California Agriculture
California Agriculture
California Agriculture
University of California
California Agriculture

Current issue and featured articles

January-March 2017
Volume 71, Number 1

Peer-reviewed research and review articles

The palm weevil Rhynchophorus vulneratus is eradicated from Laguna Beach
by Mark S. Hoddle, Christina D. Hoddle, Mohammed Alzubaidy, John Kabashima, J. Nicholas Nisson, Jocelyn Millar, Monica Dimson
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A rapid, coordinated response to the discovery of an invasive pest attacking Canary Island date palms in California succeeded in eradicating it.
In October 2010, Rhynchophorus vulneratus, originally identified as the red palm weevil, R. ferrugineus, was discovered infesting Canary Island date palms in Laguna Beach, California. The red palm weevil has caused extensive mortality of palms in the Mediterranean, the Middle East and North Africa, and its discovery in California caused concern for the state's ornamental palm and date industries and the many palms in Southern California landscapes. A rapid, coordinated effort led to the deployment of traps baited with the weevil's aggregation pheromone, coordinated pesticide applications to privately owned palms and destruction of palms at advanced stages of infestation. Research confirmed the chemical components of the aggregation pheromone, assessed the efficacy of trapping strategies and resolved the taxonomic identity, native range and putative region of origin for the population detected in Laguna Beach. The last confirmed detection of a live R. vulneratus was Jan. 20, 2012. USDA-APHIS declared this weevil eradicated from California on Jan. 20, 2015. The estimated cost of the eradication was $1,003,646.
How many workers are employed in California agriculture?
by Philip Martin, Brandon Hooker, Muhammad Akhtar, Marc Stockton
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An analysis of data from agricultural employers suggests that California has a stable agricultural workforce.
In 2014, the average employment of hired workers in California crop and livestock agriculture, counting all occupations, rose by 10% to 410,900. However, although the state reports the number of jobs on farms regularly, it does not report the number of workers who fill these jobs. We analyzed all Social Security numbers reported by farm employers in 2014 and found two workers for each average or year-round equivalent farm job, making the total number of farmworkers employed in agriculture 829,300, or twice average employment. Approximately 83% of farmworkers had their maximum earnings with an agricultural employer in 2014, and almost 80% of those primary farmworkers were employed by crop support firms (392,000) or fruit and nut farms (154,000). Over 60% of all workers had only one farm employer, followed by 27% with two or more farm employers, and 35% were employed in Kern (116,000), Fresno (96,000) and Monterey (82,000) counties. These data show that California has a remarkably stable farm workforce: most farmworkers are attached to one farm employer, often a labor contractor who moves them from farm to farm.
Irrigation method does not affect wild bee pollinators of hybrid sunflower
by Hillary Sardiñas, Collette Yee, Claire Kremen
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The number of bees nesting and foraging in drip- versus furrow-irrigated fields were similar, suggesting growers can switch to drip without reducing pollination.
Irrigation method has the potential to directly or indirectly influence populations of wild bee crop pollinators nesting and foraging in irrigated crop fields. The majority of wild bee species nest in the ground, and their nests may be susceptible to flooding. In addition, their pollination of crops can be influenced by nectar quality and quantity, which are related to water availability. To determine whether different irrigation methods affect crop pollinators, we compared the number of ground-nesting bees nesting and foraging in drip- and furrow-irrigated hybrid sunflower fields in the Sacramento Valley. We found that irrigation method did not impact wild bee nesting rates or foraging bee abundance or bee species richness. These findings suggest that changing from furrow irrigation to drip irrigation to conserve water likely will not alter hybrid sunflower crop pollination.
Wood chip denitrification bioreactors can reduce nitrate in tile drainage
by Tim Hartz, Richard Smith, Mike Cahn, Thomas Bottoms, Sebastian Castro Bustamante, Laura Tourte, Kenneth Johnson, Luke Coletti
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A bioreactor study at Salinas vegetable farms reduces nitrate-nitrogen in drainage to regulatory levels.
Widespread contamination of surface water with nitrate-nitrogen (NO3-N) has led to increasing regulatory pressure to minimize NO3-N release from agricultural operations. We evaluated the use of wood chip denitrification bioreactors to remove NO3-N from tile drain effluent on two vegetable farms in Monterey County. Across several years of operation, denitrification in the bioreactors reduced NO3-N concentration by an average of 8 to 10 milligrams per liter (mg L-1) per day during the summer and approximately 5 mg L-1 per day in winter. However, due to the high NO3-N concentration in the tile drainage (60 to 190 mg L-1), water discharged from the bioreactors still contained NO3-N far above the regulatory target of < 10 mg L-1. Carbon enrichment (applying soluble carbon to stimulate denitrifying bacteria) using methanol as the carbon source substantially increased denitrification, both in laboratory experiments and in the on-farm bioreactors. Using a carbon enrichment system in which methanol was proportionally injected based on tile drainage NO3-N concentration allowed nearly complete NO3-N removal with minimal adverse environmental effects.

