Summary
Among all cultivated woody perennials, grapevines are known to be infected with the largest number of plant viruses—more than 100 viruses belonging to 21 different families or having similarity to unclassified plant satellite viruses have been reported on Vitis germplasm worldwide. Two of these viruses, grapevine leafroll-associated virus 3 (GLRaV-3) and grapevine red blotch virus (GRBV), are considered the primary causal agents of economically important diseases occurring in California and other grape-growing regions: grapevine leafroll disease (GLD) and grapevine red blotch disease (GRBD).
In 2022, the California Department of Food and Agriculture (CDFA) requested the National Academies of Sciences, Engineering, and Medicine to provide guidance to the CDFA Pierce’s Disease/Glassy-Winged Sharpshooter (PD/GWSS) Board by convening an ad hoc committee that would conduct three interrelated activities addressing research on GLRaV-3 and GRBV. Activity 1 (Review of Proposals Submitted to CDFA PD/GWSS Board) and Activity 2 (Critique of CDFA PD/GWSS Board’s Request for Proposals [RFP] and Proposal Selection Process) were completed in 2023. This report addresses Activity 3 (see Box S-1).
The committee addressed its task using information gathered from various sources, including published papers, presentations and discussions at webinars and public meetings, and documents provided by CDFA. Based on this information and its deliberations, the committee developed conclusions and recommendations for the consideration of the CDFA PD/GWSS Board and other parties involved in addressing GLD and GRBD. Selected
BOX S-1
Statement of Task for Activity 3: Review of Current Knowledge on Grapevine Viruses, GRBV and GLRaV-3 Research Outcomes/Gaps and Future Research Approach
The committee will review the state of knowledge about the grapevine red blotch virus (GRBV) and grapevine leafroll associated virus type 3 (GLRaV-3) and the management of diseases they are associated with and develop guidance to the PD/GWSS Board in its efforts to support research that leads to a reduction in the spread of GRBV- and GLRaV-3-associated diseases and their economic impacts.
The committee will examine the scientific literature and gather information from experts, plant health practitioners, and grape growers. The committee will explore recent and current research activities on GRBV and GLRaV-3 and their insect vectors that are funded by the CDFA PD/GWSS Board.
In its review, the committee will identify the following as they relate to GRBV and GLRaV-3:
- The most significant knowledge gaps in the current understanding of grapevine red blotch disease and grapevine leafroll disease epidemiology;
- Research areas where significant progress has been/has not been achieved;
- Research areas that may yield the most promising short- and long-term management solutions;
- New genetic tools and research platforms that could be used to study grapevine viruses;
- Opportunities for collaborative research that could accelerate progress in finding grapevine disease management solutions;
- Other viral pathogen systems (animal and human) that could provide insights or additional research directions; and
- Opportunities to improve the current CDFA PD/GWSS Board’s research review and funding process, and opportunities to draw from a wider range of researchers across various disciplines and fund a wider range of national researchers.
The committee will prepare a consensus report with conclusions from its review, describing what is currently known about GRBV and GLRaV-3; what knowledge is needed to improve management of the diseases caused by these viruses; and the committee’s recommendations with respect to a viable approach for supporting research on grapevine viruses.
conclusions and recommendations are highlighted in this summary (see Boxes S-2, S-3, and S-4); full conclusions and recommendations are detailed in the report chapters and in Appendix C.
CURRENT KNOWLEDGE ON GLD AND GRBD AND THEIR ASSOCIATED VIRUSES AND VECTORS
GLD and GRBD occur in red or black- and white-fruited grapevine cultivars, but foliar symptoms vary by cultivar, are less pronounced in white-fruited cultivars, and could be confused with the symptoms of nutritional disorders and other maladies. Because the two diseases cannot be reliably distinguished based on visual inspection alone, definitive diagnosis relies on the detection of GLRaVs and GRBV in the laboratory using nucleic acid-based methods (GLRaVs and GRBV) and serological assays (GLRaVs). Current knowledge about the viruses associated with these diseases and their insect vectors is summarized in Table S-1.
