March-April 1997

Cover: Dayna Wilson, Cooperative Extension dairy program representative for Sonoma and Marin counties, tests water quality in Stemple Creek, part of the watershed that empties into Tomales Bay.

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California Agriculture, March-April 1997

Volume 51, Number 2
Water and food safety: What's the basis for sound policy?

peer-reviewed research articles

Research and reason can minimize foodborne and waterborne illnesses
by Dean O. Cliver , Edward R. Atwill
pp8-14, doi#10.3733/ca.v051n02p8
Abstract
Several outbreaks of foodborne and waterborne illness have directed the nation's attention to intestinal pathogens that are threats to public health. Among these pathogens are Cryptosporidium parvum and Escherichia coli O157:H7, which are known to infect and to be spread by not only humans, but also livestock and various species of wildlife. New regulations aimed at controlling these pathogens are being implemented, despite a shortage of scientific information about their ecology, how they contaminate food and water supplies, and how to detect and eliminate such contamination. Research is needed to address these issues and to develop better technologies for pathogen detection, water treatment and food processing.
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Four weed management systems compared: Mulch plus herbicides effectively control vineyard weeds
by Clyde L. Elmore , John Roncoroni , Layne Wade , Paul Verdegaal
pp14-18, doi#10.3733/ca.v051n02p14
Abstract
Mulches have been used for many years to control weeds by smothering the weed seedlings. A 2-year study in a Lodi grape vineyard compared the weed-control effectiveness of herbicides, cultivation, cover crop biomass and wood-chip mulch and the cost of these practices. The most effective and least expensive treatment over the 2 years was the use of preemergence herbicides and a post-emergence herbicide as needed. Growing cover crops, chopping the biomass and placing it into the vine row was very effective the second year, when more biomass was produced and weeds were controlled prior to mulch placement. The mulch was persistent in the field and should give long-term weed-control benefits, which were not evaluated in this study.
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Sheep grazing effectively controls weeds in seedling alfalfa
by Carl E. Bell , Juan N. Guerrero
pp19-23, doi#10.3733/ca.v051n02p19
Abstract
A 3-year experiment compared sheep grazing to herbicides for weed control in seedling alfalfa in the Imperial Valley. Yields for the first season were highest with the grazed treatment and the untreated control because of the contribution of weeds to the hay. There was no difference in the alfalfa forage yield and density among any of the treatments. Lambs preferred weeds to the alfalfa, and the nutritional value of the weeds was usually comparable to that of the alfalfa.
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New whitefly-transmitted closterovirus identified in tomatoes
by Gail C. Wisler , James E. Duffus , Hsing-Yeh Liu , Ruhui Li , Bryce W. Falk
pp24-26, doi#10.3733/ca.v051n02p24
Abstract
A new virus of tomato, tomato infectious chlorosis virus (TICV), has been identified in both field-and greenhouse-grown tomatoes in California, North Carolina and Italy. TICV is transmitted by the greenhouse whitefly (Trialeurodes vaporariorum) in a semipersistent manner. TICV infects a wide range of plant hosts, and has been found naturally infecting Petunia and Ranunculus in greenhouses, and tree tobacco, commercial artichoke and bristly oxtongue in the southern coastal region of California. Because of its wide host range, the prevalence of the greenhouse whitefly in fields and greenhouses, and the movement of susceptible plant hosts within and among countries around the world, TICV is a potential problem for the world's tomato industry. TICV caused an estimated $2 million loss in Orange County in 1993. Control measures include whitefly control, confirmation of TICV infection by a diagnostic test and roguing of infected plants.
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Intensive land preparation emits respirable dust
by Heike Clausnitzer , Michael J. Singer
pp27-30, doi#10.3733/ca.v051n02p27
Abstract
Respirable dust (RD), defined as particles smaller than 4 ?m diameter, was collected at the implement from 29 farming operations performed for furrow-irrigated tomato, corn, and wheat crop production over a 2-year period. Land preparation, such as land planing, ripping, plowing, and disking, produced significantly higher concentrations of RD than most other cultivation operations. Land preparation accounted for 67% of all farming operations, but produced 82% of the RD. The number of operations and the timing of land preparation were responsible for the difference in RD concentrations among the seven 2-year crop rotations. Of the studied crops, tomato and corn were the most intensively cultivated and yielded the highest RD amounts. Soil moisture was an important environmental variable that influenced the amount of dust and the variability in dust concentration from sample to sample. Among the cropping systems studied, those that required more tillage or land preparation to be performed when the soil was driest produced the most RD.
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Packing-line modifications reduce pitting and bruising of sweet cherries
by Joseph A. Grant , James F. Thompson
pp31-35, doi#10.3733/ca.v051n02p31
Abstract
Packing-house operations that cause sweet cherry fruit pitting or bruising damage were evaluated in a 4-year field study. Packing lines varied considerably in amounts of damage imparted to fruit, as did individual packinghouse operations. Damage was reduced by slowing fruit speed in cluster cutters, by operating cluster cutters at high throughput rates and by reducing water-drop height in shower hydrocoolers.
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Ice creams and frozen yogurts vary widely in key nutrients
by Christine M. Bruhn , John C. Bruhn
pp36-40, doi#10.3733/ca.v051n02p36
Abstract
The combined forces of consumer demand, nutritional labeling requirements and product innovation have led to a range of frozen dairy desserts that vary significantly in several nutrients highlighted on the nutritional label. Ice creams and yogurts available in California were surveyed in 1995 for nutrient content. Ice creams varied from 70 to 270 calories and from 0 to 18 grams of fat per half-cup serving. Two ice cream products met the Food and Drug Administration's definition for a “good source” of vitamin A, providing 10% or more of the Recommended Daily Value of the nutrient, and 21 were “good sources” of calcium. While no frozen yogurts met the requirement for a good source of vitamin A, 10 were good sources of calcium.
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editorial, news, letters & science briefs

EDITORIAL: Scientists work with industry to safeguard food and water
by W.R. Gomes
pp2, doi#10.3733/ca.v051n02p2
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Ranchers manage land to enhance watershed
Editors
pp4-5, doi#10.3733/ca.v051n02p4
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UC scientists seek to ensure safe meat
Editors
pp5-6, doi#10.3733/ca.v051n02p5
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San Francisco water district targets cattle
by Tim Stephens
pp7, doi#10.3733/ca.v051n02p7
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Sidebar: Giardia also threatens drinking water supplies
by Tim Stephens
pp10, doi#10.3733/ca.v051n02p10
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