California Fruit and Vegetable

Tag: UC Davis

  • New Avocado Study Outlines Costs & Returns of High-Density Plantings

    Growers considering producing avocados in San Diego County with high-density plantings now have help to determine the economic feasibility. A new study on the costs and returns of establishing and producing avocados in San Diego County has been released by UC Agriculture and Natural Resources’ Cooperative Extension, UC Agricultural Issues Center and the UC Davis Department of Agricultural and Resource Economics.

    A worker prunes weak tree branches to improve sunlight penetration in a high-density avocado orchard.

    Avocado has been one of the prominent crops produced in Southern California since the early 1950s. California avocado production peaked in 1987-88 with about 76,300 acres. San Diego had been the leading producer accounting for about 60% of the acreage.

    “Beginning in the early 1980s, there has been a continuous decline of acreage and production of avocados in San Diego County, said Etaferahu Takele, UC Cooperative Extension farm management advisor for Southern California and co-author of the study. “This is mainly because of the expansion of urban development that has increased the cost of producing the crop and especially the cost of water, reaching to up to $2,000 per acre feet in 2020.”

    The same amount of water was sufficient for the high-density avocados as it was for the traditional planting (Photo by Gary Bender).

    High-density planting increases profitability of avocado production given there is suitable land for high-density orchard development.

    Although the cost of water accounts for 44% of the total production cost in the high-density planting, the water cost is proportionally less than in the conventional planting of 145 trees per acre when distributed over a higher yield per acre, the authors write.

    Their cost analysis describes production operations for avocados planted at 430 trees per acre, with an expected life span of 40 years. The study includes a detailed summary of costs and returns and a profitability analysis of gross margin, economic profit and a break-even ranging analysis table, which shows profits over a range of prices and yields. Growers can identify their gross margin and returns to management based on their yield and prices received.

    UC Cooperative Extension advisor Gary Bender checks sunlight penetration in a high-density avocado orchard.

    Input and reviews were provided by a UC Cooperative Extension farm advisor and grower cooperators in San Diego County. The authors describe the assumptions used to identify current costs for avocado establishment and production, material inputs, cash and non-cash overhead.

    The new study, “Avocado Establishment and Production Costs and Profitability Analysis in High Density Planting, San Diego County-2020,” can be downloaded for free from the UC Davis Department of Agricultural and Resource Economics website at http://coststudies.ucdavis.edu and UCCE Riverside County Farm Management website at https://ucanr.edu/sites/Farm_Management/Costs_and_Returns. Sample cost of production studies for many other commodities are also available on the websites.

    For additional information or an explanation of the calculations used in the studies, refer to the “Assumptions” section of the report or contact Takele at (951) 683-6491 Ext. 243 or ettakele@ucanr.edu or Donald Stewart at the UC Agricultural Issues Center at destewart@ucdavis.edu. — By Pamela Kan-Rice, UCANR

  • Root Bacteria Could Help Defeat Fatal Citrus Disease

    A UC Riverside-led team is looking at tiny underground microorganisms for a way to prevent a huge problem — Huanglongbing, a disease with no cure that has decimated citrus orchards worldwide.

    The disease, also known as HLB or citrus greening, has multiple names but the same ultimate result: bitter and worthless citrus fruits. By some estimates, the end of citrus orchards in California and Florida could amount to $14 billion in lost commercial revenue.

    Fruit affected by Huanglongbing. (UCR)

    “Often times, it is thought of as an above-ground disease of the fruits, leaves, and stems,” said Caroline Roper, plant pathology professor and director of the new research effort. “However, we have seen the roots of trees decline with infection, and we want to understand why.”

    The National Institute of Food and Agriculture has awarded the UCR-led team $10 million over the next five years to investigate the role of soil and root microbes in the disease.

    Roper said data from previous studies shows the microbiome of the infected tree — which includes bacteria and fungi as well as protozoa and viruses — plays a role in the disease.

    “We have seen a shift in the root microbiome as trees get sicker,” she said.

    The microbiomes shift to contain more potentially parasitic organisms that may act as secondary invaders to a tree that is suffering from HLB, according to Roper. The invasion of these root pathogens may be causing trees to die faster when they have HLB.

    Part of this new research effort will test whether soil amendments like manure and compost might suppress parasitic microorganisms in the roots as well as the soil, and give the trees more strength to combat diseases including HLB.

    In addition, the research team will try to determine the molecular basis of HLB resistance shown by citrus root stocks developed in Florida. They’ll then see how those rootstocks perform in California, which has different soil and climate conditions.

