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July-August 1998

Cover: Seeding native plants stabilized the soil surface and surpressed blowing dust in the Antelope Valley. David Vaughn measures the percentage of ground covered by the shrubs and Indian ricegrass. Photo by Jack Rhyne

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California Agriculture, July-August 1998

Volume 52, Number 4
Taking measure of Dustbuster efforts

Peer-reviewed Research Articles

DustBusters reduce pollution, wind erosion: Though difficult to achieve, revegetation is best way to stabilize soil
by David A. Grantz, David L. Vaughn, Robert J. Farber, Bong Kim, Tony VanCuren, Rich Campbell, David Bainbridge, Tom Zink
pp8-13, doi#10.3733/ca.v052n04p8
Abstract
Surface disturbance in arid regions — whether it results from abandoned agriculture, overgrazing or recreational activities — often sets the stage for windblown fugitive dust. Revegetation provides the most sustainable soil stabilization but is difficult to achieve in any given year. Widely varying environmental conditions and soil factors make direct seeding unreliable, and transplanting of nursery-grown shrubs does not assure plant establishment, even with supplemental irrigation. In occasional years plants can be successfully established, particularly Atriplex canescens, in the western Mojave Desert. Once vegetation becomes established, it successfully stabilizes the soil surface and reduces blowing dust. However, because successful establishment is infrequent, reliable mitigation of fugitive dust requires that other techniques be used as well.
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Wind barriers offer short-term solution to fugitive dust
by David A. Grantz, David L. Vaughn, Robert J. Farber, Bong Kim, Tony VanCuren, Rich Campbell
pp14-18, doi#10.3733/ca.v052n04p14
Abstract
Wind-blown fugitive dust is a widespread problem in the arid west resulting from land disturbance or abandonment and increasingly limited water supplies. Soil-derived particles obstruct visibility, cause property damage and contribute to violations of health-based air quality standards for fine particles (PM-10). These dry lands are often difficult to revegetate, yet they may require immediate stabilization. We evaluated the effectiveness of three types of mechanical wind barriers, which can be Installed more rapidly and more reliably than revegetation, in suppressing dust emissions. Wind fences, furrows and scattered roughness elements, such as plastic cones, are shown to reduce fugitive dust emissions in areas of the Mojave Desert that resisted revegetation.
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Grape growers report losses to black-foot and grapevine decline
by Heather Scheck, Stephen Vasquez, Diana Fogle, W. Douglas Gubler
pp19-23, doi#10.3733/ca.v052n04p19
Abstract
Sporadic but increasing incidence of two new diseases, which we have named “black-foot disease” and “Phaeoacremonium grapevine decline,” are taking a toll in California's table and wine grape vineyards (Scheck et al 1998a, 1998b). Although the full scope of the problem is not yet measured, grape growers throughout major production regions in California have reported economic losses from replanting costs. Symptoms of these diseases are almost indistinguishable from each other; the diseases are in fact the same that have occurred in grapevines in other places in the world and in older grapevines here. Our research reveals that black-foot is caused by Cylindrocarpon obtusisporum, and grapevine decline is caused by Phaeoacremonium species (P. aleophilum, P. chlamydosporum, or P. inflatipes).
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Verticillium survives heat in Mojave Desert alfalfa
by Donald C. Erwin, Amy B. Howell
pp24-26, doi#10.3733/ca.v052n04p24
Abstract
Verticillium albo-atrum, the cause of Verticillium wilt of alfalfa, was detected consistently in 1989 and 1990 in alfalfa stems collected from a farm in the Mojave Desert at air temperatures (up to 104°F) above the maximum (86°F) for its growth and sporulation. According to research in other areas of the United States and in Canada, infected alfalfa hay is a prime source of inoculum. Resistance to Verticillium wilt in nondormant germplasms was readily developed by selection in six germplasms that have been released.
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Pest management record-keeping duties shift with computerization
by Mary Louise Flint, Eileen Cullen, Eric Zilbert, Frank G. Zalom, Gene Miyao, Richard Coviello
pp27-31, doi#10.3733/ca.v052n04p27
Abstract
Computer software has been widely adopted in the tomato processing industry for maintaining pest management records. Although computers have not reduced the time necessary to complete record-keeping requirements, they have shifted some of the burden from growers to pest control advisers (PCAs). Most records kept are pesticide use records required by law or by processors, and the legally required written recommendation. There is little evidence that computer software is being used to maintain or analyze field scouting data.
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Latinos improve food habits through nutrition education
by Lucia L. Kaiser, Jeanette M. Sutherlin, Sallie C. Yoshida, Suzanne P. Murphy, Stuart D. Bresnick
pp32-35, doi#10.3733/ca.v052n04p32
Abstract
Identifying the health concerns and barriers to change of diverse audiences is essential to successful nutrition interventions that reduce the risk of chronic disease. This article reports some of the current activities that the Expanded Food and Nutrition Education Program (EFNEP) is undertaking in California to assess the needs of Latino clients and to develop culturally appropriate tools to evaluate changes in food-related behaviors. Latinos in Fresno County reported a number of improvements in food-related behaviors after attending EFNEP nutrition classes, particularly in the areas of reducing fat intake, using a wider variety of fruits and vegetables, shopping wisely and thawing meat safely. Nutrition educators working with Latinos need to find new ways to reach more family members, possibly including classes that involve spouses, newsletters and Spanish radio programs.
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Celery petiole lesion damage caused by insecticide
by Steven T. Koike, Richard F. Smith, Kurt F. Schulbach, William E. Chaney
pp36-40, doi#10.3733/ca.v052n04p36
Abstract
A previously undiagnosed problem, called celery petiole lesion (CPL), caused significant damage to coastal celery for several years. A 2-year study found CPL to be associated with applications of the insecticide Dibrom. The product is no longer labeled for use on celery. CPL can be mistaken for two fungal diseases, highlighting the importance of accurate diagnosis of plant problems to reduce unnecessary applications of pesticides.
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Editorial, News, Letters and Science briefs

