Merced County Cooperative Extension
Merced County Cooperative Extension
Merced County Cooperative Extension
University of California
Merced County Cooperative Extension

UC Food Blog

New UCCE advisors bring fresh ideas to protect lettuce from INSV, Pythium wilt

UC Cooperative Extension advisors Kirsten Pearsons (left) and Yu-Chen Wang search ice plants for Western flower thrips, the insect that carries the impatiens necrotic spot virus (INSV). The disease has greatly impacted lettuce growers in the Salinas Valley. Photo by Daniel Hasegawa

Salinas Valley lettuce growers lost about $150 million in 2022 due to diseases

A stormy winter could portend another devastating year for the lettuce industry in the Salinas Valley, which saw approximately $150 million in lost gross revenue in 2022 due to INSV (impatiens necrotic spot virus) and associated diseases. Recent drenching rains might mean more weeds – overwintering “reservoirs” for the tiny insect, the Western flower thrips, that carries INSV.

Or the extreme precipitation could benefit growers, as thrips in the soil – during their intermediate stage of development – might be drowned in the waterlogged fields.

As with so many aspects of the INSV crisis, the ultimate effects of flooded fields on thrips populations remain unknown.

Yu-Chen Wang and Kirsten Pearsons

“We don't know if thrips are just so persistent and so stable in that pupal stage that maybe they will emerge unaffected,” said Kirsten Pearsons, University of California Cooperative Extension integrated pest management farm advisor for Santa Cruz, Monterey and San Benito counties. “There's just so much about their biology and ecology in the Salinas Valley that we just don't know.”

The mystery of thrips, INSV and soilborne diseases (namely Pythium wilt) is why UC Agriculture and Natural Resources assigned Pearsons to the area last November and hired Yu-Chen Wang in October as UCCE plant pathology advisor for the three counties.

“They're stepping in at a critical moment,” said Richard Smith, the region's UCCE vegetable crop production and weed science advisor who retired in January after a 37-year career. “They've gotten grants funded already – and that's just incredible. They're hitting the ground running.”

Experienced in disease diagnosis and collaboration with growers and industry partners, Wang said her pathology background – paired with Pearsons' entomology expertise – will be crucial in addressing INSV and other diseases.

“It is important for Kirsten and me to work together and provide different insights for the vector and the pathogen, respectively,” Wang said.

‘It's going to take everything to get a crop'

One priority is untangling the dynamics of INSV and Pythium wilt co-occurrence – the subject of ongoing research by JP Dundore-Arias, a plant pathologist at California State University, Monterey Bay. While the vegetables may tolerate one disease or the other, their one-two punch often deals the lethal blow. 

Lettuce showing signs of INSV infection and damage. Photo by Richard Smith

“The challenge is – which is why it's great to have Yu-Chen and Kirsten – is that we have so many problems now, whether it's Fusarium (wilt), or Verticillium (wilt), or Pythium, or INSV,” said Mark Mason, pest control adviser for Nature's Reward, which primarily grows lettuces on 5,000 acres across the Salinas Valley.

Mason said that co-infections on his crops (sometimes with three or four diagnosed diseases) make it difficult to assign monetary damages to a specific pathogen, but he noted he has seen fields with “100% loss.” According to the Grower-Shipper Association of Central California, about 11,500 acres were deemed not harvestable in 2022, representing 12% of lettuce industry acreage.

Given the gravity and complexity of the disease dilemma, Pearsons said she has been fielding calls from growers seeking new and better solutions – ways to improve existing tools, techniques borrowed from other crop systems, and additional biological or chemical means of control.

And although there are a couple of pesticides that manage the disease-carrying thrips reasonably well, growers and researchers are worried about their diminishing efficacy due to overuse. Plus, they only constitute a short-term fix.

“Managing the thrips will only reduce the amount of INSV that can get transmitted,” Pearsons explained. “You can kill 99.9% of the thrips, but you get one thrips that has INSV that enters a field, and now you have an infected lettuce plant. All of the thrips are going to come and they can spread it from there; pesticide slows things down, but it's not going to eliminate it.”

Wang, a plant pathologist, brings expertise in disease diagnosis to Monterey, Santa Cruz and San Benito counties. Photo courtesy of Cal Poly Strawberry Center

Finding disease-tolerant lettuce cultivars is a more sustainable approach. Trials conducted last year by Smith, Wang and others identified several varieties that appeared to hold up well to Pythium and INSV. While additional research could maximize their potential benefit, Wang said even the hardier cultivars will lose their resistance over time, and a multi-layered INSV strategy with “integrated management tools” is crucial.

