Extreme weather spurred by climate change, including droughts and heavy rains, may increase the risk of nitrates from fertilizers ending up in groundwater, according to a recent study from researchers at the University of California, Davis. The study found heavy rains after a drought caused nitrates to seep 33 feet under farm fields in as little as 10 days. The study was published in Water Resources Research.
“The conventional wisdom was that it could take several weeks to years for nitrates to move from the crop root zones to reach groundwater,” said corresponding author Isaya Kisekka, a professor in the Departments of Land, Air and Water Resources and Biological and Agricultural Engineering. “We found these extreme events, such as California’s atmospheric rivers, are going to move nitrate more quickly.”
In this study, different methods were used to measure how much nitrate, a component of nitrogen fertilizer, was seeping down through the soil in a tomato and cucumber crop near Esparto, California. Scientists conducted their research from 2021 until 2023 when California was experiencing periods of drought followed by atmospheric rivers. They measured nitrate during both the growing seasons and the rainy seasons.
Drought can leave more nitrogen in soil
Previous studies have shown about 40% of nitrogen fertilizer used for vegetables isn’t absorbed by the plants but remains in the soil. During droughts, crops don’t use nitrogen efficiently, leading to excess nitrogen in the soil. This study found that if a drought is then followed by heavy rainfall, that sudden burst of water causes nitrate to seep in groundwater more quickly. The nitrate concentration in the shallow groundwater exceeded the U.S. Environmental Protection Agency maximum contaminant level of 10 milligrams per liter for drinking water.
“In California, we often say we swing between droughts and floods,” said Kisekka. “These extreme events that come with climate change are going to make the risk of these chemicals ending up in our drinking water much more severe.”
Groundwater is the primary source of drinking water for most of California’s Central Valley. In some regions, such as the Tulare Lake Basin, nearly one-third of drinking and irrigation wells exceed the EPA’s safe nitrate level. High nitrate levels in drinking water can increase health risks, especially for young children. It may also increase the risk of colorectal cancer.
Need for real-time soil nitrate monitoring
Central Valley farmers are required to report to the Regional Water Board how much nitrogen they applied to their field and how much was removed as part of the crop’s yield. The study compared different ways of monitoring when nitrate from fertilizers seep into groundwater. Kisekka said the results highlight the need for affordable, real-time soil nitrate monitoring tools to help farmers manage fertilizer use efficiently.
By using conservation practices that limit leftover nitrates in the crop’s root zone after harvest, farmers can help reduce nitrate contamination in groundwater.
This study’s data will also help improve a model called SWAT, which is used to track nitrate seepage into groundwater across California’s Central Valley. This effort is part of the Central Valley Water Board’s program to regulate irrigated farmlands.
Other UC Davis authors include Iael Raij Hoffman, Thomas Harter and Helen Dahlke.
The study was supported by the USDA Natural Resource Conservation Service through its Conservation Effects Assessment Project. The national project is designed to assess the effectiveness of conservation practices across different watersheds. The study also had support from the USDA National Institute of Food and Agriculture. — By Amy Quinton, UC Davis
The University of California, Davis, has reached new agreements to license more than a dozen of its world-renowned strawberry varieties to growers in countries across the world.
The agreements ensure that nurseries and fruit growers in Mexico, South America, Europe, Asia and the Middle East have access to all available varieties developed by the UC Davis Public Strawberry Breeding Program.
Strawberry plant varieties developed at UC Davis produce about 60% of all strawberries consumed around the world.
UK-based Global Plant Genetics, or GPG, will add 15 legacy varieties of UC Davis strawberry plants to its existing portfolio in China, South America, Europe, the Middle East and North Africa. GPG, which has been a UC Davis master licensee since 2018, already oversees licensing of a dozen of the more recently developed UC Davisvarieties in those markets.
Fresa Fortaleza, or F2, is the new master licensee for the legacy varieties in Mexico. Since 2020, the San Diego-based company has been the master licensee in Mexico for the more recently developed UC Davis varieties.
Earlier this year, UC Davis severed ties with former master licensee Eurosemillas as to these legacy varieties.
“We are pleased to have expanded our agreements with GPG and Fresa Forteleza,” said Helene Dillard, dean of the UC Davis College of Agricultural and Environmental Sciences. “We appreciate the shared commitment to maintaining outstanding relationships with our nurseries and growers and providing vigorous support for the UC Davis Public Strawberry Breeding Program.”
The new agreements cover:
The European Union, Switzerland and the United Kingdom
Argentina, Brazil, Chile, Colombia, Ecuador, Mexico, Peru and Uruguay
China
Egypt, Israel, Jordan, Morocco and Turkey.
The UC Davis Public Strawberry Breeding Program seeks to address the needs of growers by developing strawberries for positive characteristics including greater yield, flavor, disease resistance, and adaptation to different growing conditions. The university directly licenses strawberry varieties to nurseries in Canada and the U.S. and offers California strawberry growers a competitive advantage through exclusive access to new varieties for two years and reduced royalty rates.
The program, funded primarily by revenue from licensing strawberry varieties, also trains students and postdoctoral researchers to be leaders in the field.
Back in 2010, the UC Davis entomology labs of integrated pest management specialist Frank Zalom and molecular geneticist and physiologist Joanna Chiu joined forces to target the spotted-wing drosophila (SWD), a serious threat to berry production in California.
Drosophila suzukii,native tosoutheast Asia and first discovered in California in 2008, lays its eggs in such soft-skinned, ripening fruits as strawberries, raspberries, cherries, blueberries, peaches, nectarines, apricot and grape.
It packs a powerful economic impact. The first year of its discovery in California, the economic loss amounted to $500 million. Latest statistics from 2015 indicate a $700 million national economic loss.
The Zalom lab discovered the first SWD field populations with insecticide resistance in 2017. As the pest continues to spread throughout much of the country, anxious growers are worried about its increased resistance to pesticides.
The team’s newly published research in Scientific Reports is the first to characterize the molecular mechanisms of insecticide resistance in D. suzukii and provide insights into how current management practices can be optimized.
