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California Agriculture, Vol. 47, No.6

Drought takes toll on native oaks
Cover:  Although well adapted to periodic drought, populations of three species of native oak suffered setbacks from the severe 6-year drought on the California Central Coast. This blue oak (Quercus douglasii) was photographed in Hastings Natural History Reservation in Carmel Valley. Photo by Norden H. (Dan) Cheetham
November-December 1993
Volume 47, Number 6

Peer-reviewed research and review articles

Drought takes toll on Central Coast's native oaks
by William Tietje, William Weitkamp, Wayne Jensen, Sergio Garcia
| Full text HTML  | PDF  
A survey conducted on Central Coast rangeland revealed that 6 years of drought is one more factor contributing to the death of native oaks.
From 1987 through 1992, California experienced one of the most widespread and severe droughts in the state's history. A survey conducted in three Central Coast counties during 1988–92, indicates that many native oak trees on rangelands succumbed to the drought. The smaller oak trees on poorer sites were most vulnerable.
Restricting flow of almonds to export markets may raise profits
by Julian M. Alston, Jason Christian, Juan R. Murua, Richard J. Sexton
| Full text HTML  | PDF  
While growers may obtain short-run gains by restricting exports, these may later be offset by a loss in market share.
California is the world's dominant producer of almonds. Statistical models of demand for almonds in the United States and six leading export markets suggest that California can raise revenues and profits in the short run by restricting Sales to major export markets. However, in the long run, Spain or other producers may offset those short-run gains by increasing production.
With fewer acres, more mechanization: California leads Spain in almond production, exports to world
by Juan Ramon Murua, Hoy Carman, Julian Alston
| Full text HTML  | PDF  
Almond producers here and abroad respond to similar factors; if California prices go up, so will world production.
With rapid expansion of almond acreage since the late 1960s, California has become the world's dominant almond producer and the major supplier in export markets. Spain, the world's number two producer, has more than three times California's acreage, but its comparatively low average yields have limited its penetration of export markets. This article examines differences in the two almond producers, particularly with regard to yield and response to economic incentives.
California's apple industry gets a new fresh look
by Hoy Carman
| Full text HTML  | PDF  
San Joaquin Valley growers are shifting to fresh market production of Granny Smith, Fuji, Gala and other new varieties.
A “new” apple industry based on fresh market sales of the Granny Smith, Fuji and Gala varieties has recently been established in California's Central Valley. Production, already significant, will continue to grow as new plantings reach maturity and additional investment in marketing infrastructure will be required.
Effectiveness of leafhopper control varies with lacewing release methods
by Kent M. Daane, Glenn Y. Yokota, Yvonne D. Rasmussen, Yuwei Zheng, Kenneth S. Hagen
| Full text HTML  | PDF  
New recommendations call for accurate monitoring of leafhopper densities and careful delivery of lacewing eggs.
Augmentative releases of green lacewings suppressed variegated grape leafhopper in experimental plots and commercial vineyards; however, effectiveness varied greatly. Field studies show that improved release methods and a better understanding of lacewing biology are needed to optimize commercial release programs.
Natural enemies of Russian wheat aphid identified in California
by J. Bernal, D. González, E. T. Natwick, J. G. Loya, R. León-Lopez, W. E. Bendixen
| Full text HTML  | PDF  
Research revealed natural enemies of Russian wheat aphid; their impact can be augmented by imported species.
A survey of natural enemies of Russian wheat aphid conducted over several growing seasons reveals a complex of predators and parasites attacking this pest in California cereal fields. Because of environmental and economic considerations, unilateral use of insecticides is not a sound management strategy against this pest. A number of promising natural enemies have been imported and are now being reared for release in California cereal fields. These natural enemies may augment the effectiveness of those already present in California.
When measuring soil water content, field practices affect neutron moisture meter accuracy
by Blaine R. Hanson, Gylan L. Dickey
| Full text HTML  | PDF  
The authors have developed guidelines for improving neutron moisture meter measurements.
Field practices for measuring soil water content with neutron moisture meters were assessed. One finding: Using meters of the same manufacturer with different components (such as different types of detector tubes) or meters of different manufacturers can greatly alter performance and affect results. Guidelines were developed for making standard counts and for making counts in the soil.
Controlling dodder in alfalfa hay calls for an integrated procedure
by Steve B. Orloff, David W. Cudney
| Full text HTML  | PDF  
Mowing and burning become increasingly important methods of dodder control as the alfalfa season progresses.
Dodder is a troublesome parasitic weed in alfalfa hay fields. Pre-emergence treatment with trifluralin controls dodder early in the season, but as the season progresses, control declines. Flail mowing escaped dodder patches in midseason followed by burning in late season, when dodder seed was being produced, was found to be an effective, integrated control procedure.
Controlled grazing on annual grassland decreases yellow starthistle
by Craig D. Thomsen, William A. Williams, Marc Vayssiéres, Fremont L. Bell, Melvin R. George
| Full text HTML  | PDF  
Properly timed grazing effectively manages starthistle infestations.
Livestock grazing in late spring and early summer resulted in large reductions of yellow starthistle, Centaurea solstitialis, on infested annual grasslands. Grazing in the bolting stage before spines developed reduced starthistle's canopy size, seed production and thatch accumulation and enhanced native plant diversity. Property timed grazing effectively manages starthistle on a seasonal basis but does not eliminate populations.