TABLE S-1 Current Knowledge about the Viruses Associated with GLD and GRBD and Their Insect Vectors
| Disease | GRBD | GLD |
|---|---|---|
| Associated virus(es) | GRBV | GLRaV-1, -2, -3, -4, -7, -13 |
| Virus characteristics | Belongs to genus Grablovirus, family Geminiviridae; members of this family encode their genetic information on a circular genome of single-stranded DNA | GLRaVs belong to three genera in the family Closteroviridae; they are composed of monopartite, positive-sense, single-stranded, polycistronic RNA genomes. GLRaVs differ in their genome lengths and in the number and arrangements of their encoded genes |
| Insect vectors | Primary insect vector: Three-cornered alfalfa hopper (TCAH; Membracidae); additional insect vectors suspected | Principal vectors of concern (worldwide and in California): Mealybugs (Pseudococcidae) Minor vectors: Soft scales (Coccidae) |
| Mode of virus transmission: Circulative and non-propagative; requires an extended acquisition access period before transmission occurs | Mode of virus transmission: Semi-persistent; transmission takes place within a 1-hour acquisition access period and a subsequent 1-hour inoculation access period; no latency period between virus acquisition and transmission | |
| Host range: Wide; Asteraceae (feeding hosts), Fabaceae (principal breeding hosts) Vitis spp. are occasional feeding hosts | ||
| Impact on grapevine | Interferes with foliar metabolism and metabolite translocation; reduces yield, total soluble solids, and anthocyanin accumulation; alters grape ripening | Reduces grape yield, juice and wine quality, and the productive lifespan of affected vineyards; disrupts photosynthesis and carbohydrate metabolism in symptomatic leaves |
KNOWLEDGE GAPS
During the course of the study, the committee identified numerous knowledge gaps, and those that need to be addressed sooner are presented in Box S-2 (see Chapter 4 of this report for a full discussion of the knowledge gaps). Box S-2 also contains the high- and medium-priority research recommendations for addressing knowledge gaps (labeled HP for high priority and MP for medium priority). Research recommended in Chapter 4 would generate information needed for further research and development of other control methods, tools, or strategies.
BOX S-2
Research to Address Knowledge Gaps to Help with Developing Promising Short- and Long-Term Solutions
GLD Biology, Virus-Host Interactions, and Host Defense Mechanisms
It is generally understood that there is a causal relationship between the presence of GLRaVs and the stronger expression of GLD symptoms in response to GLD in red or black-fruited grapevine cultivars compared with white-fruited cultivars. The reasons underlying these differences have not been well elucidated. Several knowledge gaps also exist regarding the interactions between GLRaVs and their hosts and host defense mechanisms.
Despite decades of research, knowledge on the genetic and phenotypic complexity of GLD-associated viruses remains limited. Fundamental studies using synthetic biology approaches can be applied to systematically investigate how different GLRaV genotypes influence disease outcomes (Conclusions 4-1, 4-2).
Recommendation 4-1: Support research to generate more information about GLRaV-3 genetic variants that could help guide GLD management.
Recommendation 4-2 (HP): Support foundational research to understand the intrinsic and extrinsic factors contributing to the efficient spread of GLRaV-3, including interactions with other vitiviruses.
Knowledge of the factors required for GLRaV-3 infection and resistance in Vitis hosts could create opportunities for developing novel control strategies, but these factors have not been elucidated and the role of non-coding RNAs in grapevine and GLRaV-3 genomes in infection or symptom development also remains unexplored. Further investigations into the extent of GLRaV-3 host range may also generate valuable information that could be exploited for GLD management (Conclusions 4-3, 4-4, 4-5).
Recommendation 4-3 (MP): Support research to identify host factors required for GLRaV-3 infection and resistance in Vitis hosts and to investigate the role of non-coding regions of grapevine and GLRaV-3 genomes in infection and symptom development.