“In this work, we leveraged high throughput sequencing to identify biomarkers of insecticide resistance in D. suzukii,” Tabuloc explained. “We found that different genes are responsible for resistance to different chemicals. Specifically, we found that genes involved in metabolism are highly expressed in flies resistant to pyrethroid insecticides. We also observed evidence of two different mechanisms of resistance in 2 lines generated from a single spinosad-resistant population. We found an increased expression of metabolic genes in one line and increased expression of cuticular genes in the other.”
“Therefore, we developed a diagnostic panel using these biomarker genes to differentiate between pyrethroid resistance and spinosad resistance,” Tabuloc related. “Not only can our assay now inform whether there is resistance, it can tell us which chemical the population is resistant to and how severe the resistance is. Additionally, this method is faster, enables for the testing of more populations, and is more comprehensive as compared to bioassays, the conventional way of testing for resistance.”
Tabuloc added that “our work has enabled for the detection of resistance in California populations, and we are currently doing a nationwide screening to determine whether resistance is now present in other states. Currently, we are working with the Zalom lab to use the results of our assays to try and combat resistance. There are experiments in progress trying to increase the efficacy of insecticides by blocking some of the genes involved in resistance, such that the enzymes encoded by those genes have decreased function.”
Zalom, a UC Davis distinguished professor emeritus who directed the UC Statewide Integrated Pest Management Program for 16 years, said he has been “working on spotted-wing drosophila with Dr. Chiu and her lab members since she joined the UC Davis faculty in 2010, and it has been an absolute pleasure.”
Zalom, a past president of the 7000-member Entomological Society of America (ESA) and an elected Honorary Member, ESA’s highest honor, praised Chiu, a 2019-2024 Chancellor’s Fellow professor and now chair of the Department of Entomology and Nematology, as “one of the most collaborative researchers who I have ever worked with. When our lab found the first SWD field populations with insecticide resistance in 2017, it seemed obvious to ask Dr. Chiu about identifying the mechanism of resistance to different chemical classes and if it would be possible to develop a molecular diagnostic to confirm presence of insecticide resistance in field populations without conducting the time consuming and labor-intensive bioassays that we were using.”
“Dr. Chiu and her PhD student Christine Tabuloc took on this challenge and their work culminated in the description of genes associated with the resistance and the diagnostic assay presented in this paper,” Zalom said.
The Zalom lab “selected the SWD isolines from California field populations displaying resistance to pyrethroids and spinosyns after conducting bioassays on many hundreds of SWD adults, then helped Dr. Tabuloc validate results of the molecular assay,” he said.
“This work not only represents good science; it has very practical implications,” Zalom said. “Dr. Tabuloc and I presented results of the work from both of our labs at a special berry grower seminar on insecticide resistance organized by UC Agriculture and Natural Resources (UC ANR) Farm Advisor Mark Bolda in Watsonville. The presentations were extremely well-received. The original program was targeted for about 1.5 hours, but the meeting extended to over three hours due to the extent of questions and great discussion that followed. Growers and their consultants are hungry for new information that they find interesting and potentially useful, and this work was clearly of interest to them.”
Bolda, strawberry and caneberry farm advisor in Santa Cruz, Monterey and San Benito counties, “was the first person who found the insect and asked me to come down to look at it and the problem,” Zalom remembered. “That was 2008, and we weren’t able to get an actual species identification until 2009!”
Bolda noted that the recent berry grower meeting targeted SWD resistance on the Central Coast, with the UC Davis entomologists presenting. “The research was top shelf and the need, of course, is very great,” Bolda said. “Some of the information that Frank and Christine presented has been put into immediate use in the industry.”
“What made it really special was that since we were moving only a month or so later, and this was the last Extension meeting to be held at my UC Cooperative Extension Office,” Bolda said. “After 40 some years, that’s saying a lot and it was totally apropros that Frank, given his many, many years of service, was the very last to run a meeting there….and Christine presented also…she was really great and presented fabulous information.”
Among the “iconic individuals of Central Coast strawberries” who attended, Bolda said, was retired entomologist Ed Show (Driscoll Strawberry Association, Inc.) “who has been a part of strawberries since the 1970s.”
“It was nostalgic for me since it was the last meeting that was held there because they were moving to a new office,” Zalom said. “I must have done 80 presentations at that auditorium over the years, including some of the very first ones that I did when returning to California when I was doing research on brussels sprouts and apples in that area.”
Fruitville Collaboration. Professor Chiu said the publication “culminated years of fruitful collaboration and hard work by our lab and Professor Zalom’s lab, primarily driven by Christine…This research could not have been accomplished without Christine who is uniquely qualified to successfully lead the project; she combines her knowledge in insect genomics and bioinformatics with Drosophila molecular genetics.”
Chiu pointed out that “When the Zalom lab and my lab first started our collaboration in 2010, we were already worried about the potential development of insecticide resistance in D. suzukii given the primary method for management is insecticide application and the generation time of these flies are short. Unfortunately, this became a reality in 2017.”
“We hope that our research in developing more efficient molecular diagnostics to identify resistant populations will help prevent the spread of resistance to other U.S. states by allowing them to be proactive; perhaps to adjust their management program as soon as low level of resistance is detected,” Chiu said. “We are continuing to perform research to determine if resistance, once found, can be ‘weakened’ and what are mechanisms that could drive it. We think this will be very beneficial for growers in California, who currently have to tackle D. suzukiiwith insecticide resistance.”
Tabuloc, who joined the Chiu lab as an undergraduate research assistant in 2012, received her bachelor of science degree in biochemistry and molecular biology from UC Davis in 2015, and her doctorate from UC Davis in 2023.
In addition to Chiu, Zalom and Tabuloc, the 12-member team of researchers and co-authors included Curtis Carlson, Kyle Lewald, Sergio Hidalgo, Cindy Truong and Ching-Hsuan Chen, all from the Chiu lab; Nicole Nicola and Fatemeh Ganjisaffar of the Zalom lab; and Cera Jones and Ashfaq Sial of the Department of Entomology, University of Georgia, Athens. At the time, Truong and Chen were undergraduates, and Ganjisaffar was a postdoctoral fellow, and now a senior environmental scientist with the California Department of Food and Agriculture.