Editorial, News, Letters and Science Briefs

Agricultural, environmental issues need interdisciplinary approach
by Barbara Schneeman
Full text HTML  | PDF  
Webmaster Email: wsuckow@ucanr.edu

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California Agriculture, Vol. 47, No.6

Drought takes toll on native oaks
Cover:  Although well adapted to periodic drought, populations of three species of native oak suffered setbacks from the severe 6-year drought on the California Central Coast. This blue oak (Quercus douglasii) was photographed in Hastings Natural History Reservation in Carmel Valley. Photo by Norden H. (Dan) Cheetham
November-December 1993
Volume 47, Number 6

Peer-reviewed research and review articles

Drought takes toll on Central Coast's native oaks
by William Tietje, William Weitkamp, Wayne Jensen, Sergio Garcia
| Full text HTML  | PDF  
A survey conducted on Central Coast rangeland revealed that 6 years of drought is one more factor contributing to the death of native oaks.
From 1987 through 1992, California experienced one of the most widespread and severe droughts in the state's history. A survey conducted in three Central Coast counties during 1988–92, indicates that many native oak trees on rangelands succumbed to the drought. The smaller oak trees on poorer sites were most vulnerable.
Restricting flow of almonds to export markets may raise profits
by Julian M. Alston, Jason Christian, Juan R. Murua, Richard J. Sexton
| Full text HTML  | PDF  
While growers may obtain short-run gains by restricting exports, these may later be offset by a loss in market share.
California is the world's dominant producer of almonds. Statistical models of demand for almonds in the United States and six leading export markets suggest that California can raise revenues and profits in the short run by restricting Sales to major export markets. However, in the long run, Spain or other producers may offset those short-run gains by increasing production.
With fewer acres, more mechanization: California leads Spain in almond production, exports to world
by Juan Ramon Murua, Hoy Carman, Julian Alston
| Full text HTML  | PDF  
Almond producers here and abroad respond to similar factors; if California prices go up, so will world production.
With rapid expansion of almond acreage since the late 1960s, California has become the world's dominant almond producer and the major supplier in export markets. Spain, the world's number two producer, has more than three times California's acreage, but its comparatively low average yields have limited its penetration of export markets. This article examines differences in the two almond producers, particularly with regard to yield and response to economic incentives.
California's apple industry gets a new fresh look
by Hoy Carman
| Full text HTML  | PDF  
San Joaquin Valley growers are shifting to fresh market production of Granny Smith, Fuji, Gala and other new varieties.
A “new” apple industry based on fresh market sales of the Granny Smith, Fuji and Gala varieties has recently been established in California's Central Valley. Production, already significant, will continue to grow as new plantings reach maturity and additional investment in marketing infrastructure will be required.
Effectiveness of leafhopper control varies with lacewing release methods
by Kent M. Daane, Glenn Y. Yokota, Yvonne D. Rasmussen, Yuwei Zheng, Kenneth S. Hagen
| Full text HTML  | PDF  
New recommendations call for accurate monitoring of leafhopper densities and careful delivery of lacewing eggs.
Augmentative releases of green lacewings suppressed variegated grape leafhopper in experimental plots and commercial vineyards; however, effectiveness varied greatly. Field studies show that improved release methods and a better understanding of lacewing biology are needed to optimize commercial release programs.
Natural enemies of Russian wheat aphid identified in California
by J. Bernal, D. González, E. T. Natwick, J. G. Loya, R. León-Lopez, W. E. Bendixen
| Full text HTML  | PDF  
Research revealed natural enemies of Russian wheat aphid; their impact can be augmented by imported species.
A survey of natural enemies of Russian wheat aphid conducted over several growing seasons reveals a complex of predators and parasites attacking this pest in California cereal fields. Because of environmental and economic considerations, unilateral use of insecticides is not a sound management strategy against this pest. A number of promising natural enemies have been imported and are now being reared for release in California cereal fields. These natural enemies may augment the effectiveness of those already present in California.
When measuring soil water content, field practices affect neutron moisture meter accuracy
by Blaine R. Hanson, Gylan L. Dickey
| Full text HTML  | PDF  
The authors have developed guidelines for improving neutron moisture meter measurements.
Field practices for measuring soil water content with neutron moisture meters were assessed. One finding: Using meters of the same manufacturer with different components (such as different types of detector tubes) or meters of different manufacturers can greatly alter performance and affect results. Guidelines were developed for making standard counts and for making counts in the soil.
Controlling dodder in alfalfa hay calls for an integrated procedure
by Steve B. Orloff, David W. Cudney
| Full text HTML  | PDF  
Mowing and burning become increasingly important methods of dodder control as the alfalfa season progresses.
Dodder is a troublesome parasitic weed in alfalfa hay fields. Pre-emergence treatment with trifluralin controls dodder early in the season, but as the season progresses, control declines. Flail mowing escaped dodder patches in midseason followed by burning in late season, when dodder seed was being produced, was found to be an effective, integrated control procedure.
Controlled grazing on annual grassland decreases yellow starthistle
by Craig D. Thomsen, William A. Williams, Marc Vayssiéres, Fremont L. Bell, Melvin R. George
| Full text HTML  | PDF  
Properly timed grazing effectively manages starthistle infestations.
Livestock grazing in late spring and early summer resulted in large reductions of yellow starthistle, Centaurea solstitialis, on infested annual grasslands. Grazing in the bolting stage before spines developed reduced starthistle's canopy size, seed production and thatch accumulation and enhanced native plant diversity. Property timed grazing effectively manages starthistle on a seasonal basis but does not eliminate populations.

Editorial, News, Letters and Science Briefs

Agricultural, environmental issues need interdisciplinary approach
by Barbara Schneeman
Full text HTML  | PDF  

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