Recommendation 4-4: Support research to examine the common and unique responses of red or black- and white-fruited wine grape cultivars to GLRaV-3.
GRBD Biology, Virus-Host Interactions, and Host Defense Mechanisms
GRBV isolates are classified as one of two genetic variants, clade 1 or clade 2. Currently, there is scant evidence regarding the differences between clades in terms of symptom expression, efficiency of transmission by TCAH, or the selection pressures acting on GRBV populations (Conclusion 4-6). Also unknown are any synergistic effects resulting from GRBV co-infection with other viruses, or how mixed infections with other viruses might affect the expression of GRBD symptoms or GRBV fitness.
Recommendation 4-5: Support studies to advance understanding of the epidemiological consequences of GRBV genetic diversity and interactions with other viruses.
There are still gaps in the understanding of the function of the GRBV genome with regard to specific roles of GRBV proteins in plant cells. To date, virions have not been observed in GRBV-infected plants using microscopy, and the lack of a tractable model host that becomes systemically infected with GRBV limits the study of virus gene functions and virus-host interactions (Conclusions 4-7, 4-8).
Recommendation 4-6 (MP): Support research to determine optimal model hosts (e.g., Pixie grapevine and/or herbaceous hosts) to facilitate the study of molecular GRBV-plant interactions and direct research efforts to transfer this knowledge to wine grape cultivars.
Current knowledge about latency and incubation periods after GRBV inoculation, which may vary among grapevine cultivars and under different environmental conditions, is insufficient to inform GRBD management recommendations (Conclusion 4-9).
Recommendation 4-7 (HP): Support research to elucidate latency periods in different cultivars and rootstock-scion combinations, including the time from virus inoculation until vector acquisition, time until symptom expression, and time until the virus is detectable in plant and/or vector tissues.
Effects of Mixed Infections, Environmental Factors, and Rootstock-Scion Interactions
Grapevines can be simultaneously infected with multiple viruses, but how mixed infections affect disease severity and evolution of GLRaVs and GRBV (or GLD and GRBD) has not been thoroughly investigated. The effects of changing climatic conditions and other factors that modulate disease cycles including temperature, humidity, carbon dioxide, ozone, drought, and vineyard management practices on virus-vector-host interactions have not been determined (Conclusions 4-10, 4-11).
Recommendation 4-8: Support research on the effect of mixed infections on GLRaV and GRBV evolution and the diseases they cause, as well as research on the effects of environmental factors, grapevine management practices, and changing climatic conditions on GLD and GRBD virus-vector-host interactions and epidemiology. Industry trends and stakeholder input could be used as a guide for prioritizing scion-rootstock combinations to use in experiments.
A variety of factors, including the scion cultivar, genetic background of rootstock, rootstock-scion interactions, virus profile in individual grafted vines, synergistic interactions between co-infecting viruses, and environmental conditions, could contribute to the presence and severity of symptoms from GLD and GRBD. Resistant rootstocks along with other control strategies could help to mitigate negative effects of viral diseases in vineyards (Conclusions 4-12, 4-13).
Recommendation 4-9 (MP): Support research on the presence and diversity of viral resistance in grapevine rootstocks with different genetic backgrounds in order to inform the incorporation of resistant rootstocks into virus control strategies.
Recommendation 4-10: Support research to determine the contribution of planting with infected, non-certified vines on virus spread.
Diagnostics and Detection
The lack of affordable diagnostic methods for on-site detection delays timely disease diagnosis and management efforts, allowing the continued spread of GLRaVs and GRBV. There is a need for additional affordable diagnostic tools that can detect GLRaV-3 and GRBV infections early and are suitable for extensive use in commercial vineyards (Conclusion 4-14).
Recommendation 4-11 (HP): Support research to develop new, simple, and affordable high-throughput tests for GLRaV-3 and GRBV.