    The research team will examine both younger trees, because a lot of citrus growers have had to re-plant their orchards after infection, as well as older trees to see if mature groves can recover.

    It will also be important to note how well root stocks from Florida, where there has been a heavy infestation of HLB, perform in California, where much less of the disease has been detected.

    “One of the great things about this grant is that we’re able to leverage existing field trials being done by our collaborators in Florida and at the UC’s Lindcove Research and Extension Center in central California,” Roper said. “This may lead to faster results than we’d otherwise have had.”

    Collaborators on the project include UC Davis; California State University, Sacramento; the University of Florida; and the U.S. Department of Agriculture’s Agricultural Research Service in Ft. Pierce, Florida. — By Jules Bernstein, UC Riverside

  • Assessing the Costs & Benefits of Winter Cover Cropping in CA

    Winter cover cropping is a promising agricultural management practice that boosts soil health. This article discusses a benefit-cost analysis of winter cover crop adoption and introduces a web-based interactive calculator for farmers to assess changes to baseline farm profits.

    Winter cover cropping is an agricultural management practice that can enhance soil health while protecting fields from soil erosion and compaction. Cover crops are typically grown on farmland that would otherwise be left fallow in the wintertime, such as fields used for annual spring-summer crops, or in between rows of trees or vines, and thus do not replace a cash crop. Despite its well-known soil health and ecological benefits, and popularity in other parts of the U.S., winter cover crop adoption rates are low across California’s specialty crops. To better understand drivers and incentives for adoption, we created a benefit-cost calculator that estimates how baseline profits change as a farmer integrates winter cover cropping.

    This tool was designed for specialty-crop farmers who are interested in growing winter cover crops and want to understand how long it will take for that investment to break even. However, the tool is useful for anyone interested in better understanding the financial implications of cover cropping. In this article, we explain the methodology behind the tool and how to use it.

    Methodology

    We developed a calculator that estimates the expected changes in expenses and revenues associated with the introduction of winter cover cropping for a given farming operation. We started by modeling the implications of winter cover crops to average farms that grow processing tomatoes and almonds, two of California’s most important agricultural commodities. The model estimates a benefit-cost ratio in present value terms, i.e., the ratio of the sum of benefits over the sum of costs accumulated over time and discounted to the present.

    In our baseline analysis, we considered cover crop seed mixes that are commonly used for winter cover cropping in California’s Central Valley. For tomato operations, this was assumed to be a small grain forage mix (e.g., bell beans, winter peas, common vetch) and for almonds, this was assumed to be a more expensive clover mix.

    Table 1 lists potential benefits and costs of winter cover cropping. Benefits and costs are not the same every year. The monetary values for each of these components are incorporated into the model at the specific time when that benefit or cost is likely to be experienced.

    Benefits include increased income from greater yields, which results from improvements in soil quality, fertility, and soil-water relations due to cover cropping. Benefits also include reductions in expenses associated with soil erosion control, nutrient cycling, weed control, mycorrhizal fungi colonization, and reduced tillage operations. Almond growers may also benefit from lower beehive prices.

    The potential for cover crops to affect the irrigation requirements of cash crops is debated in the scientific literature. Cover crops may lead to higher water infiltration (resulting from improved porosity of the top soil), which can lead to increased capture of winter and spring rainfall, increased soil-water storage, which in turn can delay irrigation start and eventually reduce spring/summer irrigation requirements slightly; however, these effects are soil-specific and difficult to quantify and generalize and, thus, are not included in the baseline model. Other potentially valuable aspects of cover cropping that were not explicitly accounted for in the analysis include reduced soil sealing and compaction, better soil oxygen concentration and diffusion rates, as well as increased effectiveness of salt-leaching practices.

    Furthermore, while cover cropping has been shown to improve ecosystem services and downstream user benefits, these are not included in the baseline benefit-cost calculations. These societal benefits, which include increased soil organic matter, the protection of downstream surface water quality via reduced runoff, and carbon sequestration through enhanced soil-carbon storage, were not included because they would not accrue as a revenue flow to the farmer choosing to adopt.

    Costs include the initial expenses associated with cover crop seeds, planting, and termination, depreciation of machinery used for this management practice, and time spent learning how to incorporate cover crops into an operation, as well as disseminating new instructions to crewmembers. The model accounts for financial losses due to potential harvest complications with cash crops. For example, a heavy rain at the end of March could delay termination of cover crops, and thus delay the planting of tomato seedlings, which can postpone the timing of tomato harvest. This poses a potential complication for farmers who contract with tomato canneries, resulting in penalties.

