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California Agriculture, Vol. 49, No.5

Oak rescue efforts: What have we learned?
Cover:  UC natural resources specialist Doug McCreary inspects plastic tree tubes shielding small oaks, willows and cottonwoods from rodents and grazing cattle. The goal is to restore more natural vegetation to this river bed at the Sierra Foothill Research and Extension Center. Photo by Jack Kelly Clark
September-October 1995
Volume 49, Number 5

Peer-reviewed research and review articles

Long-term survival question: Why do oaks produce boom-and-bust seed crops?
by Walter D. Koenig, Jean Knops
| Full text HTML  | PDF  
Acorn production of California oaks correlates with weather conditions favorable for pollination and, in two species, rainfall 1 and 2 years prior o acorn fall.
Annual differences in acorn crop size of California oaks do not correlate with rainfall the year before, but instead with weather conditions favorable for pollination and, in two species, rainfall 1 and 2 years prior to acorn fall. Despite considerable differences in mean productivity, correlated in part with local differences in water and nutrient availability, acorn production by individual trees within populations are generally synchronous. Synchrony extends over fairly large geographic areas, although whether on a statewide scale is not yet known. Knowledge of acorn production patterns may facilitate conservation of oaks rangelands, improve our understanding of wildlife ecology and provide insights into the social structure of California's Native Americans.
Planted blue oaks may need help to survive in Southern Sierras
by Theodore E. Adams, Neil K. McDougald
| Full text HTML  | PDF  
Careful side selection, control of weed competition and protection from rodents may be needed to restock blue oaks on California rangelands.
Competition from annual herbaceous plants is one of many factors inhibiting establishment of blue oaks in California. Other factors include drought and large and small mammal depredation; gophers are a particularly serious threat to the seedling's emergence and survival. To measure the impact of these and other factors, a series of studies compared the emergence and survival of directly seeded acorns and 2-month-old nursery stock. Results show that careful site selection, control of competition, and protection from mammal predators may all be needed to promote success of restocking programs on California rangelands.
Blue oak acorns more viable in Madera County than Kern County
by Ralph L. Phillips, Neil K. McDougald, Douglas McCreary
| Full text HTML  | PDF  
Acorns from Madera County were larger and more of their seedlings emerged from the soil and at a faster rate.
Acorns from native blue oaks growing in Madera and Kern counties were evaluated for quality in this 2-year study. Acorns from Madera County were larger and more of their seedlings emerged from the soil and at a faster rate than acorns from Kern County. Insect infestation and disease in the acorns were not consistent during the study.
Optimizing tomato distribution to processors lifts profits little
by Catherine A. Durham, Richard J. Sexton, Joo Ho Song
| Full text HTML  | PDF  
Interregional transport of tomatoes for processing is excessive, but a study suggests that optimizing allocation would improve industry profit only 1.9%.
Tomatoes are often hauled long distances in Northern and Central California. Because production areas and processing facilities are not geographically well aligned, processors compete across relatively long distances to procure tomatoes. In this study of the field-to-processor distribution of processing tomatoes, a nonlinear programming model was developed to determine the optimal distribution of tomatoes from the 13 highest-producing counties to the 32 processing plants in the region. Results suggest that excessive interregional haulage of tomatoes occurs, but the additional industry profit from implementing the optimal allocation versus the estimated actual allocation was only 1.9%.
Consistent annual treatment helps future olive leaf spot control
by Beth L. Teviotdale, G. Steven Sibbett
| Full text HTML  | PDF  
One annual fungicide treatment should control olive leaf spot in most orchards, but a second spray may help where conditions favor disease development.
Tulare County research revealed that an orchard's disease history influences how well annual copper fungicide treatments will work in controlling olive leaf spot. Elevated disease levels are not easily reduced in 1 year, and consistent annual treatment is important for future disease control as well as for protection in the current year.
Leaf removal improves fungicide control of powdery mildew in SJV grapes
by James J. Stapleton, George M. Leavitt, Paul S. Verdegaal
| Full text HTML  | PDF  
On-farm experiments showed that leaf removal reduced powdery mildew and facilitated improved spray coverage in fruiting zones.
Basal leaf removal, which has been used to reduce damage from bunch rots and seasonal leafhopper infestations, was tested for its effects on powdery mildew in the San Joaquin Valley. Powdery mildew is one of the most damaging diseases of wine grapes in California. On-farm experiments showed that leaf removal reduced the disease in two of five experiments and facilitated improved spray coverage in grapevine fruiting zones. Leaf removal can improve the effectiveness of fungicide programs in reducing powdery mildew damage, but should not be relied upon alone to control the disease.
Farm labor contractors play new roles in agriculture
by Dawn Thilmany, Philip L. Martin
| Full text HTML  | PDF  
Growers say they find it easier and more cost-effective to use FLCs to recruit and supervise workers.
The role of farm labor contractors in California agriculture has evolved along with changes in the state's immigration and labor policies. Today, the role of FLCs in California is expanding, due in part to an increase in farm labor regulations. Growers say they find it easier and more cost-effective to use FLCs for the recruitment and supervision of agricultural workers. Yet the issue of who is liable for labor law violations and to what extent remains in dispute. This study investigates the changing relationship between FLCs and their grower-clients.