Research to profile plant responses to GLRaV-3 and GRBV (and their vectors) may reveal unique volatile organic compound (VOC) profiles that could establish a basis for the development of hand-held electronic noses or differential mobility spectrometry devices for pathogen detection in the field (Conclusion 4-16).
Recommendation 4-12: Support research to identify VOCs unique to GLRaV-3 and GRBV infection or relevant vector infestations and determine the detection efficiency of VOC-based methods compared with other diagnostic tools.
Remote sensing technology has the potential for remote or in-field diagnosis of GLD and GRBD in individual vines; however, testing the efficacy of this approach will require scalable deployment of remote sensing devices for detection of infected vines in a large-scale area (Conclusion 4-17).
Recommendation 4-13 (HP): Support studies on the use of remote sensing technology to facilitate large-scale and early detection of GLD and GRBD in various tissues of commercial cultivars (including white-fruited cultivars) to increase the reliability, specificity, and sensitivity of detection with this technology.
As GLRaV-3 and GRBV continue to evolve in vineyards and non-crop habitats, nucleic acid-based assays used for virus detection will need to be upgraded to enable reliable detection of newly emerged virus variants (Conclusion 4-20).
Recommendation 4-14: Support research to determine the feasibility of using rolling circle amplification or other single-stranded circular DNA detection techniques to help detect GRBV at very low concentrations and for universal GRBV detection.
Recommendation 4-15 (HP): Support research for detecting GLRaV-3 and GRBV with nucleic acid-based methods that can be used in the field at large scales.
Currently, the costs associated with sample collection, preparation, and analysis restrict testing to levels that may not be effective for diagnosing and monitoring virus infected grapevines. Consensus is lacking on the most effective sampling technique and minimum sample size for accurately estimating GLRaV-3
and GRBV prevalence across different vineyard settings, regions, and nursery increase blocks (Conclusion 4-21).
Recommendation 4-16 (HP): Support research evaluating optimal sampling methods and minimum sample size for accurate estimation of GLRaV-3 and GRBV prevalence in vineyards to inform the development of best practices for adopting new technologies and for integrating multiple detection methods to improve accuracy and scale (i.e., using both molecular methods and remote sensing technology).
Standardization and verification by an independent organization(s) are important for enhancing the robustness and reproducibility of diagnostic protocols. To date, laboratory protocols for diagnostic testing of GLRaVs and GRBV have not been standardized (Conclusion 4-23).
Recommendation 4-17 (HP): Support efforts to develop standardized GLRaV-3 and GRBV diagnostic testing protocols that, once verified and certified, could be adopted by all laboratories that provide testing services for nurseries and commercial vineyards.
Vectors
While there are reports about potential additional insect vectors of GRBV, there has not been definitive evidence that other insects in addition to TCAH can transmit GRBV to grapevines (Conclusion 4-25).
Recommendation 4-19 (MP): Support research to identify additional vectors of GRBV using rigorous experimental approaches.
There are gaps in the understanding of GLRaV-3 transmission, particularly about the role of different vector species and their distribution in California; the mechanisms of GLRaV-3 acquisition and transmission; the transmission efficiency of diverse GLRaV-3 isolates; the acquisition, retention, and inoculation periods of all vector species; and how environmental factors influence GLRaV-3 transmission dynamics (Conclusion 4-26).
Recommendation 4-20 (HP): Support research on the mechanisms and timing of acquisition, retention, and transmission of all GLRaV vector species, as well as the influence of environmental conditions and host genotype on GLRaV transmission dynamics.
Additional knowledge gaps for GLRaVs and GRBV include the mechanisms of virus-vector interactions, the effect of the environment on epidemiology, and
how mixed infections with multiple viruses might impact transmission. The time required to acquire and transmit these viruses has been examined, but virus localization in the vectors has not been confirmed, and the precise viral retention sites have not been thoroughly characterized; knowledge of these factors would improve understanding of the mode of transmission for GLRaV-3 and GRBV. In addition, the roles of vector endosymbionts, genes, proteins, and metabolites mediating transmission have not been studied for GLRaVs or GRBV; this information is needed to understand transmission dynamics and to develop novel tools for disrupting transmission for the management of GLD (Conclusions 4-27, 4-28).