Federal and state grants awarded to Chiu and Zalom funded the project: a USDA National Institute of Food and Agriculture; and a California Department of Food and Agriculture Specialty Crop Block Grant. The team credits Bloomington Drosophila Stock Center for providing D. melanogaster stocks.
Facing a deluge of lower-price products from Europe, the California olive oil industry is doubling down on its clear-cut competitive edge: the consistent and bona fide quality of its oil.
“Olive Production Manual for Oil,” a new book published by University of California Agriculture and Natural Resources, aims to help California olive growers maximize that advantage.
“It’s a tough market to compete in, but I think the way to win for California is to compete on quality,” said book co-editor Selina Wang, a UC Cooperative Extension specialist in the UC Davis Department of Food Science and Technology. “The quality of California olive oil is unmatched, but you can’t make good quality olive oil with bad fruit, so the goal is to get more fruit from the trees – and for the fruits to be high-quality fruit.”
The 273-page manual, available for purchase online, is the first of its kind in the U.S. While some parts of the book are specific to California (which grows nearly all of the olives for domestically produced olive oil), most of the material would be useful to producers in other states, Wang noted.
“Through our conversations with growers, it became clear to us that a manual like this – not a scientific publication but a manual that is easy to follow, written in language that is accessible, and with pictures and illustrations – would be really helpful to the growers,” she said.
Growth of California olive oil industry necessitated creation of manual
The new oil olive production manual, published by UC ANR, is the first of its kind in the U.S. Copyright UC Regents
Aside from a book focused predominantly on table olives and another on organic olive production (by UCCE farm advisor emeritus Paul Vossen), there was no one-stop, comprehensive resource on the bookshelf for oil olive growers. The need for such a manual had become more acute as oil olives replaced table olives in California orchards during the last 20 years.
Whereas harvesting by hand was historically cost-prohibitive, the introduction of super-high-density planting systems in 1999 made oil olive production more economically feasible. Mechanical pruning and harvesting of new cultivars (Arbequina, Arbosana and Koroneiki) – specifically bred for these densely planted orchards – led to the rapid expansion of oil olives in the state. According to a U.S. Department of Agriculture report, California olive oil production jumped from 2 million pounds in 2006 to an average of 21 million pounds in 2021–23.
With about 37,000 acres of oil olives planted across California, the Olive Oil Commission of California saw the need to support the production of this manual. Championed by Dan Flynn, founder and executive director emeritus of the UC Davis Olive Center, Wang and co-editor Louise Fergusonoutlined the contents of the book. They then sought out a mix of growers and industry professionals and UCCE advisors and specialists to write its chapters.
“Most of the information is data-based, from people who are working with the olives,” said Ferguson, a UC Cooperative Extension pomologist at UC Davis. “This is the first data-based olive oil production manual we’ve had.”
Manual infused with firsthand insights, practical recommendations
Of the three main varieties planted in super-high-density systems, Arbosana has the most consistent fruit yield. Photo by Dan Flynn; copyright UC Regents
Hard-earned experience taught growers a valuable lesson that is conveyed in the book – the need to hand-prune. While mechanical pruning helps control the size of the trees, some hand-pruning is still required to allow light to filter to the leaves. Failing to do so leads to a dramatic decrease in yield.
“That happened in many of the orchards that were inexperienced in these new cultivars and new super-high-density planting systems,” Ferguson said.
She added that other key topics in the manual include irrigation management in a water-constrained state, nitrogen management, harvest timing and orchard site selection. Choosing a good spot for planting is crucial in this era of extreme climate volatility, Ferguson noted, as olive trees are significantly affected by temperature shocks in spring (fruit set) and fall (harvest).
For Wang, another overarching theme in the manual is the importance of testing. Testing the soil, water and leaves provides critical data that growers can use to adjust their inputs and production practices for optimal profitability.
“You may spend a couple hundred dollars on the lab work, but it will pay off, for sure – you’re going to increase the health and productivity of your trees,” Wang explained. “Oil olive growers are paid based on the oil content in their fruit; you not only want to have a lot of fruit on the trees, you want to make sure that your fruit are accumulating oil.”
California oil olive growers, practices continue to evolve
Wang and Ferguson hope their book will help California producers compete more effectively in the global marketplace. Currently, about 90% of the olive oil consumed in the U.S. is imported from Mediterranean countries, due primarily to the lower price point. In that region, producers tend to harvest riper olives that produce oil at a greater volume but lesser quality.
In contrast, California growers harvest earlier and produce oil that is higher quality (with more flavor and more antioxidants) and far exceeds accepted standards for “extra virgin olive oil.”
According to Wang, California olive oil mills have nearly maximized their efficiency, and the growth opportunity for the industry is in the orchards: to optimize practices to produce more fruit, and to plant more trees. Wang said the new manual can help on both fronts.
“Just like for other crops, focusing on quality – while increasing efficiency and productivity, and therefore profitability – is the name of the game,” she said.
Ferguson also stressed that knowledge continues to evolve and urged growers to reach out to the editors and chapter authors with their experiences.
“Most of the authors are in California and they’re working,” she said. “So if you start to notice things that are different, or you want more information or something is not clear, the authors are available.”
Inside a UC Davis engineering lab, tiny round pellets swirl in a brown liquid inside a 5-liter glass tank. The tank, a bioreactor, is brewing edible fungi high in protein and designed to look and taste like meat.
In another lab on campus, a liquid nitrogen tank nicknamed “cryocow” holds frozen vials of cow muscle stem cells. Scientists hope to one day turn these cells into lab-grown meat, creating the burgers of the future.
Researchers with the Integrative Center for Alternative Meat and Protein, or iCAMP, at UC Davis are leading projects like these to meet the world’s growing demand for meat in environmentally sustainable ways. Their goal is to identify alternative proteins that can be brought to market on a large scale. These proteins could come from fungi, plants, cultivated meat, or even innovative hybrids that combine conventional meat with alternative proteins.
