California Agriculture
California Agriculture
California Agriculture
University of California
California Agriculture

Current issue and featured articles

April-June 2021
Volume 75, Number 2

Peer-reviewed research and review articles

Robotic strawberry harvest is promising but will need improved technology and higher wages to be economically viable
by Timothy Delbridge
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An analysis of harvest efficiencies and wage rates suggests that adoption of robotic harvesters is not yet economically feasible for large strawberry growers.
While the prospect of robotic harvest in strawberry production has received much attention within the strawberry industry and the popular press, there is little available information on the economic feasibility of this technology. It is not clear how close the industry is to being able to profitably adopt robotic harvest systems; also unclear is the relative importance of wage rates, robotic harvest efficiencies and machinery field speeds on the adoption threshold. This study aims to clarify these issues by estimating the net income to strawberry production under robotic harvest scenarios, and comparing the values to standard enterprise budgets for strawberry production in California under different wage rates for harvest labor. Results confirm that robotic harvest remains economically unviable under current wage rates and the field speeds and harvest efficiencies achieved by leading robotic harvest development teams. However, results indicate that with expected increases in wage rates in the coming years, and with modest improvements in the technical parameters, use of robotic systems will likely become profitable in some form.
The potential threat of branched broomrape for California processing tomato: A review
by O. Adewale Osipitan, Bradley D. Hanson, Yaakov Goldwasser, Matthew Fatino, Mohsen B. Mesgaran
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After a 40-year absence, branched broomrape has reappeared in commercial California tomato fields, raising concern and prompting the search for integrated approaches to management.
Branched broomrape (Phelipanche ramosa), a parasitic weed that was the focus of a $1.5 million eradication effort four decades ago in California, has recently re-emerged in tomato fields in several Central Valley counties. Processing tomatoes are important to the California agricultural economy; the state produced over 90% of the 12 million tons of tomatoes grown in the United States in 2018. Branched broomrape is listed as an “A” noxious weed by the California Department of Food and Agriculture (CDFA); discovery of broomrape in California tomato fields leads to quarantine and crop destruction without harvest, resulting in significant economic loss to growers. In countries where broomrape is common, yield reductions caused by this parasitic weed can range from moderate to 80%, depending upon the infestation level, host and environmental conditions. Developing a detailed understanding of the biology of this weed under local conditions is an important step towards developing effective management plans for California. In this review, we discuss branched broomrape in the context of California production systems, particularly of tomato. We also discuss the potential management practices that could help to prevent or reduce the impacts of branched broomrape in tomatoes and other host crops.
Point- and reach-scale measurements are important for determining accurate seepage rates in controlled flow channels
by Mark E. Grismer
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Point- and reach-scale field measurements are evaluated as a means to measure seepage rates in controlled flow channels at two locations in California's Central Valley.
A critical component of water-resources management in the irrigated agriculture landscape, particularly those landscapes dependent on groundwater availability, is determining groundwater recharge rates from streams and other channels. In California, flows in many such channels are “controlled” by upstream reservoir releases to meet downstream urban, irrigation and environmental water requirements. Seepage volumes from these channels and how they might vary during controlled release periods is a key component of meeting downstream riparian and groundwater-pumping needs. Understanding annual seepage from streamflow channels is also important in developing water budgets as part of the management of groundwater resources under the Sustainable Groundwater Management Act (SGMA) in California. However, direct measurements of channel seepage rates are infrequent or unavailable, and these rates, or associated volumes, are most often only estimated. Here we describe direct point- and reach-scale field measurements of channel seepage rates in Lower Putah Creek (Solano County) and in distribution lateral channels of the Oakdale Irrigation District on the east side of the San Joaquin Valley (San Joaquin and Stanislaus counties). We measured overall average seepage rates of about 2 feet (610 mm) per day at both locations and determined how these rates varied spatially and temporally during the summer when channel flows are controlled for downstream requirements.
Integration of grazing and herbicide application improves management of barb goatgrass and medusahead in pasture and rangelands
by Travis M. Bean, Josh S. Davy, Guy B. Kyser, Elise S. Gornish
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The combination of high-intensity, short-duration grazing with precisely timed applications of glyphosate improves management of invasive annual grasses.
The invasive annual grasses barb goatgrass (Aegilops triuncialis L.) and medusahead (Elymus caput-medusae L.) are widespread in western states and present management challenges on grasslands. To develop an integrated management strategy for these species, we treated sites in five pastures in Mendocino County, comparing combinations of intensive sheep grazing, glyphosate herbicide (low and high), and application timings (tillering, boot and heading stage). We found that grazing alone reduced barb goatgrass spikelet densities by 68% and the number of seeds per spikelet by 35%. Both rates of glyphosate application without grazing had similar effects on seed production. High and low glyphosate application at tillering resulted in almost complete control of both target species. Boot- and heading-stage applications reduced barb goatgrass density by 39% and 32%, respectively. Application at the boot stage also resulted in an 82% reduction in number of seeds per barb goatgrass spikelet. Our results suggest that intensive grazing may be a useful management strategy to reduce barb goatgrass and medusahead spikelet densities and barb goatgrass seed numbers, especially when integrated with a boot- or heading-stage glyphosate application.
Growers follow the label: An analysis of bee-toxic pesticide use in almond orchards during bloom
by Jennie L. Durant, Brittney K. Goodrich, Kelly T. Chang, Evan Yoshimoto
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Pesticide use data indicate that almond growers have reduced labeled bee-toxic pesticide use, but unlabeled bee-toxic agrochemicals are still applied during bloom.
California almond orchards are most U.S. beekeepers' first stop on their pollination and honey production circuit, so the agrochemicals bees are exposed to in almonds can shape the vitality of their colony for the rest of the year. We explored the potential for honey bee exposure to bee-toxic agrochemicals during almond bloom by utilizing the California Department of Pesticide Regulations' Pesticide Use Report database from 1990 to 2016. We found that overall, growers are observing the pesticide labels and reducing their use of labeled bee-toxic pesticides during almond bloom. However, we also found that insect growth regulators, fungicides and organosilicone surfactants — agrochemicals often not labeled as toxic to bees — are commonly applied during almond bloom. These agrochemicals can be sublethally or synergistically toxic to adult honey bees and bee larvae, presenting potential harm to colonies during almond pollination. Our findings demonstrate the need for a shift in the U.S. Environmental Protection Agency's labeling requirements, as well as continued communication between almond growers, pesticide applicators and beekeepers to keep colonies at a low risk of bee-toxic agrochemical exposure.