    To quantify these benefits and costs, we collected data from UC Ag Issues Center’s Cost and Return Studies, scientific publications, semi-structured farmer interviews, and field experiments to establish an average value of each benefit and cost component. We then aggregated these components to estimate benefit-cost ratios for tomato and almond production systems, where a value of the ratio greater than 1 indicates a net positive change in profits. The interactive calculator is seeded with the average value for each benefit and cost component, but can be adjusted by the user to reflect a specific farming operation. While our model attempts to be as comprehensive as possible, some potential benefits or costs are not included, such as interactions with pruning or other practices.

    Results

    When using average values for all the benefit and cost components, we find that almond systems have a benefit-cost ratio greater than 1 when considering a 30-year time horizon, meaning that benefits are likely to exceed costs on average. When using average values for the tomato system, we find the benefit-cost ratio to be less than 1, given their assumed 10-year time horizon. The time horizons of 10 and 30 years were chosen for tomato and almond operations, respectively, to reflect typical rotation patterns and crop life cycles. Figure 1 displays these results year-over-year. At the 10-year mark for tomatoes and the 30-year mark for almonds, the average benefit-cost ratios are 0.5 and 1.3, respectively, indicating that total benefits eventually outweigh total costs for almond operations, but not tomatoes.

    Winter cover cropping is an investment in the long-term viability of agricultural operations. The benefits and costs accrue differently over time and may vary from year to year. Harvest complications with a cash crop reduce profitability but can be avoided with flexible contractual obligations or by growing a cover crop with predictable senescence. Overall, our results show the value of this soil management practice is greatest for California farmers with a longer time horizon and willingness to manage a cover crop as carefully as their cash crop.

    Interactive Web-based Calculator

    The web-based cover crop calculator, partially shown in Figure 2 and available here, is an interactive decision-support tool that calculates the benefits and costs of winter cover cropping in almond and processing tomato operations. The tool estimates how much farmers can expect their profits to change after growing winter cover crops for a certain number of years. All values used in the calculator are flexible and can be adjusted to match the reality on any commercial farm. The calculator is seeded with the average values for each cost and benefit component that we considered, but the user can easily adjust or remove any component.

    The calculator assumes continuous cover cropping after the year of adoption (first year), and that all benefits of cover crops begin accruing within the first five years. Importantly, the tool may not capture every potential benefit and cost from introducing cover crops into a farming operation. It simply serves as a guide to when a farm can expect to experience economic returns, based on the monetized benefits and costs.

    As mentioned previously, cover crops could either increase or decrease spring-summer irrigation requirements. Although this component is not included in the baseline net present value model, the calculator is flexible in this variable. The user can specify the extent to which cover crops increase or decrease irrigation requirements in the growing season and can add irrigation costs to germinate the crop if needed, and then observe how their baseline profits shift accordingly. Users can also explore how a financial incentive, in the form of an annual subsidy payment per acre of cover-cropped farmland, will affect their outcomes. The calculator allows one to value the social benefits of cover cropping (ecosystem services, carbon sequestration, and downstream water quality) via this subsidy component. – By Ellen Bruno, Alyssa DeVincentis, Samuel Sandoval Solis, and Daniele Zaccaria, UC Giannini Foundation of Agricultural Economics, University of California

    Authors’ Bios

    Ellen Bruno is an assistant Cooperative Extension specialist in the ARE department at UC Berkeley. Alyssa DeVincentis is a Ph.D graduate from UC Davis in Hydrologic Sciences. Samuel Sandoval Solis is an associate professor and Cooperative Extension specialist and Daniele Zaccaria is an associate Cooperative Extension specialist, both in the Department of Land, Air and Water Resources at UC Davis. They can be reached at ebruno@berkeley.edu, ajdevincentis@ucdavis.edu, samsandoval@ucdavis.edu, and dzaccaria@ucdavis.edu, respectively. 

  • Study Verifies Low Food-Safety Risk at CA Farmers Markets

    A new study by University of California, Davis, researchers finds a low risk of contamination of foodborne pathogens on produce and meat at Northern California certified farmers markets, but still finds cause for some concern.

    The study, published in the Journal of Food Protection, examined the prevalence of Salmonella on meat and produce, as well as the prevalence of generic E. coli on produce. Samples were taken from 44 certified Northern California farmers markets, including in the Sacramento region and Bay Area. Less than 2 percent (1.8 percent) of animal products sampled, including beef, pork and poultry, tested positive for Salmonella, while all produce samples tested negative. Slightly more than 30 percent (31.3 percent) of produce tested positive for generic E. coli. Generic E. coli is an indication of fecal contamination, but not all E. coli is harmful. This study didn’t test for pathogenic E. coli.