Professor Ruihong Zhang in the Department of Biological and Agricultural Engineering is brewing the next generation of mycofood — food made from fungi in bioreactors. The fungi will soak up the colors and nutrients of whatever is in the bioreactor. (Jael Mackendorf/UC Davis)
The world’s demand for meat is expected to increase by at least 25%, and as much as 100%, by 2050, driven by a rising global population and an increasing appetite for meat in developing countries.
“Meeting that demand is not likely to happen just by growing more animals,” said David Block, director of iCAMP.
Producing meat also contributes significantly to global greenhouse gas emissions. But for alternative proteins to be widely accepted by consumers, scientists and marketers need to overcome significant challenges.
UC Davis is well positioned to provide the technology and knowledge needed to advance alternative proteins because of its interdisciplinary teams of researchers from the animal and food sciences, biological sciences, agricultural and chemical engineering and sensory sciences.
iCAMP brings those researchers together with industry experts and food innovators.
Researchers at UC Davis have created small balls of edible fungi that can be processed into products like boba and lab-grown caviar. Pictured are biological and agricultural engineering doctoral student Lin Cao and project lead and Professor Ruihong Zhang, Department of Biological and Agricultural Engineering. (Jael Mackendorf/UC Davis)
Mycofood: fungi of the future
Professor Ruihong Zhang in the Department of Biological and Agricultural Engineering is brewing the next generation of mycofood — food made from fungi in bioreactors.
She’s creating high-protein pellets from mycelium, the thread-like, branching parts of fungi. The fungi take on the color, flavor and nutrients of whatever they’re fed in the bioreactor. Zhang has fed them almond and walnut hulls, pistachio shells, carrots, tomatoes, red beets and even the byproducts of cheese-making.
“The fungi pellets will absorb bioactive compounds like antioxidants from almond hulls as well as the brown color,” Zhang said. “If fed tomato pomace, they’ll have a reddish brown color.”
The pellets can be transformed into all sorts of food. Zhang first used them to replace the tapioca balls in boba tea. She’s also made jerky from them. Dried pellets can also be ground into a powder to mix in other foods.
Zhang said she believes mycofoods, especially those made with agricultural byproducts like almond hulls, are more sustainable than animal or plant proteins.
“They’re a low cost, highly nutritious source of protein with a low carbon footprint,” Zhang said.
Her team’s work led to a startup company that’s now making fungal-based caviar, modeled after sturgeon roe. Optimized Foods uses the mycelium pellets to provide the structure of the roe and cultivated caviar, grown in a lab using sturgeon stem cells.
Mycoproteins and hybrid food
Making mycoproteins more widely available is the next step for companies already producing food from fungi. The Better Meat Co. of West Sacramento makes a mycelium protein called Rhiza. The company sells dehydrated white cubes of Rhiza to food producers to blend in plant-based foods or animal meat. Rhiza can also be eaten on its own.
“We know it’s not going to be possible to make everyone stop eating meat,” said Doni Curkendall, Better Meat’s executive vice president of business operations. “But we think you can make a small change, and for us, that means creating hybrid products.”
Hybrid products are growing in popularity, appealing to flexitarians, or part-time vegetarians. Research shows most people who eat plant-based meat alternatives also eat animal meat.
Rhiza mycoprotein is made by feeding fungi starchy foods through fermentation. This produces long fibers of mycelium, which are then drained or dehydrated, creating a product that has a meat-like structure and chewiness.
Currently, Better Meat produces Rhiza in a pilot plant. Curkendall hopes UC Davis’ iCAMP can help them scale up to commercial production.
“UC Davis has the expertise,” she said. “They have the facilities and people that can help us continue to do our research and continue to grow in this space.”
Curkendall envisions a time when Sacramento — known for being the farm-to-fork capital of California — will also be known as the fermentor-to-fork capital.
Madison Stewart, a graduate student researcher with the College of Biological Sciences, pulls out a nitrogen storage cylinder that holds vials of adult bovine muscle stem cells, which can be used as the starting material for cultivated meat. (Gregory Urquiaga/UC Davis)
Meat grown in a lab
Cultivated meat, or meat grown in a lab using animal stem cells, is the latest alternative protein. The U.S. Department of Agriculture approved its sale nationally in 2023, but it may not be available in grocery stores for years.
“We see cows grazing on grass and turning it into high-quality protein — meat,” said Anna Denicol, associate professor in the Department of Animal Science at UC Davis. “In the lab, we’re trying to replicate something that nature took thousands of years to perfect.”
Denicol is one of two UC Davis professors developing cow stem cells lines for cultivated beef. To make cultivated meat, cow stem cells are fed the right nutrients to help them grow and multiply. The cells also must differentiate into muscle cells, fat cells and connective tissue needed to make meat.
Scientists can use adult cow stem cells, but the problem with these cells is that they don’t duplicate forever, said Lucas Smith, assistant professor in the UC Davis Department of Neurobiology, Physiology and Behavior.
“The challenge is to expand them to greater degrees than you typically would in the body and then have them efficiently create muscle in a different environment,” Smith said.
Researchers can also use embryonic stem cells, which can replicate indefinitely in the right conditions. However, getting these cells to become the muscle, fat and connective tissue is much harder and takes longer.
The cultivated meat industry uses expensive, complex ingredients to keep cells alive, in a process borrowed from the biopharmaceutical industry. But food needs to be produced much more cheaply than pharmaceuticals. Also, the cells would need to grow in 250,000-liter fermentation tanks.
“The reality is that no one in the world has ever grown animal cells using more than a 25,000-liter fermentation tank. It’s still an open question whether it will work,” said Block, who is also a professor in the departments of chemical engineering and viticulture and enology.
UC Davis researchers, along with iCAMP and industry partners, are hoping to meet this challenge. Block said he remains hopeful that technological innovations could lead to widespread commercialization of cultivated meat.
“It’s probably 10 to 15 years away from being in all the supermarkets all across the country, but I am very optimistic that we’ll get there.”