“We realized, when this thing started happening, that we cannot spray our way out of this problem,” Mason said. “We need varieties; we need management practices; we need pesticides…it just seems like it's going to take everything to get a crop.”

Weeds key to disease control

An all-hands-on-deck approach helped control thrips-harboring weeds last winter. With fields drying out from January storms, Smith said communities must get back to weed management – with a focus on prominent weed hosts for INSV and neglected areas adjacent to farms. Hotspots of infection last year were traced to industrial lots that were overlooked during the weeding process.

“People can't lose sight of the fact that we still need to be controlling the weeds in key areas, because that's the reservoir of the virus during the winter,” Smith said. “We have to stay on task with that.”

Yet despite the diligent weed abatement, crop damage from INSV and Pythium was widespread in 2022, and Smith said it's “very possible” that high heat during the summer was a contributing factor to especially prevalent disease in fall. Thrips populations tend to thrive in warmer weather, Smith said, but much more research needs to be done to understand the basic biology of the insect, including how they acquire the virus and how they spread it.

High hopes for future

Pearsons cited the work of Daniel Hasegawa, a research entomologist with the U.S. Department of Agriculture, who leads teams in monitoring thrips populations in several locations across the Salinas Valley. Currently the counting of thrips on sticky card traps is done manually, but Pearsons and Mason mentioned the possibility of using AI and machine learning to expedite that process.

Pearsons, seen here talking with a small-scale farmer in San Luis Obispo County, says she looks forward to collaborating with Salinas Valley growers. Photo by Maria Orozco

Mason said that the grower community is excited about the new technologies and ideas that Pearsons and Wang are bringing to the region. As a participant in the search for candidates to fill the advisor positions, Mason said “they were, in my opinion, by far the best fit for what we were looking for.”

“I hope they stay here for 30 years,” he added.

The new advisors both noted the palpable energy and cooperative spirit in the Salinas Valley to proactively meet the challenge.

“Looking to the past, there have been other outbreaks and diseases that they've managed to overcome,” Pearsons said. “These farmers are resilient and creative and I fully believe that lettuce will still be growing here for years to come – it might look a little different, and it might take a little bit of a painful period to get to that point, but I think that we're going to be able to come up with some solutions.”

And while there are concerns that some lettuce growers might decide to leave the region, Wang said she also believes in the industry's strong roots and rich history.

“Salinas Valley has had a beautiful climate for lettuce for so many years; there are some undeniable advantages here,” she said. “This is still the best place in the United States – and maybe the world – to grow lettuce.” 

Posted on Friday, February 3, 2023 at 9:51 AM
Focus Area Tags: Agriculture, Food, Pest Management

Growers invited to see benefits of cover crops in orchards, vineyards

 

Sheep graze on cover crop at Burrough Family Farms. Photo by Benina Montes

Searchable database of growers experienced in growing cover crops launched

Growers are invited to tour orchards and vineyards and hear from other growers about their experiences with cover crops. 

UC Sustainable Agriculture Research and Education Program, UC Cooperative Extension, the Napa Resource Conservation District, and the Community Alliance with Family Farmers have created a searchable database of orchard and vineyard growers experienced in growing cover crops that will help other growers bring the benefits of the practice to their operations. 

“The tours are part of a project for which we recently unveiled new tools for orchard and vineyard growers to learn about cover cropping from experienced growers,” said Sonja Brodt, associate director of the UC Sustainable Agriculture Research and Education Program. 

The database describes cover cropping strategies, details of field practices, benefits and challenges experienced by cover crop growers in orchards and vineyards in the southern Sacramento Valley (including the Capay Valley) and the North Coast viticulture region. The cover crop grower database is available at https://sarep.ucdavis.edu/covercropsdb.

A mix of yellow mustard, black mustard and canola are grown between rows in an orchard. Photo by SAREP

Feb. 8, 1-5 p.m., Capay Valley tour: 

The tour will visit three organic farms in the Capay Valley that are integrating cover crops and grazing in their orchard and vineyard systems. Topics of discussion will include:

  • Strategies for integrating cover crops into orchards and vineyards
  • Impacts of cover cropping and grazing on soil health
  • Funding and information resources for growing cover crops

Speakers will include:

  • Rory Crowley, Director of Habitat Programs, Project Apis m.
  • Amélie Gaudin, Associate Professor, Department of Plant Sciences, UC Davis, Endowed Chair in Agroecology
  • Hope Zabronsky, Climate-Smart Agriculture Program lead, UC Agriculture and Natural Resources

To register for the Feb. 8 tour, visit https://sarep.ucdavis.edu/events/grazing-cover-crops-orchards-and-vineyards-capay-valley-tour.

