest damage and its control and allows the impacts to vary regionally. Importantly, the model requires minimal information to apply; only elasticities, current market price and production data, and information on the cost and effectiveness of the pest control methods are needed. We rely on data from a recent survey of California growers and use the model to estimate changes in wine grape prices, production levels, and consumer and producer surplus that result from both bird damage and its control in three grape-growing regions of California. Results suggest that eliminating the threat of bird damage and control costs results in an increase in producer and consumer surplus of 1.3% and 3%, respectively. Furthermore, eliminating current bird control and allowing any resulting damage would decrease producer and consumer surplus by 6.6% and 11.5%, respectively. (JEL Classifications: Q11, Q18, Q57)

Coordination of the California Winegrape Supply Chain

AbstractThis study investigates factors influencing coordination of the California grape and wine supply chain. Results corroborate prior findings that quality considerations and needs to protect investments in specialized or durable assets significantly increase usage of more formal coordination mechanisms, such as formal contracts and vertical integration or ownership. Consistent with findings for other industries, such investments are associated with greater contract complexity and inclusion of enforcement provisions, while trade partners' prior experience working together decreases contract complexity. Furthermore, our results suggest that quality considerations extend to greater use of formal contracts further downstream. (JEL Classifications: L1, L2, Q13)

Assessing the returns to R&D on perennial crops: the costs and benefits of Pierce's disease research in the California winegrape industry

Several complicating issues arise in evaluating the returns to research into varietal improvements for perennial crops compared with annual crops. We elucidate and address these issues in the context of a case study of research aiming to develop varieties that are resistant to Pierce's disease (PD) of grapevines. PD imposes costs of over $100 million per year on the California grape industry, even with public PD control programs in place. Research projects to develop PD resistant varieties of grapevines are at various stages of completion. We describe the economic problems posed by PD, document the research programs undertaken to address the disease and present an economic assessment of the returns to the investment, which are conditional on other policies. Using a simulation model of the market for California winegrapes, we estimate the benefits from research, development and adoption of PD‐resistant vines as ranging from $4 million to $129 million annually over a 50‐year horizon, depending on the length of the R&D lag and the rate of adoption. In addition to these specific quantitative results the paper offers insight into the broader question of economic evaluation of damage‐mitigation technology for perennial crops.

The Demand for California Wine Grapes

AbstractWine grapes contribute significantly to the economy of California, with a gross production value of more than $2 billion in 2010. Studies on economic issues in the industry require measures of demand response to price, but despite the economic importance of this industry, estimates of elasticities of demand for wine grapes have not been published. We use a flexible-form inverse demand system model to estimate elasticities of demand for wine grapes from three grape-growing regions in California, representing three different quality (price) categories. The resulting estimates of own-price elasticities are high, ranging from −2.6 for grapes in the low-price region to −9.5 for grapes in the high-price region. Such high elasticities are plausible given the role of international trade in wine, and they are consistent with synthetic estimates that we computed based on a combination of economic theory, data on market shares, estimates of some pertinent parameters in the literature, and informed guesstimates of values for other parameters. (JEL Classification: Q11, Q12, Q13)

Avian Conservation Practices Strengthen Ecosystem Services in California Vineyards

Insectivorous Western Bluebirds (Sialia mexicana) occupy vineyard nest boxes established by California winegrape growers who want to encourage avian conservation. Experimentally, the provision of available nest sites serves as an alternative to exclosure methods for isolating the potential ecosystem services provided by foraging birds. We compared the abundance and species richness of avian foragers and removal rates of sentinel prey in treatments with songbird nest boxes and controls without nest boxes. The average species richness of avian insectivores increased by over 50 percent compared to controls. Insectivorous bird density nearly quadrupled, primarily due to a tenfold increase in Western Bluebird abundance. In contrast, there was no significant difference in the abundance of omnivorous or granivorous bird species some of which opportunistically forage on grapes. In a sentinel prey experiment, 2.4 times more live beet armyworms (Spodoptera exigua) were removed in the nest box treatment than in the control. As an estimate of the maximum foraging services provided by insectivorous birds, we found that larval removal rates measured immediately below occupied boxes averaged 3.5 times greater than in the control. Consequently the presence of Western Bluebirds in vineyard nest boxes strengthened ecosystem services to winegrape growers, illustrating a benefit of agroecological conservation practices. Predator addition and sentinel prey experiments lack some disadvantages of predator exclusion experiments and were robust methodologies for detecting ecosystem services.