    “Based on this data, I think it’s safe to consume meat and produce from farmers markets,” said lead author Alda Pires, a UC Cooperative Extension specialist and research scientist in the UC Davis School of Veterinary Medicine. “That’s a low risk of contamination of foodborne pathogens, especially Salmonella.”

    While the prevalence of generic E. coli may seem relatively high, the concentrations were low. Pires said that’s especially so compared to previous studies of contamination at farmers markets elsewhere in the United States. The prevalence of Salmonella in meat sampled from Northern California farmers markets is also much lower than what previous studies have found in grocery stores.

    Among the produce sampled, leafy greens had the highest prevalence of E. coli, followed by root vegetables.

    Consumers should still be cautious

    Consumers and farmers should still be aware that produce and meat were not free from contamination. Consumers need to make sure the foods they prepare from farmers markets follow the good hygiene practices recommended by Centers for Disease Control and Prevention. Consumers should also keep produce separate from meat to avoid cross-contamination. 

    “The study raises awareness that it’s not just very large farms that can have contamination,” said co-author Michele Jay-Russell, with the Western Center for Food Safety at UC Davis. “Farmers need to pay attention to everything they’re doing, from planting to storage, to avoid contamination.”

    While certified farmers markets are inspected for food hygiene, microbiological quality is not explored. Smaller farms, those making less than $25,000 a year, are also exempt from certain food-safety provisions of the U.S. Food and Drug Administration’s Food Safety and Modernization Act. Foodborne illness costs the U.S. economy more than $15 billion annually.

    Other co-authors include James Stover, Esther Kukielka, Viktoria Haghani, Peiman Aminabadi and Thais De Melo Ramos of UC Davis. Research support came from the U.S. Department of Agriculture. — By Amy Quinton, UC Davis

  • Pythium & INSV Infections in Salinas Lettuce Fields

    In 2020 the incidence of Pythium wilt (caused by Pythium uncinulatum) of lettuce has increased in severity and in the number of affected fields. Pythium infections in lettuce fields have been observed frequently, but not always, occurring with INSV infection. As a result, there has been confusion distinguishing between these two diseases and the role of each of them in causing the problems in fields. In this blog we will discuss these two diseases and explain from our current state of knowledge about the disease dynamics occurring in affected fields.

     INSV has been a production problem on lettuce in the Salinas and surrounding valleys for a number of years and in 2020 it continues to be a serious production issue. Pythium wilt of lettuce is a relatively new problem and was first discussed in a blog entry in October 2015 by Steve Koike (https://ucanr.edu/blogs/blogcore/postdetail.cfm?postnum=19327 ). However, in 2019 and 2020 we have seen an increase in the number of acres affected by Pythium wilt as well as the severity within fields. Given that Pythium is a relatively new problem and the extent of the problem suddenly increased, some growers and PCAs are confronting this problem for the first time. To add to the confusion, at times INSV and Pythium infections are occurring together on the same plants which has caused confusion and has led to much speculation about the role of each disease in the observed damage.

    Symptoms of INSV

    Issues with INSV infections on head and leaf lettuce types are not a new occurrence in the Salinas Valley and many growers and PCAs are familiar with the symptoms and the patterns of infection in the field, especially on romaine. In general, INSV on lettuce causes characteristic patterns of chlorosis and necrosis on the inner leaves of the plant, as well as significant stunting (Photo 1). However, INSV can cause significant necrosis and lesions on and at the base of the ribs of lettuce plants (Photo 2). It should be mentioned that Tomato Bushy stunt virus (TBSV) can cause symptoms that can be confused with INSV and Pythium wilt; however, lettuce dieback symptoms are always seen on the outer, older leaves and the TBSV pathogen is commonly restricted to low-lying areas along the river. In addition, head lettuce varieties and some romaine varieties are resistant to this virus. When in doubt, it is important to have a sample tested. That said, INSV is the overwhelming virus issue facing growers and PCAs in 2020.

    Moderate to severe symptoms of INSV on ribs of romaine.