March 8, 1-4 p.m., Arbuckle area tour: 

The tour will visit two conventional farms in the Arbuckle area that are integrating cover crops into their orchard and vineyard systems. 

Topics of discussion will include:

  • Strategies for integrating cover crops into orchards and vineyards
  • Impacts of cover cropping on soil and water balance
  • Frost risk protection and prevention
  • Funding resources for growing cover crops

Speakers will include:

  • Rory Crowley, Director of Habitat Programs, Project Apis m.
  • Kosana Suvocarev, UC Cooperative Extension Specialist in Biometeorology, UC Davis Department of Land, Air, and Water Resources
  • Hope Zabronsky, Climate-Smart Agriculture Program lead, UC Agriculture and Natural Resources

To register for the March 8 tour, visit https://sarep.ucdavis.edu/events/cover-cropping-conventional-orchards-and-vineyards-arbuckle-area-tour

Posted on Friday, January 13, 2023 at 1:13 PM
Focus Area Tags: Agriculture

NIFA funds $3.8 million project to find climate-resilient pistachio trees

With nearly 520,000 acres planted in California in 2021, pistachios are the fastest-growing tree nut crop in the state. California dominates the pistachio industry, growing 99 percent of the nation's crop and nearly 60 percent of the world's crop. Photo by Evett Kilmartin

Growers invited to participate in study by sharing their experiences

A multi-state team led by Patrick J. Brown has been awarded nearly $3.8 million over the next four years for a project to improve pistachio production as the industry faces warmer winters and scarcer water.

“We are at this unique point in history where we can do this,” said Brown, an associate professor in the UC Davis Department of Plant Sciences.

The project aims to ensure the industry can thrive in coming decades despite the challenges faced. Growers are invited to participate in the study, sharing what they already are trying in their own fields or supporting any aspect of the project. To discuss the possibilities, contact Brown at pjbrown@ucdavis.edu or (530) 752-4288.

The project includes research to ensure pollination, experiments to calculate irrigation needs amid water shortages, creating tools to improve public breeding programs, developing more efficient harvesting equipment, and economic analyses to ensure future pistachio cultivation is economically rewarding. Researchers hope to offer a guide for growers deciding whether to plant new orchards or remove existing ones.

“The success of California's pistachio industry, which is the top producer of the nuts in the world, has always relied on a strong collaboration between UC researchers and pistachio growers,” said project participant Florent Trouillas, a UC Cooperative Extension specialist in the UC Davis Department of Plant Pathology. “Research efforts must continue to address enduring and new challenges, improve sustainability and ensure the profitability of pistachio farming.”

Researchers will be looking for pistachio rootstock and cultivar combinations that have genetic predispositions toward tolerating warmer winters, less water and saltier soil. Photo by Pat J. Brown, UC Davis

The tasty, green nuts have blossomed into a $5.2-billion industry in California, thanks to their greater tolerance of dry lands and salty soils. The project aims to further improve their climate resilience by finding a rootstock that can thrive despite growing water scarcity and declining water quality projected over the next half-century. With millions of genetically distinct pistachio trees growing in the state, "we already have out there what may be the industry's next great rootstock," Brown said. "It's probably in some grower's field already. We just have to find it."

Researchers seek to pair that new rootstock with high-yielding scions – the producing part of the tree grafted onto the rootstock – to develop new combinations that can thrive in the different conditions across the state.

Trouble with “boy meets girl”

Pistachios, like many other tree crops, have male and female trees, and they require hundreds of hours of wintertime temperatures below 45 degrees Fahrenheit for the trees to flower in the spring. Wind blows the pollen from male flowers to female flowers, creating nuts.

Complicating the timing: Boy flowers and girl flowers generally require different amounts of winter cold to bloom. After a sufficiently cold winter, boys and girls flower together. But if the winter is warm, most of them will flower at different times, reducing pollination.

That happened in the winter of 2014-15, which saw unusually warm winter temperatures. The following fall, farmers harvested only half their expected crop, losing more than $1 billion, Brown said. Climate change is expected to provoke progressively warmer winters in the future, on average.