David Block, director of the Integrative Center for Alternative Meat and Protein, or iCAMP, stands in front of giant fermentation tanks at UC Davis.(Karen Higgins / UC Davis)
Making meat substitutes taste like meat
Even with all the research and new technology, people might still be hesitant to buy alternative proteins. One big reason is the cost. Even the plant-based proteins on the market now are often more expensive than products made from cows, pigs or chickens.
Another challenge is making these alternatives have the taste, texture and mouthfeel of real meat. Soy and pea, the main ingredients in many plant-based proteins, can have off flavors that need to be masked, Block noted. They also need fat to give them the right mouthfeel and flavor.
But Block said part of the research mission of iCAMP is to determine what’s critical for consumers to buy these products.
“There is no projection that we’re going to need less meat,” Block said. “I would expect conventional animal agriculture may stay the same or even grow but these other methods of producing meat need to fill that supply gap.”
Donald A. Luvisi, UC Cooperative Extension viticulture advisor emeritus of Kern County, passed away in Bakersfield on July 10 at the age of 87.
Luvisi served as the viticulture farm advisor for Kern County from 1960 until his retirement 39 years later in 1999. He was widely recognized as a pioneer of the modern-day California table grape industry and his research influenced a significant expansion in the production of varieties such as ‘Flame Seedless,’ ‘Redglobe’ and ‘Crimson Seedless,’ along with improvements in fruit quality associated with his work with gibberellin, ethephon and girdling.
“He gave table grape growers the knowledge they needed to maximize packable yields by investigating and extending the nuanced production practices specific for each variety,” said Rhonda J. Smith, UCCE viticulture farm advisor emeritus.
Luvisi was widely regarded as an expert in postharvest handling of table grapes due to the impacts of his work on sulfur dioxide (SO2) fumigation. SO2 is used to inhibit the growth of fungi that can break down fruit in storage. In 1987, SO2 was removed from the ‘Generally Regarded As Safe’ (GRAS) listing by the U.S. Food and Drug Administration (FDA), and as a result, residue data and new application patterns had to be developed to prevent grapes from decaying in storage. Luvisi responded through his participation in more than 20 experiments annually that led to the acceptance of the “Total Utilization Fumigation” method and conversion of much of the industry to it from traditional fumigation. The restoration of newly approved postharvest SO2 fumigation methods was estimated to prevent 40%-50% losses in table grape production that at the time was valued at $200 million to $250 million.
The last decade of Luvisi’s career was focused on the evaluation of rootstocks for table grape production. These rootstocks were developed as a response to growers reporting replant problems in second- and third-generation vineyards due to the buildup of plant-parasitic nematodes in the soil. He conducted more than a dozen decade-long trials evaluating the performance of common table grape varieties on these rootstocks that led to guidelines for their use by local growers. The use of soil-borne pest resistant rootstocks has become an industry standard practice within the California table grape industry.
“Don was an internationally respected viticulturist, with particularly broad knowledge of table grape and wine production,” said Matthew Fidelibus,UCCE viticulture specialist. “He was also a generous and beloved colleague.”
Don Luvisi was not only an internationally respected viticulturist, “he was also a generous and beloved colleague,” said Matt Fidelibus, shown on left with Luvisi.
After retiring in 1999, Luvisi split his time between Bakersfield and Calistoga, where he managed a family vineyard. When in Bakersfield, he was generous with his time as a mentor to three subsequent UCCE Kern County viticulture advisors, and frequently met with his friends within the table grape industry.
In the early 2000s, he was highly influential in the development of the ‘General Beale Pilot Project’ that developed and tested area-wide management programs to control the glassy-winged sharpshooter, a vector of the potentially devastating Pierce’s disease of grapevines. His knowledge of the grape industry, combined with the personal relationships he had developed over a lifetime, proved invaluable in establishing this highly successful project that remains effective today.
Following his passing, former UCCE viticulture advisor Jennifer Hashim-Maguire said, “I’m forever grateful for having Don as a mentor and friend. His early tutelage at Cooperative Extension sowed the seeds of a career in table grape production that now spans decades and several countries.
“Luvisi’s passion for the advancement of the grape industry was contagious and unsurpassed. As a (wine) grower himself, he understood firsthand the challenges of farming and was eager and generous to share technical information and solutions with growers all over the world.
“Don’s legacy is measured not just in past research conducted and the growers he helped throughout his life, but in his kindness and the numerous relationships he cultivated in the industry from California to Australia, Chile to Greece and numerous places in-between,”Hashim-Maguire said. “The global table grape industry is an interconnected extended family and I know that I’m only one of many who will miss him deeply.”
Luvisi was an “exceptional mentor,” said Stephen Vasquez. From left, Allison Ferry-Albee, Ashraf El-kereamy, Luvisi and Vasquez.
Stephen Vasquez, a former UCCE viticulture advisor who served in Fresno County for 14 years, described Luvisi as an “exceptional mentor” who was always generous with his time and freely shared his knowledge, leaving a lasting impression on Vasquez who was a young viticulture plant pathologist in 1999.
“As a UC Davis plant pathology grad student working on grape diseases, Don would drive me around Kern County and show me areas with high incidences of grape diseases. We’d look at powdery mildew, measles, bunch and sour rots, etc. and talk about why they were problems in the vineyards we visited. The next time I was in town, Don would drive me around new vineyards and test my knowledge. Often, I would be stumped, and he’d explain the subtleties of the diseases. This scenario lasted for two summers, and I was grateful for the experience.
After completing his master’s degree, Vasquez applied for a viticulture farm advisor position in Fresno County. Luvisi was on the hiring committee along with several other viticulture farm advisors. “I was prepared to be grilled. Instead, he questioned me on grapevine disease scenarios with slight twists, which I had been trained to solve the past two summers. Don’s plan wasn’t to prepare me to be a farm advisor, he saw an opportunity to share his knowledge with someone who was interested in learning,” said Vasquez, who is now executive director of the Administrative Committee for Pistachios and looks for opportunities to share his knowledge with early career scientists.
Funeral services for Luvisi were held at St. Francis Church in Bakersfield on July 30 and burial on Aug. 1 at the Holy Cross Catholic Cemetery in St. Helena.