    Viral vs. Fungal Symptoms

    One important detail about lettuce plants infected with only INSV is that they do not exhibit wilting of the outer leaves of the plant or show root rot or root discoloration. This is important to note because in 2019 and 2020 we have visited many fields where the plants exhibit symptoms of INSV and have wilting older leaves. In these situations,  the roots and crowns of the plants should be examined for symptoms caused by soilborne pathogens such as the wilt pathogens (Fusarium and Verticillium), Sclerotinia, and Pythium. Fusarium and Verticillium do not cause rot on the fine roots or crown. However, they always cause characteristic vascular discoloration in the taproot and crown of the plant. Distinguishing these two pathogens without a laboratory evaluation is not advised, but in general, Fusarium occurs earlier in the crop cycle and often causes a red-to-brown discoloration internally along the taproot and at the base of the crown. Symptoms of Verticillium on the above ground parts of head lettuce become obvious close to harvest; the taproot and crown tissue of infected plants have dark brown-to-black discolorations. Plants with INSV can also be infected with Sclerotinia (S. minor) which is recognized by the characteristic rotting of the crown tissue of the plant and the presence of white, cottony growth and small blacksclerotia (Photo 3). Plants infected with Sclerotinia easily break off at the soil line when you gently tug on them. However, if the plants do not break off at the soil line and do not show any rot on the crown tissue but do exhibit rot on the fine feeder roots or lower down on the taproot, then Pythium wilt is suspected and can be verified by laboratory evaluation.

    Sclerotinia infection on lettuce. Note that it infects and rots crown tissue of the plant.

    Biology and Symptoms of Pythium

    Pythium wilt is caused by the water mold, Pythium uncinulatum. It infects lettuce roots with swimming spores (zoospores) that move to the roots within the water film in the soil. Additionally, it produces a second type of spore (oospore) that allows the pathogen to survive in the soil in the absence of a host plant. Previous studies have reported P. uncinulatum is almost exclusively a pathogen of lettuce and does not cause disease on other vegetable crops. However, it remains unknown whether other crops may contribute to a build-up of the pathogen in the soil. Affected plants will exhibit rotting of the fine and tap roots (Photo 4) and frequently dark discoloration of the inner core of the main root (Photo 5). Symptoms of the above ground parts of the plant include stunting, yellowing, and wilting of the outer leaves and eventual death (Photo 6). Sometimes the plants have a characteristic look where the younger leaves remain upright, but the older leaves are totally wilted down to the soil (Photo 7). This year, we frequently observed fields where plants are infected with Pythium wilt but are also infected with INSV. These mixed infections are confusing and make it more difficult to distinguish what is the cause of the damage. In our experience to date, plants that show foliar symptoms of INSV and that have wilting older leaves are typically infected with both INSV and, in many cases, Pythium wilt. It should be mentioned that we have also observed plants infected with INSV as well as Fusarium.

    Pythium wilt infection of fine lettuce roots.
    Pythium wilt infection on lettuce taproot.
    Mini romaine infected with Pythium wilt.
    Romaine infected with INSV and Pythium wilt. Note that the older leaves are wilted and lay on the ground.

    The distribution of Pythium wilt in a lettuce field can be variable. Earlier in the summer, fields with this disease typically were infected along the upper or lower ends of the field indicating that the disease may be responding to irrigation or drainage issues. It is possible that there may be a difference in the level of infection between sprinkler and drip irrigated fields, but we cannot say anything definitive at this time. The disease has been found from King City to Castroville. There is a significant difference in the susceptibility of varieties. In fields with multiple leaf type lettuce, we have observed significant differences in susceptibility among varieties with red types being less susceptible (Photo 8). Recently, there have been severe losses in some fields. It is not clear as of this writing, but it is possible that the incidences occurred in response to the heat spells. It is likely that diseased plants were not able to withstand the weather stress due to damaged roots or that extra water applied to address the heat may have stimulated the development of Pythium wilt. Another observation we have made is that at times Pythium mostly infects the fine roots higher up on the root system and in other situations it is more severe at the bottom of the taproot (Photo 9) which may indicate disease initiated farther down on the root system. Given that the disease needs a period of soil saturation for the swimming spores to travel to the roots, issues with soil preparation, drainage and irrigation management may affect the severity of the disease.

    Difference in susceptibility of two green leaf lettuces and a green leaf and red leaf lettuce to Pythium.
    Plant with Pythium wilt infection lower down on the tap root (note the plant on the top with healthy fine roots higher up and infected tip of the tap root).