Recommendation 4-21: Support studies to identify interactions between GLRaVs and GRBV and their vectors that are required for transmission, as well as studies to identify genes, proteins, and metabolites involved in virus transmission to develop control strategies based on interference of virus-vector interactions.
Vector Plant Preference and Behavior Manipulation by GLRaVs and GRBV
GLRaV-3 and GRBV have only been reported to occur on Vitis and noncultivated grapevines, but the relative contributions of different host species or varieties in GLRaV-3 or GRBV spread are not known and comprehensive studies to understand host plant utilization and preferences of vectors have not been completed. In addition, vector behavior might change in response to plant infection by GLRaV-3 and GRBV 3 (i.e., changes in insect behavior mediated through the host plant), which may affect the settling, feeding, fitness, and dispersal behavior of the vectors (Conclusions 4-29, 4-30, 4-31).
Recommendation 4-22 (MP): Support research on virus-vector-host interactions to determine how the different species or varieties of Vitis and non-cultivated grapevines contribute to virus spread, as well as how GLRaV-3 or GRBV infection of the host can alter vector behavior.
Recommendation 4-23 (MP): Support research to broaden the understanding of complex interactions among the virus, vector, and host to enable the development of models of disease spread and strategies to prevent disease transmission.
There are major knowledge gaps regarding TCAH overwintering behavior, seasonal GRBV spread to grapevines, and differences among distinct grapevine-growing regions in California. Population models may help predict TCAH generation development associated with TCAH movement into vineyards; models may need to include information other than temperature to accurately predict population development and movement behavior (Conclusions 4-32, 4-33).
Recommendation 4-24 (MP): Support research on the seasonal virus spread of GRBV by TCAH, focusing on year-long TCAH abundance and overwintering behavior throughout California.
RESEARCH AND ACTIONS THAT MAY YIELD THE MOST PROMISING MANAGEMENT SOLUTIONS
To sustain the wine grape industry, improvements in short-term stopgap measures are needed as research to develop longer-term solutions is pursued. Stopgap measures include the use of vines free of GLRaVs and GRBV to help prevent the introduction of GLRaVs and GRBV into vineyards, removal of infected plants (roguing), and vector management to reduce virus transmission and spread. The high-priority (HP) and medium-priority (MP) recommended actions and research (Box S-3) are meant to increase the efficacy of practices and tactics for GLD and GRBD management in the short and long term.
BOX S-3
Recommended Research and Actions for Improving GLD and GRBD Management
The recommended research and actions in the following sections would contribute to GLD and GRBD management in the short term.
Clean Plants
Recommendation 5-1 (HP): Encourage the adoption and implementation of higher sanitary standards in registered mother blocks using robust, state-of-the-art, sensitive, and reliable diagnostic methods and roguing of infected vines to maintain disease-free stock and provide clean planting materials for growers.
Roguing Infected Vines
Recommendation 5-2 (HP): Support research to develop optimal roguing and replanting schemes and techniques to manage GLD and GRBD and to facilitate their implementation by growers.
Vector Management
Recommendation 5-3 (HP): Support research to determine the optimal conditions for the application of systemic insecticides to achieve better mealybug control.
Recommendation 5-4 (HP): Develop and implement insecticide resistance management programs and support research to develop new active ingredients for mealybug management, including by evaluating the efficacy of natural products, such as plant essential oils, that could provide additional options for both organic and conventional vineyards.
Recommendation 5-5 (HP): Support research to determine the optimum conditions for the application of insecticides to achieve better TCAH control and to establish economic or action thresholds to guide insecticide application programs.