Those wishing to honor Luvisi’s life through contributions are encouraged to donate to the Don and Mickie Luvisi Agriculture Scholarship at Calistoga Junior/Senior High School. Donations to the scholarship fund can be made online at this link: https://www.convergepay.com/hosted-payments/?ssl_txn_auth_token=rc5FKo1YQV%2Bt0Vk%2F%2F5PGSQAAAY2E3mHg#!/payment-method. At checkout, specify “Scholarship” in the “Select Donation” field, then type in “Luvisi Scholarship” in the “Description” field.
Checks can be made to Calistoga Joint Unified School District with “Luvisi Scholarship Fund” in the memo line. Those can be mailed to 1520 Lake Street, Calistoga, CA 94515. For more information, please contact Carla Surber at csurber@calistogajusd.org. — By David Haviland & Pam Kan-Rice (UCANR)
Two of the worst pests plaguing lettuce growers in the Salinas Valley area are aphids, specifically lettuce-currant aphids (Nasovonia ribisnigri), and western flower thrips (Frankliniella occidentalis). Lettuce-currant aphid is an invasive pest that sets up shop in the heart of the lettuce plant and will render the crop unsellable when it reaches high enough numbers. Thrips can both cause cosmetic damage to lettuce crops and are also responsible for the spread of Salinas impatiens necrotic spot virus (INSV), the fatal lettuce disease that has driven large losses since the 2020 growing season.
While effective tools exist to control both aphids and thrips, they are almost exclusively chemical. Chemical sprays are increasingly under pressure due to changes in the regulatory framework in California as well as the development of pest resistance and discoveries of key chemistries in area watersheds1,2. The UC Davis FiVE lab biological control research program addresses a growing interest in developing alternative tools for managing both pests that do not rely on chemical applications. Biological control provides an opportunity for the management of thrips and aphids that do not rely on chemical tools.
Biological control is defined as the use of natural enemies to control a target pest. Three general categories of biological control could possibly be used as management practices for lettuce pests in the Salinas Valley area:
• Conservation biological control refers to the establishment and maintenance of resources and conditions favorable to a native or endemic beneficial species. Instead of releasing predators into crop fields, specific types of flowers and other habitats are planted to attract beneficial species that are already a part of the local ecosystem. To date, most efforts on biological control in lettuce have used the conservation biological control approach.
• Inundative biological control involves the release of a beneficial insect species in large numbers with the expectation that the beneficials that are released will only provide control for a short amount of time before eventually dying out. Such releases would need to be repeated at regular intervals for the duration of the growing cycle for a crop.
• Augmentative biological control refers to the use of releases of smaller numbers of beneficials to areas where a smaller population of the species already exists, but not in numbers great enough to provide adequate control of the targeted pest species. The goal of augmentative releases is to bolster already-existent populations of beneficial species so they achieve great enough numbers to provide control of the pest or pests of interest.
Conservation biological control in the Salinas Valley
Syrphid flies
Aphid pests of lettuce have been effectively managed in some lettuce production systems through the planting of sweet alyssum adjacent to and interspersed within crop fields3. Sweet alyssum is a favorite of the Syrphid fly (Diptera: Syrphidae), the primary biological control agent used to control aphid pests in lettuce. Syrphids, also called hoverflies or flower flies, are a family of black and yellow pigmented flies which resemble bees and stinging wasps. The coloration is a protective camouflage; Syrphid flies are harmless to humans. Syrphid adults are frequently seen visiting flowers for their nectar and pollen, which the insect consumes both as an energy source and to support their reproduction.
In exchange the female Syrphid flies will lay eggs in lettuce plants with lettuce aphid infestations, the primary food source for their young. Once the eggs hatch, the syrphid maggots, which are predatory on slow, soft-bodied insects, will feed on the aphids and suppress their population. Syrphid larvae are known to be voracious; some California species have been shown to consume upwards of 100 aphids per day4!
Syrphids are the intended beneficiaries of most conservation biological control in central coast lettuce fields, but other beneficial species take advantage of these resources as well.
Other predatory species love sweet alyssum
Many other biological control agents are supported by insectary plantings5. Ladybird beetles often inhabit lettuce fields and may provide some control of lettuce aphid infestations. Common lacewings (family Chrysopidae) are also found in lettuce fields and insectary plantings. Lacewings, which are only predatory in their immature or larval life stage, can provide biological control services against lettuce aphids and western flower thrips. Minute pirate bug (Orius sp.) and aphid midges (Aphidoletes aphidimyza) have also been observed in and collected from insectary plantings in lettuce fields, but it is not known the extent to which they can suppress populations of lettuce aphid or Western flower thrips.
UC Davis Fi-VE Bug IPM Lab biological control research programs
Including insectary plantings to attract naturally occurring predators has historically been the only efficient way to get beneficial species into crop fields. Newly developed technology using drones as a dispersal tool may provide another option for growers interested in using biological control as part of their pest management programs for aphids and thrips. This technology drastically reduces the time and labor required to conduct large releases of laboratory-reared beneficial insects, making the approach more feasible for growers.
As part of a research program funded by the California Department of Pesticide Regulation (CA DPR) and in collaboration with Daniel Hasegawa at USDA-ARS and with Parabug, we are studying the release of biological control agents using drones for the management of aphid and thrips pests of lettuce crops. Our three experimental programs are as follows:
In-field inundative releases of green lacewing larvae and predatory cucumeris mites to control aphids and thrips in lettuce
In-field drone release of green lacewing eggs and predatory mites
Experiments run by former Monterey County IPM Advisor Alejandro Del Pozo-Valdivia found that a single inundative release of green lacewing eggs (Chrysoperla rufilabris) in lettuce fields reduced aphid pressure six weeks after release6. Our experiment builds on Alejandro’s work, examining whether repeated releases of green lacewing eggs throughout the lettuce growing cycle reduce aphid numbers. Additionally, the experiment includes two treatments aimed at suppressing western flower thrips: inundative releases of a species of predatory mite (Amblyseius cucumeris), and a combined release of both predatory mites and green lacewing eggs.