    Research Efforts

    Daniel Hasegawa is conducting research on the epidemiology and spread of thrips and INSV. JP Dundore Arias is working on a project with the California Leafy Greens Research Board monitoring the occurrence of Pythium wilt in the Salinas Valley. He is also characterizing isolates of this disease to better understand the organism and will be conducting preliminary evaluations of the sensitivity of the organism to fungicides. Given the rapid onset of severe damage of Pythium and the continued severity of INSV, we are trying to better understand these diseases and how they may interact. We are interested in receiving samples of Pythium wilt. Please contact Richard (rifsmith@ucdavis.edu) or JP (jdundorearias@csumb.edu) to submit samples.

    Authors: Richard Smith, JP Dundore Arias, Daniel Hasegawa and Steve Koike

    Farm Advisor, UCCE Monterey; Plant Pathology Professor, Cal State Monterey Bay; Research Entomologist, USDA ARS; Director, TriCal Diagnostics, respectively

  • Why Aren’t My Beans Drying Down?

    We cut our blackeye bean (cowpea) research plots at UC Davis almost 3 weeks ago and they’re still too green to harvest. If we tried now, the vines would get wrapped around the threshing cylinder.  Several growers in the Sacramento Valley have mentioned that their corn has sat at the same moisture level for weeks and is not drying down either, as one would normally expect for this time of year. But, nothing is normal this year!

    Why aren’t our crops drying down?

    Tragic fires throughout the West have pushed a lot of smoke and ash into the sky, creating fog-like conditions that reduce the intensity of the sun, shade crops, and lower temperatures. The blanket of smoke is like stepping into the shade under an awning on a 90oF day. This reduced sun intensity has affected the ability of crops to dry down in a timely manner. Increased humidity levels this past weeks haven’t helped either.

    While shading may be good for protecting tomatoes from sunburn with harvests running late due to COVID-related challenges, it is not good for drying down field crops.

    With the smoke finally dissipating, drying conditions are improving. We ended up turning our blackeye bean crop over to increase aeration and help it dry down.  Dry beans are sometimes turned to help dry the crop down, especially if they’re rained on, but the challenge is to be careful to prevent shattering.

    In corn, there aren’t any easy solutions.  One grower said their corn sat at 16.5% moisture for several weeks and finally they had to harvest it anyway. Dryers are available for drying corn and other crops to the proper storage moisture, but as we all know it’s expensive and with low grain prices this affects the bottom line.  — By Sarah Light & Rachael Freeman Long, UC Cooperative Extension

  • Study Finds 82 Percent of Avocado Oil Rancid or Mixed With Other Oils

    Consumer demand is rising for all things avocado, including oil made from the fruit. Avocado oil is a great source of vitamins, minerals and the type of fats associated with reducing the risk of heart disease, stroke and diabetes. But according to new research from food science experts at the University of California, Davis, the vast majority of avocado oil sold in the U.S. is of poor quality, mislabeled or adulterated with other oils.

    In the country’s first extensive study of commercial avocado oil quality and purity, UC Davis researchers report that at least 82 percent of test samples were either stale before expiration date or mixed with other oils. In three cases, bottles labeled as “pure” or “extra virgin” avocado oil contained near 100 percent soybean oil, an oil commonly used in processed foods that’s much less expensive to produce.

    “I was surprised some of the samples didn’t contain any avocado oil,” said Selina Wang, Cooperative Extension specialist in the Department of Food Science and Technology, who led the study recently published in the journal Food Control. “Most people who buy avocado oil are interested in the health benefits, as well as the mild, fresh flavor, and are willing to pay more for the product. But because there are no standards to determine if an avocado oil is of the quality and purity advertised, no one is regulating false or misleading labels. These findings highlight the urgent need for standards to protect consumers and establish a level playing field to support the continuing growth of the avocado oil industry.”

    Testing domestic and imported brands  

    Wang and Hilary Green, a Ph.D. candidate in Wang’s lab, analyzed various chemical parameters of 22 domestic and imported avocado oil samples, which included all the brands they could find in local stores and online. Wang and Green received a $25,000 grant from Dipasa USA, part of the Dipasa Group, a sesame-seed and avocado-oil processor and supplier based in Mexico.

    “In addition to testing commercial brands, we also bought avocados and extracted our own oil in the lab, so we would know, chemically, what pure avocado oil looks like,” Wang said.

    Test samples included oils of various prices, some labeled extra virgin or refined. Virgin oil is supposed to be extracted from fresh fruit using only mechanical means, and refined oil is processed with heat or chemicals to remove any flaws.

    Fifteen of the samples were oxidized before the expiration date. Oil loses its flavor and health benefits when it oxidizes, which happens over time and when exposed to too much light, heat or air. Six samples were mixed with large amounts of other oils, including sunflower, safflower and soybean oil.