Recommendation 5-6 (HP): Support research to generate information needed for improving the efficacy of mating disruption for mealybug control and to determine the benefits (economic and otherwise) of employing this technique as part of an integrated approach to manage insect vectors in grapevines.
Recommendation 5-8 (MP): Support research to determine the costs and benefits of removing vegetation that harbors TCAH in and around vineyards and the use of trap crops to inform grower decision making regarding the employment of these methods for managing TCAH in vineyards.
Sanitation
Recommendation 5-10 (HP): Support research to determine the most effective and practical farm and worker equipment sanitation measures and harvesting and pruning strategies that can help minimize the spread of insect vectors.
Physical Barriers
Recommendation 5-11 (MP): Support research to evaluate the efficacy of physical barriers in deterring TCAH movement from natural or vineyard-adjacent habitats to vineyards.
Recommendation 5-12 (MP): Support research to evaluate the efficacy of reflective mulches in reducing the abundance of insect vectors in vineyards and research on improving the longevity and durability of reflective mulches.
Areawide Pest Management
Recommendation 5-13 (HP): Support efforts to develop areawide GLD and GRBD vector management programs for regions of California with different threat levels from these diseases, along with activities to encourage grower participation in these programs.
The recommended research and actions in the following section would contribute to GLD and GRBD management in the long term.
Host Plant Resistance
Recommendation 5-14 (HP): Support research using traditional and bioengineering approaches for developing GLD and GRBD resistance; when conducting resistance screening assays, the biological vector should be used as much as possible.
Recommendation 5-17 (HP): Establish multidisciplinary and trans-institutional collaborations to enhance synergies in pursuing bioengineering approaches, such as RNA interference (RNAi)-mediated resistance and clustered regularly interspaced short palindromic repeats (CRISPR)/Cas-based genome-editing technologies, as an alternative to traditional breeding for resistance against GLD and GRBD.
CONSIDERATIONS FOR FUTURE RESEARCH ON GRAPEVINE VIRUSES AND DISEASES
The committee also developed recommendations regarding future considerations for the CDFA PD/GWSS Board as it continues to support research to develop viable solutions to virus diseases that threaten vineyard health and the sustainability of the California wine grape industry. The high- and medium-priority recommendations are presented in Box S-4 and labeled HP and MP.
BOX S-4
Future Considerations
New Genetic Tools and Research Platforms
Genetic pest management strategies, in which the insect vector is modified rather than the plant, could aid disease control via vector population replacement and/or suppression. The biology of mealybugs makes them good targets for genetic pest management.
Recommendation 6-1: Support basic research to enable genetic pest management strategies for GLD and GRBD vectors and support modeling and sociological research to predict whether these strategies will be effective in the field and be accepted by consumers.
Approaches Used in Other Pathosystems
RNAi has the potential for use in managing insect vectors. RNAi biopesticides should have narrow activity based on target-specific double-stranded RNA (dsRNA) that will trigger RNAi suppression only in the targeted organism and no activity in other insects. Genetically engineered plants expressing dsRNA may more effectively manage mealybugs and other insects that reside under bark, where it is hard to contact them with insecticide sprays.
Recommendation 6-2 (MP): Consider supporting interdisciplinary research teams to advance RNAi research for the suppression of vectors in vineyards.
Trunk injection, which has been shown to be effective in controlling vasculature diseases and insect pests in other tree crops, could be applicable to the grapevine industry in California. Studies conducted in European vineyards have demonstrated the potential to control esca disease complex by injecting fungicides and chemicals into the grapevine trunk. This approach could help with vector or disease management in the medium or long term.
Recommendation 6-4 (MP): Consider supporting research to investigate the potential utility of trunk injection to control vectors with various pesticides (including new approaches such as RNAi and nanobodies) in grapevines.
Insect population models and disease risk models have been valuable tools for stakeholders to understand pest risk and production practices that mitigate risk, and to identify critical windows of time for scouting and management activities. These models could help with vector and disease management in the short term.
