Outbreaks similar to El Niño-influenced issues of the 1990s

The wave of atmospheric rivers that swept across the state this winter has created the right conditions for plant pathogens that haven't been seen for decades in California. University of California, Davis, plant pathologist Florent “Flo” Trouillas is getting more calls from growers and farm advisors concerned about potential crop damage.

“Generally, whenever you have rain events, you're going to have problems,” said Trouillas, a Cooperative Extension specialist who is based at the Kearney Agricultural Research and Extension Center in Parlier. “In wet years we get really busy because most pathogens need and like water.”

Trouillas is like a disease detective. He splits his time between the field and the lab, working to diagnose pathogens, diseases and other ailments that strike fruit and nut crops such as almonds, cherries, olives and pistachios.

On a recent visit to an almond orchard near Fresno, Trouillas joined Mae Culumber, a nut crops farm advisor for UC Cooperative Extension Fresno County. A few weeks earlier, the two had walked the orchard, taking note of the base of some trees that had gumming — a thick, jelly-looking substance indicating a pathogen had taken hold.

“A lot of what Florent is doing is trying to assess patterns on a landscape,” Culumber said. “Sometimes things may look like they are one thing, but it could be another problem.”

When the two returned weeks later, the amber-colored gumming had moved into the canopy, looking like gumballs stuck to branches, some of which were already dead. “It's getting out of control from before,” Trouillas says. “This branch was killed. This is widespread.”

From the field to the lab

Lab testing confirmed what Trouillas believed was the culprit: Phytophthora syringae, a pathogen that can affect almond crops but is rarely seen in California. If it is found, generally the site of infection are wounds caused by pruning, but that is not the case here, where the infection began in the canopy at twigs, or small branches.

It is a threat to a key crop, which according to the California Department of Food and Agriculture, generates $5 billion annually. The last time Phytophthora syringae hit California was in the 1990s after a series of El Niño-influenced storms. Trouillas, who has a photographic memory, remembered reading about it in an old manual.

“It's rare for California and one that we see mostly following atmospheric rivers,” he says.

“The disease will only happen following these extremely wet winters.”

Phytophthora is soilborne, mostly found in tree roots, and doesn't generally spread up into branches. But the intense storms created the right conditions for the pathogen to “swim” up trunks as winds blew spores into the air and rain dropped them back down into the canopy, Trouillas said.

Some of the trees in this orchard will die; others can be saved by pruning infected branches and applying a recommended fungicide, he said.

Identification, diagnosis, education

Trouillas is one of more than 50 Cooperative Extension specialists at UC Davis and each is charged with identifying problems and developing solutions for those issues in support of agriculture, the ecosystem and communities throughout the state.

In his role, Trouillas focuses not only on pathology and research but also on educating growers, nursery staff, pest control advisers and others in agriculture about ways to manage potential threats and how to prevent crop damage.

“His role is very crucial,” said Mohammad Yaghmour, an orchard systems advisor for UC Cooperative Extension Kern County. “He's not only on this mission to educate growers but he's also a source of education for us.”

Trouillas typically conducts one or two site visits a week, usually after a farm advisor reaches out about a problem they can't solve on their own.

“This allows us to be at the forefront of disease detections in California,” he said.

He likens these visits to house calls a doctor would make, only to fields instead. And one of those calls recently took him to a cherry orchard in Lodi.

“These guys help me quite a bit,” said Andrew Vignolo, a pest control adviser with Wilbur-Ellis who asked for a consult. “I bug them a lot.”

The visit starts like any consult in a doctor's office, only the questions come fast as they walk around the Lodi orchard where branches are dying, there is gumming and the trees appear stressed. Some look to be sunburned from exposure. Old pruning wounds show cankers, indicating that past disease treatments didn't get rid of whatever was affecting the trees.

Trouillas asks about the cultivar of the trees because some varieties are more susceptible to pests or diseases. He focuses on stress because that opens the door to disease.

Do they prune in the dormant winter months or in summer when pathogens are more prevalent? Does the soil get tested? How old are the trees? What about nutrition?

“I'm trying to figure out how they got infected so bad,” Trouillas said, walking the orchard. “Bacterial canker is a very mysterious disease.”

He thinks it might be a bacterial canker disease and shaves some bark to take to the lab for testing. He wants to come back next winter to take some samples to see where the pathogen is overwintering.

“We'll know in a few weeks if we have a fighting chance,” Vignolo said.

Be it Lodi, Fresno or elsewhere in the state, Trouillas focuses on local conditions. But what is learned in one field can be passed on to others, providing early warnings or advice for those in similar situations. “All these efforts at collaboration, from the field, to the lab, going through research projects, there's only one goal here — to help the farmers of California.”

Two UC Cooperative Extension scientists have been selected as Presidential Chairs for Tree Nuts at University of California Agriculture and Natural Resources.

Giulia Marino, UCCE specialist, will be the Presidential Chair for Tree Nut Genetics and Mae Culumber, UCCE nut crops advisor, will be the Presidential Chair for Tree Nut Soil Science and Plant Water Relations, announced Glenda Humiston, UC vice president for agriculture and natural resources.