    Only two brands produced samples that were pure and nonoxidized. Those were Chosen Foods and Marianne’s Avocado Oil, both refined avocado oils made in Mexico. Among the virgin grades, CalPure produced in California was pure and fresher than the other samples in the same grade.

    A push for standards

    Ensuring quality is important for consumers, retailers, producers and people throughout the avocado oil industry. Retailers want to sell quality products, shoppers want to get their money’s worth and honest producers want to keep fraudulent and low-quality oil out of the marketplace.

    But since avocado oil is relatively new on the scene, the Food and Drug Administration has not yet adopted “standards of identity,” which are basic food standards designed to protect consumers from being cheated by inferior products or confused by misleading labels. Over the last 80 years, the FDA has issued standards of identity for hundreds of products, like whiskey, chocolate, juices and mayonnaise. Without standards, the FDA has no means to regulate avocado oil quality and authenticity. 

    Avocado oil isn’t the only product without enforceable standards. Honey, spices and ground coffee are other common examples. Foods that fetch a higher price are especially ripe for manipulating, especially when adulterations can be too subtle to detect outside a lab.

    Wang is working to develop faster, better and cheaper chemical methods to detect adulteration so bulk buyers can test avocado oil before selling it. She is also evaluating more samples, performing shelf-life studies to see how time and storage affect quality, and encouraging FDA officials to establish reasonable standards for avocado oil.

    Wang has experience collaborating with industry and the FDA. Ten years ago, she analyzed the quality and purity of extra virgin olive oil and discovered that most of what was being sold in the U.S. was actually a much lower grade. Her research sparked a cascade of responses that led California to establish one of the world’s most stringent standards for different grades of olive oil. The FDA is working with importers and domestic producers to develop standards of identity for olive oil.

    “Consumers seeking the health benefits of avocado oil deserve to get what they think they are buying,” Wang said. “Working together with the industry, we can establish standards and make sure customers are getting high-quality, authentic avocado oil and the companies are competing on a level playing field.”

    Tips for consumers

    • The flavor of virgin avocado oil can differ by varieties and region. In general, authentic, fresh, virgin avocado oil tastes grassy, buttery and a little bit like mushrooms.
    • Virgin avocado oil should be green in color, whereas refined avocado oil is light yellow and almost clear due to pigments removed during refining.
    • Even good oil becomes rancid with time. It’s important to purchase a reasonable size that can be finished before the oil oxidizes. Store the oil away from light and heat. A cool, dark cabinet is a good choice, rather than next to the stove.  
    • How do you know if the oil is rancid? It starts to smell stale, sort of like play dough.
    • When possible, choose an oil that’s closest to the harvest/production time to ensure maximum freshness. The “best before date” is not always a reliable indicator of quality.

    – By Diane Nelson, UC Davis

  • COVID-19 Impacts on Food Supply Chain (May 12 Zoom Call)

    Why is milk being dumped and produce left to rot in fieldswhile grocery store shelves go empty during the COVID-19 pandemic? Why are grocery stores running out of meat, and eggs becoming so expensive?

    The head of California’s Department of Food and Agriculture, researchers from the University of California, Davis, and food purveyors will tackle these and other questions in an online panel discussion at 5 p.m. Tuesday, May 12.

    UC Davis invites the public to attend “Food Shortages in a Pandemic” over the web through Zoom conferencing. To do so, register online at least 48 hours in advance.

    The 90-minute event, which will include a question-and-answer period with the Zoom audience, will feature:

    • Karen Ross, secretary of the California Department of Food and Agriculture since 2011
    • Dan Sumner, director of the UC Agricultural Issues Center, professor of agricultural and resource economics at UC Davis, and former assistant secretary for economics at the U.S. Department of Agriculture
    • Bu Nygrens, co-owner and director of purchasing at Veritable Vegetable of San Francisco, which distributes organic produce from more than 200 small and mid-size growers to restaurants, markets and co-ops across five states
    • Chelsea Minor, corporate director of public affairs for Raley’s Supermarkets of West Sacramento, a regional grocery chain in Northern California and Nevada

    Moderating the event will be Catherine Brinkley, who, as an assistant professor in the Department of Human Ecology at UC Davis, studies the architecture of food supply networks. 

    The panel will discuss how the food supply chain works, why the COVID-19 pandemic has been so disruptive, how distributors and supply chains are adapting to serve restaurants and grocery stores, and whether changes can or should be made to make food systems more resilient.