Male flowers and female flowers on pistachio trees generally require different amounts of winter cold to bloom. If the winter is warm, most of them will flower at different times, reducing pollination. Photo by Louise Ferguson, UC Davis

An additional complication: The boy scions come from a single variety, or cultivar, and the girl scions come from another single cultivar. "In California part of the problem is that we have been relying on a single male and single female cultivar," Brown explained.

A key part of this project will be to test new scions that can pollinate efficiently despite warmer winters. “We now have additional male and female scions released in the last 10 to 15 years, but we need more information on their chill requirements,” Brown said.

Growing importance of pistachio sector

With nearly 520,000 acres planted in California in 2021, pistachios are the fastest-growing tree nut crop in the state. Growers have doubled their plantings over the past decade, due to pistachios' drought tolerance and higher gross returns compared to other nuts, experts report. California dominates the industry, growing 99 percent of the nation's crop and nearly 60 percent of the world's crop, employing people in 47,000 full-time-equivalent jobs and creating $5.2-billion of total economic impact in 2020, according to American Pistachio Growers.

Brown's team is part of a wider effort at UC Davis to support the sector's growth and adaptation to climate change. Other department members participating in the project include co-directors Louise Ferguson, a UC Cooperative Extension pomologist, and Richard W. Michelmore, a distinguished professor and director of the UC Davis Genome Center. Also participating are Giulia Marino, a UC Cooperative Extension specialist; and Grey Monroe, an assistant professor.

Other UC Davis participants include Trouillas and Brittney Goodrich, a UC Cooperative Extension specialist in the Department of Agricultural and Resource Economics. The project also includes researchers from UC Merced, New Mexico State University and Purdue University.

The four-year project was among nearly $70 million in Specialty Crop Research Initiative grants awarded this fall by the National Institute of Food and Agriculture. The Department of Plant Sciences landed three of the 25 grants.

Read the NIFA grant summary.

Posted on Friday, December 16, 2022 at 9:42 AM
  • Author: Trina Kleist, UC Davis
Focus Area Tags: Agriculture, Food

Hotel refrigerators vary in temperature

Maureen Ladley
For food safety, storing leftovers at 33 F to 40 F is ideal

A few years ago, I was in Reno overnight for work and wanted to save my delicious dinner leftovers for breakfast. But when I opened the mini refrigerator in my room, my first reaction was, "That feels too warm!" I did not save the leftovers and made alternative plans for breakfast. Since then, I've wondered how common an unsafe hotel refrigerator might be.

The pandemic delayed my research as travel was out of the question for a while. This year, I had the opportunity to test my question when I traveled up the coast from California to Washington and back home again on vacation. I stayed in a variety of places, perfect for my casual research project. My trusty refrigerator thermometer came with me. The results: mixed!

Of the five hotels I stayed in:

  • One in-room refrigerator was too warm to store food safely overnight.
  • Two were too cold. One was so cold, it froze the beverage I placed inside. Not optimal, but better than food poisoning!
  • Two tested perfectly in the safe zone for food storage.

The score: One out of five refrigerators in my unscientific study was unsafe. One in five is not great odds.

The Ideal Refrigerator Temperature 

A temperature range of 33 F to 40 F is ideal. Refrigeration in this range slows the growth of microorganisms, including bacteria. Safe food-handling practices advise that food should be held for no more than two hours above 40 F. Keeping food overnight above that temperature could have serious consequences, meaning storing food in hotel refrigerators that are not 40o F or below for more than two hours can have serious consequences.

Refrigerator temperature ranges: what's safe and what's not safe?

Stay Safe When You Travel

Here are three ideas to help you avoid problems when you travel:

1)     Measure. Take a refrigerator thermometer with you if you plan to use the in-room mini refrigerator. There's nothing like data to let you know the refrigerator is at the right temperature. Refrigerator thermometers are readily available at grocery and hardware stores, and online.

2)     Avoid. Consider not storing anything that might spoil in your hotel refrigerator if you do not know the temperature setting. Cooling sealed canned beverages would be fine. At worst, your beverage will not be as cool as you hoped, but because it's sealed, nothing will spoil.

3)     Take a quality cooler. Since I was driving, I took my cooler, one that holds appropriate temperatures for days. Traveling with a ready supply of ice, beverages and confidence that my groceries were held safely below 40 F was lovely. This solution is not for every trip, and of course, you need to replenish the ice as you go.

As you plan your future travel, I wish you a safe journey and a skeptical mindset on the safety of your hotel refrigerator for food storage.