Augmentative releases to bolster non-syrphid predatory species in insectary strips and intercropped alyssum
An insectary strip treated with an augmentative release of Orius insidious
Other native predators of aphids and thrips are present in the insectary plantings growers use to attract syrphids, but their numbers are too low to provide suppression of thrips and aphids in adjacent crops. These species are reared by commercial insectaries, but using them in an inundative release could prove too costly for growers. Experiments in this program examine the use of smaller releases of these predatory species early in the growing cycle over insectary plantings. The goal is to determine whether the presence of floral resources allows the predators to stick around and build up enough in population to control aphids and thrips in the crop field. Experiments will be conducted with aphid midge (Aphidoletes aphidimyza), an aphid predator, and minute pirate bug (Orius insidiosus), a predator of western flower thrips.
Augmentative releases to manage thrips in non-crop areas
Drone release of thrips predators over ice plant
Western flower thrips plague not just vegetable crop fields but also the vegetation surrounding crop areas. In this experiment, we will examine whether releases of cucumeris mites and minute pirate bugs over field edges planted with ice plant will establish these predators in the vegetation and provide long-term suppression of western flower thrips. — By Ian Grettenberger and Addie Abrams, UC Cooperative Extension
Citations
Deng, X. Study 321: Surface water monitoring for pesticides in agricultural areas in the Central Coast and southern California (2022)
Gao, Y., Lei, Z. & Reitz, S. R. Western flower thrips resistance to insecticides: detection, mechanisms and management strategies. Pest Manag. Sci.68, 1111–1121 (2012).
Brennan, E. B. Agronomic aspects of strip intercropping lettuce with alyssum for biological control of aphids. Biol. Control65, 302–311 (2013).
Hopper, J. V., Nelson, E. H., Daane, K. M. & Mills, N. J. Growth, development and consumption by four syrphid species associated with the lettuce aphid, Nasonovia ribisnigri, in California. Biol. Control58, 271–276 (2011).
Bugg, R. L., Colfer, R. G., Chaney, W. E., Smith, H. A. & Cannon, J. Flower Flies (Syrphidae) and Other Biological Control Agents for Aphids in Vegetable Crops. (University of California, Agriculture and Natural Resources, 2008). doi:10.3733/ucanr.8285.
Del Pozo-Valdivia, A. I., Morgan, E. & Bennett, C. In-Field Evaluation of Drone-Released Lacewings for Aphid Control in California Organic Lettuce. J. Econ. Entomol.114, 1882–1888 (2021).
Applications are due on April 17 for Class 54 of the California Agricultural Leadership Program. Applicants should be mid-career growers, farmers, ranchers, horticulturalists, foresters and/or individuals working in other areas of California’s diverse agriculture industry.
For links to the application, informational resources and upcoming prospective applicant events, visit www.agleaders.org/class54apply/.
The Ag Leadership Program, operated by the California Agricultural Leadership Foundation (CALF), is considered to be one of the premier leadership development experiences in the United States. Through the program, fellows learn leadership skills that help them expand their impact. More than 1,400 individuals have participated in the program and are influential leaders and active volunteers in agriculture, communities, government, business and other areas.
Over the course of the intensive 17-month program, fellows are immersed in numerous topics, including leadership theory, effective communication, motivation, critical thinking, change management, emotional intelligence and other skills and tools that contribute to improved performance. Along with individualized leadership development coaching, fellows engage in situations and discussions focused on complex social and cultural issues. They are provided with opportunities to build enhanced critical thinking skills that, combined with a broader perspective, help graduates guide creative solutions throughout their lives.
The program includes approximately 55 days of formal program activities. Four partner universities — Cal Poly Pomona, Cal Poly San Luis Obispo, Fresno State and UC Davis — deliver integrated, comprehensive and diverse curriculum at the seminars. Fellows learn from first-rate educators and subject authorities from many professions and backgrounds. As a valuable extension to the monthly seminars, fellows participate in national and international travel seminars that provide further opportunities to understand interconnected systems and governments, dialogue with policy leaders and compare and contrast cultural dynamics.
Not all cattle are the same when it comes to grazing. Some like to wander while others prefer to stay close to water and rest areas.
Recognizing those personality differences could help ranchers select herds that best meet grazing needs on rangelands, leading to better animal health and environmental conditions, according to a new paper from the University of California, Davis, published in the journal Applied Animal Behaviour Science.
“Cattle can actually be beneficial for the rangelands,” said lead author Maggie Creamer, who recently earned her Ph.D. in animal behavior at UC Davis. “Vegetation in rangelands actually need these kinds of disturbances like grazing.”
Ranchers can add elements to the rangeland such as water, mineral supplements and fencing to influence where cattle graze, but little research has been done on how those efforts affect individual cows. Considering personalities could save money.
“If you’re spending all this money to add a management tool in order to change the distribution of your animals, that’s a huge cost to ranchers,” said Creamer. “Thinking about other tools, or selecting certain animals with these grazing traits, might be a better way to optimize the distribution on rangeland rather than spending a bunch of money for something that may ultimately not pan out for all your animals.”
Effects of grazing
Livestock graze on an estimated 56 million acres in California, and healthy rangelands host native vegetation and animals, foster nutrient cycling and support carbon sequestration.
Uneven grazing can degrade water quality, soil health and habitats. Optimizing grazing — including the even spread of cow pies — can improve the ecosystem while also reducing fuel loads for wildfires.
To better understand individual grazing patterns, researchers went to the UC Sierra Foothill Research and Extension Center in Browns Valley and tracked 50 pregnant Angus and Hereford beef cows fitted with GPS collars.
The research
The cattle, which were tracked from June to August over two years, had access to 625 acres of grasslands and treed areas ranging in elevation from 600 to 2,028 feet. In the second year, a new watering site was added at a higher elevation.
Across the two years, the cows showed consistent and distinct grazing patterns even when water sources changed. Age and stage of pregnancy did not affect patterns, though cattle tended to clump near water and rest sites on hotter days.