Recommendation 6-5 (HP): Fund research that will lead to the development of publicly available, regionally relevant insect population models and disease risk
models that can be used to guide local and areawide management activities for GLD and GRBD.
Engaging a Wider Range of Researchers
Researchers who are not familiar with the PD/GWSS Board research and outreach grants may not be aware that this program also funds research on other grapevine pests and diseases, such as GLD and GRBD. Allocating specific funding for early and mid-career scientists may help expand the pool of researchers working on grapevine virus diseases. Inviting researchers to address specific knowledge gaps may increase the pool of interested researchers.
Recommendation 6-6 (HP): To draw in diverse researchers, consider changing the name of the PD/GWSS Board research and outreach grants to accurately reflect the scope of its RFPs, which include multiple grapevine virus diseases and their insect vectors.
Recommendation 6-8 (MP): Consider offering specific funding for early- and mid-career researchers to encourage engagement in grapevine virus diseases research and build a network of scientists to address long-term questions.
Recommendation 6-9 (HP): Consider developing additional funding mechanisms to address particular needs for GLD or GRBD research, such as through inviting specific researchers to address particular knowledge gaps or accepting off-cycle proposals for projects that have potential to generate information for dramatically improving GLD and GRBD management.
Longer-Term and Replicated Studies
The study of complex systems such as vector-borne diseases in perennial crops may take longer than three years and more funding to accurately describe disease biology and inform recommendations for disease and vector management.
Recommendation 6-10 (HP): Consider funding longer-term projects (lasting more than three years), such as studies that advance control recommendations, translational research, and projects that integrate economic and societal impacts.
Another important issue is replicability of results. Collaborative research proposals provide a mechanism to support multiple research teams addressing the same research questions.
Recommendation 6-11 (HP): Consider funding research to replicate experimental results in more than one location and with different research teams to obtain more robust and reliable insights.
Recommendation 6-12: Consider new ways to leverage available funds using different proposal and award structures to encourage collaboration.
Knowledge Sharing and Collaborative Research
Greater sharing and integration of research findings could be facilitated by the establishment of a dedicated working group and/or through expanded opportunities for researchers to interact and share ideas at in-person meetings.
Recommendation 6-14 (MP): As an alternative to the annual Pierce’s disease symposium, consider coordinating with other organizations to hold sessions on GLD and GRBD at events such as the annual conference of the American Society for Enology and Viticulture and the Unified Wine and Grape Symposium. These sessions could also serve as a platform to facilitate new collaborations involving scientists working on other grape diseases or working in other wine grape producing regions.
Recommendation 6-16 (HP): Explore the feasibility of creating a working group, supported by the wine grape industry and funded by another entity, that can facilitate information sharing and foster collaboration among GLD and GRBD researchers.
Education and Outreach
A lack of communication and knowledge dissemination contributes to the non-adoption of GLD and GRBD management practices; this underscores the importance of having more effective educational and outreach strategies as the knowledge of GLD and GRBD advances.
Recommendation 6-18 (HP): Provide opportunities for funded researchers to share findings and recommendations regarding grapevine viruses via a dedicated website or a virtual town hall that facilitates interactive discussions about GLD and GRBD among researchers, extension agents, and growers.
Successful control of vector-borne diseases does not rely solely on understanding the pathosystem and devising strategies to control the pathogen or its vector; it also relies on what growers decide to do. Social science research has shown that social networks play an important role in learning and in the adoption of innovations.
Recommendation 6-19 (HP): Support research to better understand the sociological aspects of managing vector-borne diseases through collective action (i.e., areawide pest management) and find ways to increase grower participation in areawide pest management programs.
Recommendation 6-20 (HP): Support research on understanding and improving the flow of information across grower social networks and on outreach efforts to understand the drivers and barriers to successful adoption of GLD and GBRD management practices.
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