EDITORIAL: Potpourri: New strategies, funding, partnerships
by W.R. Gomes
pp2, doi#10.3733/ca.v052n04p2
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Science briefs
Editors
pp4-5, doi#10.3733/ca.v052n04p4
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Scientists score dustbusting efforts in Antelope Valley
Editors
pp6, doi#10.3733/ca.v052n04p6
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Summer boating main source of lake's MTBE
Editors
pp7, doi#10.3733/ca.v052n04p7
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Ecology of a blackberry-leafhopper-parasite system and its relevance to California grape agroecosystems

by D. W. Williams
pp1-32, doi#10.3733/hilg.v52n04p032
Abstract
Natural ecosystems are often sources of pest arthropods and their natural enemies for nearby agroecosystems. This study treats the ecology of the native California blackberry, Rubus ursinus Cham. and Schlecht, and an imported blackberry, Rubus procerus P.J. Mueller, the blackberry leaf-hopper (BLH), Dikrella califomica (Lawson), and its egg parasite, Anagrus epos Girault, in two riparian habitats and a vineyard site. Anagrus is also an effective natural enemy of the grape leafhopper (GLH), Erythroneura elegantula Osborn, which evolved on wild grape in the riparian habitat and became a serious pest after the introduction of commercial varieties. The parasite overwinters in immature stages in the eggs of BLH in blackberry. In the early spring, growth of the native blackberry and BLH oviposition precede grape growth and GLH oviposition by the length of one parasite generation. Since Anagrus becomes active when BLH oviposition begins, this synchrony allows the parasite to increase its populations in the riparian refuge before entering the vineyard. The two blackberry species differ in their preferred habitats: the native blackberry is limited to moist shady habitats, while the imported species grows in open sunlit areas. In phenology the imported blackberry appears less synchronized with and less constrained by the California climate. The blackberry leafhopper produces three generations per year and overwinters as a diapausing adult. The leafhopper is well adapted to the phenology of the native blackberry, but less so to that of the imported species, which breaks dormancy in the spring long after BLH terminates diapause. Leafhopper females oviposit primarily in the lower half of the leaf canopy of the native blackberry throughout the season, while in the imported species they shift oviposition from the top of the canopy in early spring to the bottom by late summer. A time-varying life table analysis shows that BLH immature mortality due to Anagrus, nymphal parasites, and general predators is positively density dependent. Age-specific life table analyses in the laboratory estimate that Anagrus' intrinsic rate of increase (rm) is 2.2 times those of BLH and GLH. Although rm is a questionable index of parasite effectiveness, the difference probably allows Anagrus to respond rapidly to changes in GLH populations. Suggestions for the further augmentation of Anagrus populations in artificial refuges includes the management of blackberry and the monitoring and maintenance of BLH populations.
PDF

