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California Agriculture, Vol. 51, No.2

Water and food safety: What's the basis for sound policy?
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.
March-April 1997
Volume 51, Number 2

Peer-reviewed research and review articles

Research and reason can minimize foodborne and waterborne illnesses
by Dean O. Cliver, Edward R. Atwill
| Full text HTML  | PDF  
More research is needed to help government, food producers and consumers reduce outbreaks of foodborne and waterborne illness.
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.
Sidebar: Giardia also threatens drinking water supplies
by Tim Stephens
Full text HTML  | PDF  
Four weed management systems compared: Mulch plus herbicides effectively control vineyard weeds
by Clyde L. Elmore, John Roncoroni, Layne Wade, Paul Verdegaal
| Full text HTML  | PDF  
Chopping the cover crop biomass and spreading the mulch in the vine row was very effective the second year, when more biomass was produced and weeds were controlled in the vine row before the mulch was applied.
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.
Sheep grazing effectively controls weeds in seedling alfalfa
by Carl E. Bell, Juan N. Guerrero
| Full text HTML  | PDF  
A 3-year experiment showed that sheep can provide weed control comparable to that of herbicides in seedling alfalfa.
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.
New whitefly-transmitted closterovirus identified in tomatoes
by Gail C. Wisler, James E. Duffus, Hsing-Yeh Liu, Ruhui Li, Bryce W. Falk
| Full text HTML  | PDF  
A new virus transmitted by the green-house whitefly has been identified in both field- and greenhouse-grown tomatoes in California, North Carolina and Italy.
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.
Intensive land preparation emits respirable dust
by Heike Clausnitzer, Michael J. Singer
| Full text HTML  | PDF  
Land preparation, such as land planing, ripping, plowing and disking, produced significantly higher concentrations of respirable dust than most other cultivation activities.
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.
Packing-line modifications reduce pitting and bruising of sweet cherries
by Joseph A. Grant, James F. Thompson
| Full text HTML  | PDF  
Cluster cutting and hydrocooling caused the greatest damage to sweet cherries during the packing process, but damage was reduced when these operations were modified.
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.
Ice creams and frozen yogurts vary widely in key nutrients
by Christine M. Bruhn, John C. Bruhn
| Full text HTML  | PDF  
Ice creams varied from 70 to 270 calories and from 0 to 18 grams of fat per half-cup serving.
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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California Agriculture, Vol. 51, No.2

Water and food safety: What's the basis for sound policy?
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.
March-April 1997
Volume 51, Number 2

Peer-reviewed research and review articles

Research and reason can minimize foodborne and waterborne illnesses
by Dean O. Cliver, Edward R. Atwill
| Full text HTML  | PDF  
More research is needed to help government, food producers and consumers reduce outbreaks of foodborne and waterborne illness.
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.
Sidebar: Giardia also threatens drinking water supplies
by Tim Stephens
Full text HTML  | PDF  
Four weed management systems compared: Mulch plus herbicides effectively control vineyard weeds
by Clyde L. Elmore, John Roncoroni, Layne Wade, Paul Verdegaal
| Full text HTML  | PDF  
Chopping the cover crop biomass and spreading the mulch in the vine row was very effective the second year, when more biomass was produced and weeds were controlled in the vine row before the mulch was applied.
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.
Sheep grazing effectively controls weeds in seedling alfalfa
by Carl E. Bell, Juan N. Guerrero
| Full text HTML  | PDF  
A 3-year experiment showed that sheep can provide weed control comparable to that of herbicides in seedling alfalfa.
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.
New whitefly-transmitted closterovirus identified in tomatoes
by Gail C. Wisler, James E. Duffus, Hsing-Yeh Liu, Ruhui Li, Bryce W. Falk
| Full text HTML  | PDF  
A new virus transmitted by the green-house whitefly has been identified in both field- and greenhouse-grown tomatoes in California, North Carolina and Italy.
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.
Intensive land preparation emits respirable dust
by Heike Clausnitzer, Michael J. Singer
| Full text HTML  | PDF  
Land preparation, such as land planing, ripping, plowing and disking, produced significantly higher concentrations of respirable dust than most other cultivation activities.
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.
Packing-line modifications reduce pitting and bruising of sweet cherries
by Joseph A. Grant, James F. Thompson
| Full text HTML  | PDF  
Cluster cutting and hydrocooling caused the greatest damage to sweet cherries during the packing process, but damage was reduced when these operations were modified.
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.
Ice creams and frozen yogurts vary widely in key nutrients
by Christine M. Bruhn, John C. Bruhn
| Full text HTML  | PDF  
Ice creams varied from 70 to 270 calories and from 0 to 18 grams of fat per half-cup serving.
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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