California Agriculture, September-October 1995
Volume 49, Number 5
Oak rescue efforts: What have we learned?
peer-reviewed research articles
Long-term survival question: Why do oaks produce boom-and-bust seed crops?
by Walter D. Koenig , Jean Knops
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
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
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
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
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
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
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 & science briefs
Competitive grants: Wave of the future?
by Henry J. Vaux
Urbanization crowds out oaks
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