News and opinion

The first SGMA groundwater market is trading: The importance of good design and the risks of getting it wrong
by Sarah Heard, Matthew Fienup, E. J. Remson
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Groundwater markets are a promising tool for basins implementing SGMA, but they are complex, and good design is essential.

Early view articles

Low prevalence of handwashing and importance of signage at California county fair animal exhibits
by Melissa T. Ibarra, Cheryl L. Meehan, Miles Daniels, Woutrina A. Smith, Martin H. Smith
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Signage showing a link between animal contact and pathogen transmission may lead to increased frequency of handwashing at California County fairs.
Disease outbreaks among visitors at venues where animals are exhibited, such as animal shows at county fairs or petting zoos, are national public health concerns. Zoonotic disease transmission at fairs can occur through a variety of pathways, including direct contact with livestock and indirect exposure through contact with animals' immediate surroundings. Handwashing can reduce pathogen transmission. The goal of this observational study was to determine rates of handwashing among county fair visitors and to learn whether signage and/or contact with animals were correlated with handwashing practice. The investigation was conducted at four county fairs located across two geographic regions of California. Observations occurred over the course of one summer. Results from our observations of fair visitors revealed a low overall prevalence (5%) of handwashing behavior. However, fair visitors who made contact with animals were more likely to wash their hands. Additionally, those individuals who walked through barns where handwashing signage was present were significantly more likely to wash their hands than those who visited barns without signage.
Addressing organizational climate can potentially reduce sexual harassment of female agricultural workers in California
by Malcolm Hobbs, Emanuelle Klachky, Monica Cooper
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Assessing antecedents for sexual harassment among California's agricultural workers yields insight into the causes and consequences of this behavior and suggests ways to mitigate it.
Workplace sexual harassment (SH) has been highlighted as a key issue for female agricultural workers in the United States. This study investigated how workers' descriptive data (age, job experience, attitudes) and specific organizational variables (how work crews are structured) potentially facilitate SH in an agricultural setting. Harassment was reported by 30% of surveyed female viticulture workers in their current jobs. Harassed women tended to be younger, employed seasonally and working in crews where hostile sexist views were prevalent. Harassment affected worker productivity; harassed women and their male co-workers were less satisfied with their jobs and more likely to seek other employment. Efforts to address SH by restructuring at the level of the field crew may be ineffective. Instead, addressing workers' hostile sexist attitudes and the extent to which an organization tolerates SH appears to have the most promise for reducing SH in agricultural industries.


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