The endowed chairs will give the two scientists a dedicated source of funding for five years for their ongoing agricultural research. UC Agriculture and Natural Resources established the two $1 million endowments in 2015. Half of the funds for the endowed chairs was donated by the California Pistachio Research Board and the other half was provided by UC Office of the President.

“The California Pistachio Research Board appreciated the opportunity to create these Presidential Chairs with the dedicated flexible funding it provides the scientists,” said Bob Klein, manager of the California Pistachio Research Board. “Mae and Giulia have stellar research records, have a history of research on California pistachios, and deserved both consideration and the award of these Chairs. The Board was pleased with the previous incumbents and is now looking forward to working with both Giulia and Mae in their programs on Genetics and Soil Science/Water Relations.”

Marino, who joined UC ANR in 2020, is based at UC Kearney Agricultural Research & Extension Center in Parlier. Her research integrates germplasm preservation and evaluation with tree physiology to improve orchard system profitability and abiotic-stress resilience. She explores the interactions between cultivar-rootstock traits, soil conditions and management practices.

“The funding from the presidential chair of tree nuts genetics will allow me to evaluate the horticultural and physiological performance of some promising new scion-rootstock options stemming from the UC pistachio breeding program developed by Craig Kallsen, UCCE farm advisor for Kern County, and Dan Parfitt, UC Davis professor emeritus,” Marino said. 

“The program has the objectives of increasing the genetic diversity of the scion and rootstock cultivars used by the pistachio industry to improve grower returns and reduce its susceptibility to climate change,” Marino continued. “Rootstock projects include novel rootstocks more tolerant of boron in irrigation water, dwarfing rootstocks for higher early yields and more efficient use of pruning and harvest inputs. Scion objectives include novel scions for higher yield and trees less sensitive to inadequate winter chilling.”

One of her current research lines focuses on the characterization of low vigor cultivars and/or rootstocks to increase orchard planting density and reduce management costs in olive, pistachio and almond. She develops protocols for irrigation management based on genotype-specific physiological responses to water stress. Marino also studies the impact of saline sodic soil conditions on pistachio physiology and of low winter chill on cherry and pistachio tree and fruit physiology.

Marino earned a doctoral degree in fruit and forestry tree systems and master's and bachelor's degrees in agricultural science, all from the University of Palermo in Italy.

Culumber, UCCE nut crops advisor for Fresno and Kings counties, focuses on enhancing the sustainability and viability of nut crop production through applied research and outreach education with emphasis on soil and water conservation and reducing the impact of production practices on air quality and greenhouse gas emissions. Culumber partners with fellow UC advisors, specialists, campus faculty, growers and other industry stakeholders to find practical, sustainable solutions for issues including soil salinity, tree training and pruning, tree nutrition, and pest and disease management. 

“As Presidential Chair, I will utilize these generous funds from the Pistachio Research Board to augment my collaborative outreach extension and applied research efforts to understand 

and develop solutions to soil and water quality problems faced by pistachio growers and other nut crop producers across the San Joaquin Valley,” Culumber said.

She is collaborating on a CDFA Fertilizer Research and Education Program project that provides irrigation and nitrogen management training for certified crop advisors and growers to adopt practices that conserve water and protect water quality. She is also studying how to improve estimates of crop evapotranspiration and forecasting for major California crops for more precise irrigation. Culumber is leading research on the effects of whole orchard recycling on air quality and climate resilience, soil health, tree growth and productivity in second-generation orchards. 

Culumber earned a Ph.D. in soil science and agroecology and a master's in plant science and molecular ecology, both from Utah State University, and a bachelor's in biology from University of Wisconsin-Stevens Point.

Bruce D. Lampinen, UC Cooperative Extension integrated orchard management, walnut and almond specialist in the UC Davis Department of Plant Sciences, received the first Presidential Chair for Tree Nut Soil Science and Plant Water Relations. Craig Kallsen, UC Cooperative Extension farm advisor in Kern County who specializes in fruit and nut crops, received the Presidential Chair for Tree Nut Genetics.

A delegation of 12 UC ANR staff, academics, volunteers and stakeholders visited state legislators in Sacramento on April 19 for UC ANR Advocacy Day to share how UC ANR's work delivers local, place-based education, outreach and programming to serve communities throughout the state.

Anne Megaro, government and community relations director, and Christina Harrington, student assistant, UC Master Gardener and graduate of the UC California Naturalist Program, organized meetings with Assembly Member Rebecca Bauer-Kahan, Senator John Laird, Assembly Member Devon Mathis, and staff members in many legislative offices.

The delegation thanked them for investing in ongoing funding in last year's state budget and shared their stories of serving community members, farmers, ranchers, youth and natural resource managers in their regions.

Vice President Glenda Humiston and Mark Bell, Vice Provost of Strategic Initiatives and Statewide Programs, led two teams, which included Sarah-Mae Nelson, UC Climate Stewards initiative academic coordinator; Kamal Khaira, director of CalFresh Healthy Living, UC; UCCE advisors Igor Lacan, Mae Culumber and Dorina Espinoza; 4-H Youth State Ambassadors Megna Nayar and Sara Tibbets; and Clio Tarazi, UC Master Gardener volunteer.