Do you have any questions about safe food storage? You can find your local UC Master Food Preserver program or submit questions at http://mfp.ucanr.edu. You can also sign up to be notified of upcoming online food preservation classes.

Posted on Monday, December 12, 2022 at 4:15 PM
  • UC Master Food Preserver of Solano/Yolo Counties: Maureen Ladley
Focus Area Tags: Food

Teaching Kitchen course helps improve college students’ food security

One approach to address food insecurity at UC Berkeley is a course on Personal Food Security and Wellness, with a Teaching Kitchen component that brings the lessons to life through knife skills, “no-cook” cooking, microwave cooking and sheet pan meals. Photo by Jim Block

Cooperative Extension researcher: Nutrition course a boon for UC Berkeley students

College students across the nation are struggling to meet their basic food needs. Within the University of California system of 280,000 students, 38% of undergraduate students and 20% of graduate students report food insecurity.

As part of the UC Global Food Initiative, in 2015 the Nutrition Policy Institute (a UC Agriculture and Natural Resources statewide research center) identified student food insecurity as a UC systemwide problem, prompting the UC Regents and campuses to collectively address the issue.

All 10 UC campuses now have on-site basic needs centers, providing food, emergency housing and support services. The UC system and campus working groups recognize that meeting basic needs, such as food, is a multidimensional challenge.

In response to the 2022 White House Conference on Hunger, Nutrition, and Health, which called for national efforts to reduce diet-related disease and food insecurity, UC renewed their commitment to cut the proportion of students facing food insecurity in half by 2030. Campuses will partner with local counties to maximize enrollment in the Supplemental Nutrition Assistance Program (also known as CalFresh in California), provide food for students who do not qualify for CalFresh, and allocate campus food resources to historically underserved student populations.

In evaluating the UC Berkeley course, Susana Matias, a Cooperative Extension specialist and collaborative researcher with the Nutrition Policy Institute, found a significant decrease in student food insecurity. Photo by Jim Block

NPI's collaborative researchers continue to monitor the impact of these efforts, in addition to other interventions, such as supporting students in building basic culinary skills, to improve food security. One multipronged approach to address food insecurity at UC Berkeley is a 14-week course on Personal Food Security and Wellness with a Teaching Kitchen laboratory component.

Sarah Minkow, who teaches the Personal Food Security and Wellness course at UC Berkeley, shared that students learn about nutrition and gain culinary skills through the Cal Teaching Kitchen.

The curriculum is designed with consideration for the time, cost and convenience of healthy eating. Discussions include food safety, calculating nutrient needs, mindful eating and reading nutrition labels. The Teaching Kitchen laboratory brings the lessons to life through knife skills, “no-cook” cooking, microwave cooking and sheet pan meals.

Minkow enthusiastically highlighted her students' “overwhelmingly positive [response to the] lecture and lab,” suggesting the benefits of an interactive learning environment to garner student engagement.

“Students often give feedback that they wish this was a required course for all UC Berkeley students,” said Minkow. She noted one barrier to reaching more students: capacity of the Teaching Kitchen space.

Susana Matias, a Cooperative Extension specialist at the UC Berkeley Department of Nutritional Sciences and Toxicology and collaborative researcher with the NPI, evaluated the impact of the Personal Food Security and Wellness course at UC Berkeley.

Matias reported that increasing food literacy and culinary skills among students has shown to increase intake of fruits and vegetables, and frequency of cooking, and reduce the number of skipped meals. Her study on the impact of the 14-week nutrition course also found a significant decrease in student food insecurity.

Across the UC System, students are benefiting from their campus Teaching Kitchens, including UC BerkeleyUC DavisUCLA and UC Riverside. Other campuses such as UC San DiegoUC San FranciscoUC Santa Cruz and UC Santa Barbara offer basic student cooking classes as well.

Katherine Lanca, UC Global Food Initiative fellow working with NPI, attended the 2022 Teaching Kitchen Research Conference as part of her fellowship to learn about the latest research on teaching kitchens supporting equitable health outcomes.

The conference was hosted at UCLA by Harvard T.H. Chan School of Public Health Department of Nutrition in association with the Teaching Kitchen Collaborative. Teaching kitchens are a promising approach to supporting food security and cultivating lifelong habits, especially among a college student population.

Posted on Monday, December 5, 2022 at 9:47 AM
  • Author: Katherine Lanca, UC Global Food Initiative Fellow, UC ANR Nutrition Policy Institute
Focus Area Tags: Food, Health, Innovation

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