Duncan’s research ‘blew up preconceived ideas,’ improved almond, peach, grape production

Roger Duncan, shown talking with Ken Shackel, UC Davis pomologist, and Helen Dahlke, UC Davis hydrologist, in an almond orchard for a groundwater recharge project, collaborated with numerous UC ANR colleagues on research.

Roger Duncan, UCCE farm advisor in Stanislaus County, retires after 36 years

For more than three decades, tree fruit and nut growers have depended on the advice of Roger Duncan, UC Cooperative Extension pomology farm advisor in Stanislaus County, to improve their production practices. Duncan, whose research and extension program focused on almonds, peaches, grapes and other tree crops, retired July 1.

“Roger Duncan has been an extraordinarily relevant researcher for the predominant crops in Stanislaus County,” said Rep. John Duarte, owner of Duarte Nursery in Hughson. “His research has encompassed rootstock and variety selection, tree spacing, chemical inputs and spraying, fertilizers, pruning and replanting amongst other projects.”

Duncan began working for UC ANR in 1988 as a field assistant to Integrated Pest Management advisor Jim Stapleton after earning a master's degree in plant science and plant pathology from Fresno State and a bachelor's degree in the same subjects from UC Davis. In 1990, he became a UC Cooperative Extension in pomology farm advisor in Stanislaus County.

“I am most proud of the trust I have developed with the growers and other clientele,” said Roger Duncan, who retired as UC Cooperative Extension pomology farm advisor in Stanislaus County.

During Duncan's tenure, the planted acreage of tree and vine crops has tripled in Stanislaus County to nearly 1,900 farms on over 230,000 acres. His research has helped to improve production efficiency through improved rootstocks, crop varieties and production practices.

“Roger provides growers with resources and tools on nutrition, sprays, nutrient deficiencies, calendars, costs, pest management and other horticultural practices,” Duarte said. “His work has had significant impact on the productivity and quality of almonds, peaches and grapes. Breeders, universities, nurseries, growers and marketers have all gained from the wisdom and dedication of Roger Duncan.”

Growing up in Modesto, Duncan wasn't raised on a farm. “I had friends whose families farmed orchard crops, so I had some exposure,” he said. “I caught the Extension bug while working as a summer intern for the pomology advisors in the Stanislaus County UCCE office after I graduated with my B.S. That is what inspired me to return to school with the goal of being a pomology farm advisor.”

Duncan hosted several field events each year. For over 20 years, he coordinated the annual North San Joaquin Valley Almond Days, which attracted more than 500 attendees.

Reducing production costs

To help growers lower production costs, Duncan introduced orchard practices aimed at reducing hand labor and other inputs. As a result of his research, minimal pruning has become the norm in California almond production, reducing input costs and carbon output and increasing yield. He also improved monitoring and management techniques of established and invasive diseases and insect pests.

“The practical applications Roger brings to the grower community are invaluable,” said Mel Machado, Blue Diamond Almonds vice president for member relations and Stanislaus County almond grower. “His minimal pruning study stood growers on their heads. People had preconceived ideas about pruning. He blew that up. His research showed that after you get the tree's frame, all you need to remove are the dead and occluded branches. With the market depressed, we needed to cut costs. He said, ‘You don't need pruning.' Now I'm growing bushes.”

Art Bowman, a crop adviser with Salida Ag Chem, agreed that Duncan's pruning research had an impact. “Roger's pruning trial that lasted over 20 years was a much-discussed subject among growers,” Bowman said. “Growers' pruning practices definitely changed due to Roger's research, with early emphasis on structural development and, later in the tree's life, concentrating on tree accessibility and deadwood removal.”

In 1990, when Duncan joined UC Cooperative Extension, California had 408,700 acres of almonds, according to the California Agricultural Statistics Service. Now the state has over 1.5 million acres of almonds.

About 75% of the farms Duncan has served have 40 acres or less, farmed by “small” or “part-time” farmers, who needed to learn basic horticulture and pest management. Stanislaus County also is home to some very large, sophisticated growers, who Duncan has kept apprised of new technology.

“I believe that personal interaction offers the most memorable means of information transfer, which is why I held an average of 12-plus extension events per year, gave 18-plus extension presentations per year, and went on an average of over 75 individual farm calls per year,” Duncan said. He also provided information via videos, blogs, podcasts, radio shows, newsletters, news media and extension publications as well as commodity boards.

Along with Duncan's research, Bowman has appreciated his availability. “Roger was always ready to take a call, make orchard visits and listen to a grower's concern or problem,” he said. 