The teams urged legislators to support several key budget requests as part of Governor Newsom's proposed FY 2022-23 state budget. These budget commitments would support UC's much-needed capital projects at Research and Extension Centers and Elkus Ranch to expand capacity for research and programming, as well as investments for UC climate action and resiliency projects that will advance climate research and workforce development programs for students and community members. 

The UC ANR representatives invited the legislators to visit for tours and events to see UC ANR at work in their districts firsthand.

 

Two UC Cooperative Extension scientists have been selected as Presidential Chairs for Tree Nuts at University of California Agriculture and Natural Resources.

Giulia Marino, UCCE specialist, will be the Presidential Chair for Tree Nut Genetics and Mae Culumber, UCCE nut crops advisor, will be the Presidential Chair for Tree Nut Soil Science and Plant Water Relations, announced Glenda Humiston, UC vice president for agriculture and natural resources. 

The endowed chairs will give the two scientists a dedicated source of funding for five years for their ongoing agricultural research. UC Agriculture and Natural Resources established the two $1 million endowments in 2015. Half of the funds for the endowed chairs was donated by the California Pistachio Research Board and the other half was provided by UC Office of the President.

“The California Pistachio Research Board appreciated the opportunity to create these Presidential Chairs with the dedicated flexible funding it provides the scientists,” said Bob Klein, manager of the California Pistachio Research Board. “Mae and Giulia have stellar research records, have a history of research on California pistachios, and deserved both consideration and the award of these Chairs. The Board was pleased with the previous incumbents and is now looking forward to working with both Giulia and Mae in their programs on Genetics and Soil Science/Water Relations.”

Marino, who joined UC ANR in 2020, is based at UC Kearney Agricultural Research & Extension Center in Parlier. Her research integrates germplasm preservation and evaluation with tree physiology to improve orchard system profitability and abiotic-stress resilience. She explores the interactions between cultivar-rootstock traits, soil conditions and management practices.

“The funding from the presidential chair of tree nuts genetics will allow me to evaluate the horticultural and physiological performance of some promising new scion-rootstock options stemming from the UC pistachio breeding program developed by Craig Kallsen, UCCE farm advisor for Kern County, and Dan Parfitt, UC Davis professor emeritus,” Marino said.  

“The program has the objectives of increasing the genetic diversity of the scion and rootstock cultivars used by the pistachio industry to improve grower returns and reduce its susceptibility to climate change,” Marino continued. “Rootstock projects include novel rootstocks more tolerant of boron in irrigation water, dwarfing rootstocks for higher early yields and more efficient use of pruning and harvest inputs. Scion objectives include novel scions for higher yield and trees less sensitive to inadequate winter chilling.” 

One of her current research lines focuses on the characterization of low vigor cultivars and/or rootstocks to increase orchard planting density and reduce management costs in olive, pistachio and almond. She develops protocols for irrigation management based on genotype-specific physiological responses to water stress. Marino also studies the impact of saline sodic soil conditions on pistachio physiology and of low winter chill on cherry and pistachio tree and fruit physiology.

Marino earned a doctoral degree in fruit and forestry tree systems and master's and bachelor's degrees in agricultural science, all from the University of Palermo in Italy.

Culumber, UCCE nut crops advisor for Fresno and Kings counties, focuses on enhancing the sustainability and viability of nut crop production through applied research and outreach education with emphasis on soil and water conservation and reducing the impact of production practices on air quality and greenhouse gas emissions. Culumber partners with fellow UC advisors, specialists, campus faculty, growers and other industry stakeholders to find practical, sustainable solutions for issues including soil salinity, tree training and pruning, tree nutrition, and pest and disease management. 

“As Presidential Chair, I will utilize these generous funds from the Pistachio Research Board to augment my collaborative outreach extension and applied research efforts to understand 

and develop solutions to soil and water quality problems faced by pistachio growers and other nut crop producers across the San Joaquin Valley,” Culumber said.

She is collaborating on a CDFA Fertilizer Research and Education Program project that provides irrigation and nitrogen management training for certified crop advisors and growers to adopt practices that conserve water and protect water quality. She is also studying how to improve estimates of crop evapotranspiration and forecasting for major California crops for more precise irrigation. Culumber is leading research on the effects of whole orchard recycling on air quality and climate resilience, soil health, tree growth and productivity in second-generation orchards. 

Culumber earned a Ph.D. in soil science and agroecology and a master's in plant science and molecular ecology, both from Utah State University, and a bachelor's in biology from University of Wisconsin-Stevens Point.

Bruce D. Lampinen, UC Cooperative Extension integrated orchard management, walnut and almond specialist in the UC Davis Department of Plant Sciences, received the first Presidential Chair for Tree Nut Soil Science and Plant Water Relations. Craig Kallsen, UC Cooperative Extension farm advisor in Kern County who specializes in fruit and nut crops, received the Presidential Chair for Tree Nut Genetics.