The cows that ventured into higher elevations and farther from watering sites had more variability in their grazing patterns than those that stayed at lower elevations near water. That suggests it may be harder for non-wanderers to adjust to some landscapes.
“Thinking about the topography of your rangeland and your herd of cows can benefit both the animals and the sustainability of the land,” said Creamer, who next month begins work as a postdoctoral scholar in North Carolina.
Gauging personalities
Keying in on personality type may sound difficult, but the researchers also found some clues as to how to pinpoint the wanderers and homebodies. Unlike cattle at feedlots, the breeding cow population, especially on rangelands in California and other western states, live largely “wild” lives and are rarely handled, save for vaccinations and weaning.
Research due to be published later this year found that paying attention to individual cow reactions during those events can help determine personalities. The cows that appeared more passive during those handling interactions tended to be nomadic.
“We found that you can maybe predict those hill climbers if you kind of look at how they act when the veterinarian or rancher handle them,” said senior author Kristina Horback, an associate professor in the Department of Animal Science at UC Davis.
Informing practices
For ranchers, the findings could be invaluable, said Dan Macon, a livestock and natural resources Cooperative Extension advisor in Placer and Nevada counties for UC Agriculture and Natural Resources.
“Any time we can improve our understanding of cattle behavior, particularly at the individual level, it can improve how we handle livestock and manage the landscape,” he said.
Macon said that during the recent drought, it was hard to get cattle into higher country, but if ranchers could have selected the nomads, it may have saved money in terms of ranch labor and other efforts.
“If you ask a rancher who has been attentive to their cattle over many years, they know the personalities,” Macon said.
For Creamer and Horback, the research opens new doors into understanding herd behavior and dynamics, one that could be a cheaper alternative to high-tech solutions.
“Animal science tends to look overlook the mind of the animal when searching for solutions to challenges,” Horback said. “It’s always been a direct line to genetics for immunity or nutrition, but nothing about the mind of the animal. And that’s such a loss. There’s so much we can learn from behavior in the end.”
The Russell L. Rustici Rangeland and Cattle Research Endowment supported the research. — By Emily C. Dooley, UC Davis
To manage johnsongrass, a noxious weed that crowds out cotton and sickens horses, farmers have tried herbicides, burning and hand-pulling. Now, researchers in the UC Davis Department of Plant Sciences have developed a more high-tech weapon against the invasive weed: artificial intelligence and machine learning.
Using photos from Google’s Street View database, the researchers have tracked down more than 2,000 cases of johnsongrass in the Western United States for a fraction of the cost and time that it would take for drive-by or other in-person surveys. They call their tool Google Weed View.
Johnsongrass identified growing near agricultural land using Google Street View. The yellow boxes were designated by artificial intelligence; the red boxes were drawn by human hand. (Mohsen Mesgaran/UC Davis)
The advancement could help land managers easily and quickly survey for other problem plants.
“Once the model is trained, you can just go and run it on millions of images from Google Street View,” said Mohsen Mesgaran, an assistant professor in the department. “We have huge flexibility, and its capability can be scaled up very quickly.”
The technique can easily be extended to other plant species. All that is needed is to label the new item in Street View photos and train the algorithm to identify that object in the images.
By providing location information, Google Weed View also offers an opportunity to examine how climate affects the growth and spread of weeds and invasive plants at very large scales.
“I think it can be both useful for management and for people with interests in more basic questions in ecology,” Mesgaran said.
Johnsongrass, far left, captured near a construction site using Google Street View. (Mohsen Mesgaran/UC Davis)
A colleague’s query
Mesgaran began looking at Google’s photo database of roadways, streets and highways after Kassim Al-Khatib, a professor of Cooperative Extension in the same department, asked if he could survey Western states for johnsongrass.
Al-Khatib studies where johnsongrass grows, ways to manage it and how this perennial has evolved to be so prevalent and resilient. He’s also working with scientists at the University of Georgia to decode the genome of johnsongrass, which is one of the top 10 most invasive weeds worldwide.
Johnsongrass can crowd out native plants, harbor pathogens and affect agriculture. It grows up to 7 feet tall with flowers that are green, violet, dark red or purplish brown depending on maturity, according to a UC Statewide Integrated Pest Management Program briefing page.
“Johnsongrass is a major weed not just in California but worldwide,” Al-Khatib said. “It’s very difficult to control. It’s a problem on vineyards. It’s a problem for cultivated crops. It’s a problem on orchards.”
Google Weed View allows for rapid, convenient scanning. It is continuously updated via everyday users with compatible cameras and images collected by Google. “Instead of a day of in-person driving, we can use AI to determine if johnsongrass is in a county or not,” Al-Khatib said.
Setting the parameters
To find the weeds, Mesgaran went to Google Street View, which hosts billions of panoramic photos. It didn’t take long to find johnsongrass.
“The pictures are really good quality,” he said. “You can see plants and flowers.”
Street View’s photos offer a 360-degree view, so in his request, Mesgaran set parameters, based on street direction (bearing), to only see the side view. He also specified latitude, longitude and other factors. To train the deep, or machine learning, model, he chose Texas, where johnsongrass is prevalent.
A student sorted through more than 20,000 images from that request to find pictures with johnsongrass, then drew rectangular shapes around the weeds. They located 1,000 images.
The labeled photos were fed into a computer to train a deep learning algorithm capable of identifying johnsongrass in Google’s images. The model was run again to capture potentially more images containing johnsongrass. These additional images were then labeled and used to further refine the model. With each iteration, the algorithm learned and became more accurate.
“This deep learning model was trained by these images,” Mesgaran said. “Once we had a semi-working model, we ran it against about 300,000 images.”
For Al-Khatib’s request, researchers focused on 84,000 miles of main roads in California, Nevada, Oregon and Washington states. The team discovered 2,000 locations with johnsongrass.
Google Weed View cost less than $2,000 to purchase the images and teach the model. A traditional car survey to cover the same area would cost an estimated $40,000 in gas, hotel, food and other costs.
“In a matter of months, we came up with 2,000 records, and I can do it for the whole U.S.,” Mesgaran said.
Next up? The whole United States. — By Emily Dooley, UCANR
