Production Research Papers - California Walnuts

Production Research Annual Progress Reports

Each year, the CWB’s production research program solicits project proposals from our University of California, US Department of Agriculture – Agriculture Research Service, California State University and other institutional research partners to address our industry’s orchard production challenges. Administered by the CWB’s Production Research Committee, the program includes a very deliberate, thorough, and dynamic processes for keeping abreast of challenges the industry faces and ensuring that the research efforts funded by crop assessments are focused on delivering both applied and long-term benefits to growers and handlers.
Most research projects run for multiple years because it often takes several years of repetition and refining to ensure results are repeatable across varied regions and orchard situations. All CWB-funded project leaders submit annual written project reports, due each year in December. These reports form the basis for an evaluation of whether projects are progressing toward completion of stated objectives and, if requested, their worthiness for continued funding the following year.

To make the year-to-year findings of industry-funded research projects more accessible‒and to ensure that results of past research are safely and securely “archived” for future reference‒the CWB has partnered with UC Davis to store written reports in an accessible and searchable database managed by the UC Davis Fruit & Nut Research & Information Center. The database can be found at https://ucanr.edu/sites/cawalnut/. Walnut growers and handlers interested in following the details of CWB-funded research projects are encouraged to access the database, which is updated each year in March with reports from the previous year’s projects.

Production research efforts fall into four categories: Variety & Rootstock Breeding, Plant Pathology and Nematology, Entomology (Insect and mite pests), and Orchard Management. The latter category is broad and includes orchard irrigation, nutrition, tree canopy architecture & management, weed control & orchard floor management, as well as tree and physiology, growth & development.
The research reports housed in the UC Davis database are detailed and technical accounts of what was accomplished in the most recent year of the project. And, because they represent just a single year of what is normally a multi-year effort, it can be difficult to sift out practical “take-home” findings ready for orchard use.
Beginning in 2020, the CWB began requiring that project leaders prepare short 1- to 2-page project progress reports that capture the background, methods, and key findings of their projects in a concise, easy-to-read format. These reports, organized by the four production research areas of Orchard Management, Plant Pathology and Nematology, Entomology, and Variety and Rootstock Breeding , are available for viewing and downloading below. Future years’ updates will be added each spring.

Orchard Management

Effectiveness and Mechanisms of Dormancy Breaking Treatments for Walnuts

Project Leader: Katherine Jarvis-Shean
UC Cooperative Extension, Yolo, Solano, and Sacramento Counties
2024 Project Status: Year 3 of 3, Co-funded by Calif. Dept. of Food & Agriculture

Walnut Orchard Management: Pilot Projects, Field Testing, Adaptive Research and Problem Solving by C.E. Farm Advisors and Specialists

Project Leader: Bruce Lampinen
UC Cooperative Extension Specialist, Department of Plant Sciences, UC Davis
2024 Project Status: Ongoing with annual review

Weed Management in the Conventional Walnut Production System: Field Research and Extension

Project Leader: Brad Hanson
Department of Plant Sciences, UC Davis
2024 Project Status: Ongoing with annual review

Developing Nutrient Requirements for Young Walnut Orchards After Whole Orchard Recycling

Project Leader: Clarissa Reyes
UC Cooperative Extension, Sutter-Yuba, Butte & Counties
2024 Project Status: Year 1 of 3

Pilot On-Farm Irrigation Trial Using Automated Stem Water Potential Sensing

Project Leader: Ken Shackel
Department of Plant Sciences, UC Davis
2024 Project Status: Year 1 of 1

Integration of Row Spacing, Tree Spacing, and Rootstocks for Walnut Production

Cooperative Extension, Stanislaus County
Project Leader: Kari Arnold, UC
2020 Project Status: Year 5 of 5

High-Throughput Phenotyping of Walnut Yield

Project Leaders: Brian Bailey, Department of Plant Sciences, UC Davis
2020 Project Status: Year 1 of 2

Impacts Of Heading Height At Planting On Growth Dynamics Of ‘Ivanhoe’ Walnuts

Project Leader: Elizabeth J. Fichtner, UC Cooperative Extension, Division of Agriculture & Natural
Resources, Tulare County, Visalia, CA 93274
2020 Project Status: Year 1 of 1

Herbicide Performance and Safety Evaluations in the Conventional Walnut Production System: Field Research and Extension Support

Project Leader: Brad Hanson, Department of Plant Sciences, UC Davis
Ongoing with annual review

Effectiveness And Mechanisms Of Dormancy Breaking Treatments For Walnuts

Project Leader: Katherine Jarvis-Shean, UC Cooperative Extension, Division of Agriculture & Natural Resources (UCANR)
2020 Project Status: Year 2 of 4

Integrating Soil Moisture, Plant Monitoring, And Imagery For Site-specific Zone Irrigation Management In Walnuts

Project Leader: Isaya Kisekka, Department of Land, Air & Water Resources, UC Davis
2020 Project Status: Year 2 of 3

Walnut Orchard Management: Pilot Projects, Field Testing, Adaptive Research, And Problem Solving By Uc Farm Advisors And Specialists

Project Leader: Bruce Lampinen, Department of Plant Sciences, UC Davis
Ongoing with annual review

Early Season Water Management And Yield Limiting Factors In Walnut

Project Leader: Ken Shackel, Department of Plant Sciences, UC Davis
2020 Project Status: Year 2 of 5

Development of Tree Carbohydrate Budget-Based Methods for Sustainable Management of Walnut Orchards Under Changing Central Valley Climatic Conditions

Project Leader: Maciej Zwieniecki, Department of Plant Sciences, UC Davis
2020 Project Status: Year 2 of 4