Ecology of a blackberry-leafhopper-parasite system and its relevance to California grape agroecosystems

by D. W. Williams
pp1-32, doi#10.3733/hilg.v52n04p032
Abstract
Natural ecosystems are often sources of pest arthropods and their natural enemies for nearby agroecosystems. This study treats the ecology of the native California blackberry, Rubus ursinus Cham. and Schlecht, and an imported blackberry, Rubus procerus P.J. Mueller, the blackberry leaf-hopper (BLH), Dikrella califomica (Lawson), and its egg parasite, Anagrus epos Girault, in two riparian habitats and a vineyard site. Anagrus is also an effective natural enemy of the grape leafhopper (GLH), Erythroneura elegantula Osborn, which evolved on wild grape in the riparian habitat and became a serious pest after the introduction of commercial varieties. The parasite overwinters in immature stages in the eggs of BLH in blackberry. In the early spring, growth of the native blackberry and BLH oviposition precede grape growth and GLH oviposition by the length of one parasite generation. Since Anagrus becomes active when BLH oviposition begins, this synchrony allows the parasite to increase its populations in the riparian refuge before entering the vineyard. The two blackberry species differ in their preferred habitats: the native blackberry is limited to moist shady habitats, while the imported species grows in open sunlit areas. In phenology the imported blackberry appears less synchronized with and less constrained by the California climate. The blackberry leafhopper produces three generations per year and overwinters as a diapausing adult. The leafhopper is well adapted to the phenology of the native blackberry, but less so to that of the imported species, which breaks dormancy in the spring long after BLH terminates diapause. Leafhopper females oviposit primarily in the lower half of the leaf canopy of the native blackberry throughout the season, while in the imported species they shift oviposition from the top of the canopy in early spring to the bottom by late summer. A time-varying life table analysis shows that BLH immature mortality due to Anagrus, nymphal parasites, and general predators is positively density dependent. Age-specific life table analyses in the laboratory estimate that Anagrus' intrinsic rate of increase (rm) is 2.2 times those of BLH and GLH. Although rm is a questionable index of parasite effectiveness, the difference probably allows Anagrus to respond rapidly to changes in GLH populations. Suggestions for the further augmentation of Anagrus populations in artificial refuges includes the management of blackberry and the monitoring and maintenance of BLH populations.
PDF

Ecology of a blackberry-leafhopper-parasite system and its relevance to California grape agroecosystems

by D. W. Williams
pp1-32, doi#10.3733/hilg.v52n04p032
Abstract
Natural ecosystems are often sources of pest arthropods and their natural enemies for nearby agroecosystems. This study treats the ecology of the native California blackberry, Rubus ursinus Cham. and Schlecht, and an imported blackberry, Rubus procerus P.J. Mueller, the blackberry leaf-hopper (BLH), Dikrella califomica (Lawson), and its egg parasite, Anagrus epos Girault, in two riparian habitats and a vineyard site. Anagrus is also an effective natural enemy of the grape leafhopper (GLH), Erythroneura elegantula Osborn, which evolved on wild grape in the riparian habitat and became a serious pest after the introduction of commercial varieties. The parasite overwinters in immature stages in the eggs of BLH in blackberry. In the early spring, growth of the native blackberry and BLH oviposition precede grape growth and GLH oviposition by the length of one parasite generation. Since Anagrus becomes active when BLH oviposition begins, this synchrony allows the parasite to increase its populations in the riparian refuge before entering the vineyard. The two blackberry species differ in their preferred habitats: the native blackberry is limited to moist shady habitats, while the imported species grows in open sunlit areas. In phenology the imported blackberry appears less synchronized with and less constrained by the California climate. The blackberry leafhopper produces three generations per year and overwinters as a diapausing adult. The leafhopper is well adapted to the phenology of the native blackberry, but less so to that of the imported species, which breaks dormancy in the spring long after BLH terminates diapause. Leafhopper females oviposit primarily in the lower half of the leaf canopy of the native blackberry throughout the season, while in the imported species they shift oviposition from the top of the canopy in early spring to the bottom by late summer. A time-varying life table analysis shows that BLH immature mortality due to Anagrus, nymphal parasites, and general predators is positively density dependent. Age-specific life table analyses in the laboratory estimate that Anagrus' intrinsic rate of increase (rm) is 2.2 times those of BLH and GLH. Although rm is a questionable index of parasite effectiveness, the difference probably allows Anagrus to respond rapidly to changes in GLH populations. Suggestions for the further augmentation of Anagrus populations in artificial refuges includes the management of blackberry and the monitoring and maintenance of BLH populations.
PDF