Editorial, News, Letters and Science Briefs

Competitive grants: Wave of the future?
by Henry J. Vaux
Full text HTML  | PDF  
Science Briefs
by Editors
Full text HTML  | PDF  
Urbanization crowds out oaks
by Editors
Full text HTML  | PDF  
Letters
From our readers
Full text HTML  | PDF  
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California Agriculture, Vol. 49, No.5

Oak rescue efforts: What have we learned?
Cover:  UC natural resources specialist Doug McCreary inspects plastic tree tubes shielding small oaks, willows and cottonwoods from rodents and grazing cattle. The goal is to restore more natural vegetation to this river bed at the Sierra Foothill Research and Extension Center. Photo by Jack Kelly Clark
September-October 1995
Volume 49, Number 5

Peer-reviewed research and review articles

Long-term survival question: Why do oaks produce boom-and-bust seed crops?
by Walter D. Koenig, Jean Knops
| Full text HTML  | PDF  
Acorn production of California oaks correlates with weather conditions favorable for pollination and, in two species, rainfall 1 and 2 years prior o acorn fall.
Annual differences in acorn crop size of California oaks do not correlate with rainfall the year before, but instead with weather conditions favorable for pollination and, in two species, rainfall 1 and 2 years prior to acorn fall. Despite considerable differences in mean productivity, correlated in part with local differences in water and nutrient availability, acorn production by individual trees within populations are generally synchronous. Synchrony extends over fairly large geographic areas, although whether on a statewide scale is not yet known. Knowledge of acorn production patterns may facilitate conservation of oaks rangelands, improve our understanding of wildlife ecology and provide insights into the social structure of California's Native Americans.
Planted blue oaks may need help to survive in Southern Sierras
by Theodore E. Adams, Neil K. McDougald
| Full text HTML  | PDF  
Careful side selection, control of weed competition and protection from rodents may be needed to restock blue oaks on California rangelands.
Competition from annual herbaceous plants is one of many factors inhibiting establishment of blue oaks in California. Other factors include drought and large and small mammal depredation; gophers are a particularly serious threat to the seedling's emergence and survival. To measure the impact of these and other factors, a series of studies compared the emergence and survival of directly seeded acorns and 2-month-old nursery stock. Results show that careful site selection, control of competition, and protection from mammal predators may all be needed to promote success of restocking programs on California rangelands.
Blue oak acorns more viable in Madera County than Kern County
by Ralph L. Phillips, Neil K. McDougald, Douglas McCreary
| Full text HTML  | PDF  
Acorns from Madera County were larger and more of their seedlings emerged from the soil and at a faster rate.
Acorns from native blue oaks growing in Madera and Kern counties were evaluated for quality in this 2-year study. Acorns from Madera County were larger and more of their seedlings emerged from the soil and at a faster rate than acorns from Kern County. Insect infestation and disease in the acorns were not consistent during the study.
Optimizing tomato distribution to processors lifts profits little
by Catherine A. Durham, Richard J. Sexton, Joo Ho Song
| Full text HTML  | PDF  
Interregional transport of tomatoes for processing is excessive, but a study suggests that optimizing allocation would improve industry profit only 1.9%.
Tomatoes are often hauled long distances in Northern and Central California. Because production areas and processing facilities are not geographically well aligned, processors compete across relatively long distances to procure tomatoes. In this study of the field-to-processor distribution of processing tomatoes, a nonlinear programming model was developed to determine the optimal distribution of tomatoes from the 13 highest-producing counties to the 32 processing plants in the region. Results suggest that excessive interregional haulage of tomatoes occurs, but the additional industry profit from implementing the optimal allocation versus the estimated actual allocation was only 1.9%.
Consistent annual treatment helps future olive leaf spot control
by Beth L. Teviotdale, G. Steven Sibbett
| Full text HTML  | PDF  
One annual fungicide treatment should control olive leaf spot in most orchards, but a second spray may help where conditions favor disease development.
Tulare County research revealed that an orchard's disease history influences how well annual copper fungicide treatments will work in controlling olive leaf spot. Elevated disease levels are not easily reduced in 1 year, and consistent annual treatment is important for future disease control as well as for protection in the current year.
Leaf removal improves fungicide control of powdery mildew in SJV grapes
by James J. Stapleton, George M. Leavitt, Paul S. Verdegaal
| Full text HTML  | PDF  
On-farm experiments showed that leaf removal reduced powdery mildew and facilitated improved spray coverage in fruiting zones.
Basal leaf removal, which has been used to reduce damage from bunch rots and seasonal leafhopper infestations, was tested for its effects on powdery mildew in the San Joaquin Valley. Powdery mildew is one of the most damaging diseases of wine grapes in California. On-farm experiments showed that leaf removal reduced the disease in two of five experiments and facilitated improved spray coverage in grapevine fruiting zones. Leaf removal can improve the effectiveness of fungicide programs in reducing powdery mildew damage, but should not be relied upon alone to control the disease.
Farm labor contractors play new roles in agriculture
by Dawn Thilmany, Philip L. Martin
| Full text HTML  | PDF  
Growers say they find it easier and more cost-effective to use FLCs to recruit and supervise workers.
The role of farm labor contractors in California agriculture has evolved along with changes in the state's immigration and labor policies. Today, the role of FLCs in California is expanding, due in part to an increase in farm labor regulations. Growers say they find it easier and more cost-effective to use FLCs for the recruitment and supervision of agricultural workers. Yet the issue of who is liable for labor law violations and to what extent remains in dispute. This study investigates the changing relationship between FLCs and their grower-clients.

Editorial, News, Letters and Science Briefs

Competitive grants: Wave of the future?
by Henry J. Vaux
Full text HTML  | PDF  
Science Briefs
by Editors
Full text HTML  | PDF  
Urbanization crowds out oaks
by Editors
Full text HTML  | PDF  
Letters
From our readers
Full text HTML  | PDF  

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