Plant Pathology and Nematology

Epidemiology and Management of Walnut Blight

Project Leader: Jim Adaskaveg
Department of Microbiology and Plant Pathology, UC Riverside
2024 Project Status: Year 1 of 3

Determining Levels of Bot and Phomopsis in the Orchard; Effects of a Bloom Spray on Bot, Phomopsis, and Mold; and Effect of a Combination of Ethephon with a Fungicide Against Mold

Project Leader: Themis J. Michailides
Department of Plant Pathology, UC Davis
2024 Project Status: Year 2 of 2

Nematode-Resistant Walnut Rootstocks: Biotechnological Solutions for a Sustainable California Walnut Industry

Project Leader: Shahid Siddique
Department of Entomology and Nematology, UC Davis
2024 Project Status: Year 1 of 1

Implementing Soil Treatment Strategies for Suppression of Plant Parasitic Nematodes in Walnut

Project Leader: Andreas Westphal
Department of Nematology, UC Riverside
2024 Project Status: Year 2 of 3

Epidemiology and Management of Walnut Blight

Project Leader: J. E. Adaskaveg, Departments of Microbiology and Plant Pathology, UC Riverside
2020 Project Status: Year 2 of 3

METAGENOMIC-BASED FIELD MANAGEMENT OF WALNUT BACTERIAL BLIGHT DISEASE

Project Leader: Abhaya M. Dandekar, Department of Plant Sciences, UC Davis
2020 Project Status: Year 1 of 3

Etiology, Epidemiology, And Management Of Hull Rot And Mold Of Walnut In California

Project Leader: Themis J. Michailides, Department of Plant Pathology, UC Davis / Kearney Agricultural Research and Extension Center
2020 Project Status: Year 2 of 3

Investigating Botryosphaeria/Phomopsis Diseases Of Walnut In San Joaquin And Stanislaus Counties, California

Project Leader: Mohamed Nouri, UC Cooperative Extension, Division of Agriculture & Natural
Resources, San Joaquin County, Stockton, CA 95206
2020 Project Status: Year 1 of 1

Pre- And Post-plant Remedies For Nematode Infestations Of Walnut Orchards

Project Leader: Andreas Westphal, Department of Nematology, UC Riverside, Kearney Agricultural
Research and Extension Center, Parlier, CA
2020 Project Status: Year 3 of 5

Entomology

Biology and Management of Walnut Husk Fly (Rhagoletis completa) in Walnuts

Project Leader: Jhalendra Rijal
UC Cooperative Extension, Northern San Joaquin Valley
2024 Project Status: Year 3 of 3

Attract-and-Kill Strategy for Control of Walnut Husk Fly

Project Leader: Robert Van Steenwyk
Department of Environmental Science, Policy, and Management, UC Berkeley
2024 Project Status: Year 1 of 2

Grower/PCA Evaluation of the New Walnut Husk Fly Pheromone

Project Leader: Robert Van Steenwyk
Department of Environmental Science, Policy, and Management, UC Berkeley
2024 Project Status: Year 1 of 1

Improving Treatment Decisions for Navel Orangeworm in Walnuts

Project Leader: Houston Wilson
Dept of Entomology, UC Riverside
2024 Project Status: Year 3 of 3

FACTORS INFLUENCING PERFORMANCE OF WALNUT HUSK FLY TRAPPING SYSTEMS

Project Leader: Elizabeth “Betsy” Boyd, California State University, Chico
2020 Project Status: Year 1 of 2

MOVEMENT AND MONITORING OF NAVEL ORANGEWORM (AMYELOIS TRANSITELLA ) IN WALNUTS

Project Leader: Chuck Burks, USDA-ARS, Parlier, CA
2020 Project Status: Year 2 of 3

Monitoring for Walnut Husk Fly and Conducting a Needs Assessment of Walnut Growers in Lake County

Project Leader: Cindy Kron, North Coast IPM Advisor, UCANR
2020 Project Status: Year 1 of 1

Survey of Navel Orangeworm Strategies

Project Leader: Phoebe Gordon, UC Cooperative Extension, Madera and Merced Counties and Houston Wilson, UC Riverside
2020 Project Status: Year 1 of 1

Seasonal Pest Monitoring And Ipm Updates Of The North San Joaquin Valley

Project Leader: Jhalendra Rijal, UC Cooperative Extension, Northern San Joaquin Valley, Modesto, CA 95358
2020 Project Status: Year 1 of 1

Variety and Rootstock Breeding

Walnut Improvement Program

Project Leader: Pat J. Brown
Department of Plant Sciences, UC Davis
2024 Project Status: Ongoing with annual review

Putting Phenotypic and Genotypic Tools to Work for Improving Walnut Rootstocks

Project Leader: Pat J. Brown
Department of Plant Sciences, UC Davis
2024 Project Status: Year 2 of 3

Development of a Walnut Blight Protecting Rootstock

Project Leader: Abhaya M. Dandekar
Department of Plant Sciences, UC Davis
2024 Project Status: Year 2 of 3

Translating Genome Editing Tools for Walnut Improvement

Project Leader: Abhaya M. Dandekar
Department of Plant Sciences, UC Davis
2024 Project Status: Year 5 of 5

Defining the Susceptibility to Kernel Color Darkening

Project Leader: Abhaya M. Dandekar
Department of Plant Sciences, UC Davis
2024 Project Status: Year 1 of 3

Walnut Improvement Program

Pat J. Brown, Department of Plant Sciences, UC Davis
Ongoing with annual review

Genome Editing Tools for Walnut Improvement

Project Leaders: Abhaya M. Dandekar, Department of Plant Sciences, UC Davis
2020 Project Status: Year 1 of 5

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