    The lecture is the third in the Savor series, which explores some of the biggest food and beverage topics being studied today at UC Davis — a world leader in the study of agriculture. The series is presented by the Robert Mondavi Institute for Wine and Food Science and the UC Davis Library.

    – By Jessica Nusbaum and Julia Ann Easley, UC Davis

  • COVID-19 Impacts on Food Supply Chain (May 12 Zoom Call)

    Why is milk being dumped and produce left to rot in fields while grocery store shelves go empty during the COVID-19 pandemic? Why are grocery stores running out of meat, and eggs becoming so expensive?

    The head of California’s Department of Food and Agriculture, researchers from the University of California, Davis, and food purveyors will tackle these and other questions in an online panel discussion at 5 p.m. Tuesday, May 12.

    UC Davis invites the public to attend “Food Shortages in a Pandemic” over the web through Zoom conferencing. To do so, register online at least 48 hours in advance.

    The 90-minute event, which will include a question-and-answer period with the Zoom audience, will feature:

    • Karen Ross, secretary of the California Department of Food and Agriculture since 2011
    • Dan Sumner, director of the UC Agricultural Issues Center, professor of agricultural and resource economics at UC Davis, and former assistant secretary for economics at the U.S. Department of Agriculture
    • Bu Nygrens, co-owner and director of purchasing at Veritable Vegetable of San Francisco, which distributes organic produce from more than 200 small and mid-size growers to restaurants, markets and co-ops across five states
    • Chelsea Minor, corporate director of public affairs for Raley’s Supermarkets of West Sacramento, a regional grocery chain in Northern California and Nevada

    Moderating the event will be Catherine Brinkley, who, as an assistant professor in the Department of Human Ecology at UC Davis, studies the architecture of food supply networks. 

    The panel will discuss how the food supply chain works, why the COVID-19 pandemic has been so disruptive, how distributors and supply chains are adapting to serve restaurants and grocery stores, and whether changes can or should be made to make food systems more resilient.

    The lecture is the third in the Savor series, which explores some of the biggest food and beverage topics being studied today at UC Davis — a world leader in the study of agriculture. The series is presented by the Robert Mondavi Institute for Wine and Food Science and the UC Davis Library.

    – By Jessica Nusbaum and Julia Ann Easley, UC Davis

  • California Agricultural Employers, Workers Approach Smoke Concerns Differently

    In 2018, California wildfires burned more than 1.8 million acres and caused smoke to drift hundreds of miles. As the frequency and intensity of wildfires increases with climate change, California agricultural workers are at greater risk of smoke exposure as they often have no option but to work outdoors.

    A new study from researchers at the University of California, Davis, finds that while wildfires and smoke exposure are recognized by farmworkers and employers as a growing threat and safety concern, the means to address these concerns differs between the two groups.

    “What stood out in this study is the substantial disparities between agricultural employers and farmworkers,” said Heather Riden with the Western Center for Agricultural Health and Safety at UC Davis.

    Riden, who led the research in partnership with the California Institute for Rural Studies, said that while growers and employers expressed concern about poor air quality at the time of the study in 2018, many had no clear plans or protocols for measuring air quality or managing workers in such conditions. While the public is advised to stay indoors due to poor air quality during a wildfire, agricultural work often continues.

    The study also found that when farmworkers were offered protective masks, many found them difficult to use while working due to heat-related discomfort and chafing. Others believed wearing two bandanas over mouth and nose would provide just as much protection.

    Farmworkers’ experience is compounded by economic need.

    “Many farmworkers will continue working, even in unsafe conditions, to support their families. They don’t have many other options,” said Riden.

    New regulations

    Last year, the state Division of Occupational Safety and Health, better known as Cal/OSHA, enacted an emergency regulation requiring employers to take measures to protect workers from wildfire smoke when the Air Quality Index reaches 151 or greater, which is considered unhealthy. Riden said as CAL/OSHA begins to craft permanent regulations, she hopes it takes the study’s findings into consideration.  

    “This highlights the need for better awareness for both agricultural employers and farmworkers about the health risks associated with wildfire smoke,” said Riden. “Employers also need training materials and concrete steps they can take to protect workers.”

    To assist agricultural employers with meeting the requirements outlined in the newly adopted regulation, the Western Center for Agricultural Health and Safety developed training materials and an employer checklist.

    The study was based on interviews and focus groups with California agricultural employers and workers in the Salinas, San Joaquin and Imperial valleys. Support for the study came from the Centers for Disease Control and Prevention, and the National Institute for Occupational Safety and Health –By Amy Quinton, UC Davis