In 1997, Duncan began hosting twice monthly Tree & Vine Integrated Pest Management breakfast meetings for pest control advisers and growers to discuss current and potential pest threats. These meetings have continued for 28 years.

Duncan and the Tree & Vine Integrated Pest Management breakfast meeting team won the California Department of Pesticide Regulation’s IPM Innovator Award in 2016.

He speaks ‘farmer'

Machado attributes much of Duncan's success to his communication skills. “His research is scientific and he speaks ‘farmer,'” he said.

Machado gave rootstock as an example. “Roger is my rootstock resource; he knows rootstocks better than anybody,” he said. “His rootstock trial is dirt simple. There's a different rootstock every five trees. You can see walking down the row the differences in the rootstocks.”

From his field evaluations, Duncan identified a complex hybrid rootstock that is highly tolerant to ring nematode, bacterial canker and salt toxicity. He found other hybrid rootstocks that boost crop yield while reducing risk from soil chemistry and soil-borne disease challenges, enabling almonds to be grown in the marginal soils on the west side of the North San Joaquin Valley. To help growers choose the appropriate rootstock for their soil, he wrote a comprehensive ANR publication, made a video and worked with the UC Fruit & Nut Center to create an interactive rootstock comparison website.

Over the last 15 years, use of hybrid almond rootstocks has increased dramatically. Burchell Nursery now sells approximately 40% of their trees on hybrid rootstock compared to less than 5% of almond trees 15 years ago, and more than 95% of Duarte Nursery almond trees are on hybrid rootstocks, according to Duncan. 

“We've worked with Roger for years, back when he didn't have a mustache and then when he had a mustache,” said Robert Longstreth, who grows almonds, walnuts and cherries.

“Roger does research in the area you need, not frivolous stuff that you don't need,” said Longstreth, who has benefited from Duncan's research on pruning, rootstocks, irrigation timing, plant nutrition and disease control. “He's thought very highly of by almond growers. When he has something to say, people listen.”

The UCCE farm advisor has overseen long-term trials to learn how to design and maintain an almond orchard to capture early production, maintain long-term yields and maximize profits. “In the first 17 years of the orchard design project, I increased cumulative net profits by up to $14,000 per acre, including increased yield while reducing labor and carbon inputs,” Duncan said.

Influenced by Duncan's tree-spacing research results, growers have increased almond tree density by 20% per acre statewide, leading to higher crop yields, longer-living orchards and better farm economic sustainability.

As California's expert on almond rootstocks and almond orchard design, Duncan has taught the subjects for the UC Almond Production Short Course, was lead author on the UCANR publication “Almond Rootstocks,” wrote the rootstock chapter, and co-authored the orchard design chapter of the UC Almond Production Manual. He was invited to Chile, Spain and Australia to share his expertise with growers there.

“I felt very lucky to serve as an advisor in the same county where I was born and raised,” Duncan said.

Expanded programs for kids and gardeners

In addition to being a farm advisor, Duncan served as director of UC Cooperative Extension in Stanislaus County from 2011 through 2013 and again from 2017 through 2020. As the UCCE county director, he acquired new county funding to hire a 4-H youth development program representative in 2018 to provide more learning opportunities for local, underrepresented children.

That year, he also acquired county funding to hire a full-time Master Gardener coordinator and launched the first UC Master Gardener Program in the county.

“I felt very lucky to serve as an advisor in the same county where I was born and raised,” Duncan said. “I am most proud of the trust I have developed with the growers and other clientele.”

Professional awards

Recently, Duncan's peers at UC ANR honored him with a Distinguished Service Award for his outstanding extension program, which gave growers the data and confidence to adopt orchard practices that have bumped up the productivity and economic value of California almond orchards.

The popular breakfast meetings to discuss pest management earned Duncan and his UC Cooperative Extension farm advisor colleagues the Entomological Society Award of Extension Excellence and the California Department of Pesticide Regulation's IPM Innovator Award. The California Legislature also recognized the breakfast club's commitment to sustainable pest management.

Recognizing Duncan's extraordinary contributions, the university recently granted him emeritus status.

“I have a lot of respect for the other farm advisors, but Roger is at the top of the pile,” said Machado, who has served on Almond Board committees with Duncan and known him since he joined UC Cooperative Extension. “I'm going to miss him. You can absolutely count on him.”

Congressman and nurseryman Duarte added: “While he will be sorely missed by us in his role of pomology advisor for the University of California, we hope that he keeps his interest, and continues to influence the food production industry in the Central Valley.”

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