Editorial, News, Letters and Science Briefs

Drones in California research and extension
by Maggi Kelly
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Unmanned aerial systems for agriculture and natural resources
by Sean D. Hogan, Maggi Kelly, Brandon Stark, YangQuan Chen
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Trump and U.S. immigration policy
by Philip Martin
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Lindcove REC: Developing citrus varieties resistant to huanglongbing disease
by Hazel White
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Mark Hoddle: Smiting weevils
by Jim Downing
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Research to policy: Enabling oak woodland restoration
by Debbie Thompson
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Early view articles

Soil nitrate testing supports nitrogen management in irrigated annual crops
by Patricia A. Lazicki, Daniel Geisseler
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Soil NO3 testing can help growers use N fertilizers efficiently.
Soil nitrate (NO3) tests are an integral part of nutrient management in annual crops. They help growers make field-specific nitrogen (N) fertilization decisions, use N more efficiently and, if necessary, comply with California's Irrigated Lands Regulatory Program, which requires an N management plan and an estimate of soil NO3 from most growers. As NO3 is easily leached into deeper soil layers and groundwater by rain and excess irrigation water, precipitation and irrigation schedules need to be taken into account when sampling soil and interpreting test results. We reviewed current knowledge on best practices for taking and using soil NO3 tests in California irrigated annual crops, including how sampling for soil NO3 differs from sampling for other nutrients, how tests performed at different times of the year are interpreted and some of the special challenges associated with NO3 testing in organic systems.
Yield in almond is related more to the abundance of flowers than the relative number of flowers that set fruit
by Sergio Tombesi, Bruce D. Lampinen, Samuel Metcalf, Theodore M. DeJong
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Maximizing healthy populations of productive spurs is key to optimizing yields in commercial almond orchards.
Almond tree yield is a function of the number of flowers on a tree and the percentage of flowers that set fruit. Almonds are borne on spurs (short proleptic shoots that can have both leaves and flowers). Almond tree spur dynamics research has documented that previous year spur leaf area is a predictive parameter for year-to-year spur survival, spur flowering and to a lesser extent spur fruiting, while previous year fruit bearing has a negative impact on subsequent year flowering. However, a question remained about whether yields are more dependent on flower numbers or relative fruit set of the flowers that are present. The aim of the present work was to compare the importance of flower abundance with that of relative fruit set in determining the productivity of a population of tagged spurs in almond trees over a 6-year period. Overall tree yield among years was more sensitive to total number of flowers on a tree rather than relative fruit set. These results emphasize the importance of maintaining large populations of healthy flowering spurs for sustained high production in almond orchards.
Lessons learned: How summer camps reduce risk factors of childhood obesity
by Gretchen L. George, Lucia L. Kaiser, Constance Schneider
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Results suggest that youth in summer nutrition and fitness camps may lose more weight than those in non-nutrition-themed camps.
The purpose of this article is to present findings related to parent- and youth-reported outcomes from a nutrition- and fitness-themed summer camp targeting low-income families and to identify lessons learned in the implementation, evaluation and sustainability of a summer program. The Healthy Lifestyle Fitness Camp, offered through UC Cooperative Extension (UCCE), was a summer camp program for low-income youth at high risk for obesity. From 2009 to 2012, UCCE nutrition staff in Fresno County collaborated with the camp staff to provide a 6-week nutrition education program to the campers and their parents. Anthropometry and dietary data were collected from youth. Data about food preferences and availability were collected from youth and parents. As reported by parents in pre- to immediately post-camp surveys, Healthy Lifestyle Fitness campers consumed fruits and vegetables promoted at camp more often, relative to a comparison group of youth in a nearby non-nutrition themed camp. Summer programs may be an effective tool in the reduction of childhood obesity risk factors if implemented appropriately into the community and through the utilization of supportive partnerships such as UCCE and local parks and recreation departments.
Editor Jim Downing talks about what's in the current issue of California Agriculture journal — drones, Trump and immigration, citrus research, a threat to California's palm trees, and more.


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