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California Agriculture, Vol. 55, No.5

Powering agriculture: UC builds energy alternatives
Cover:  Long before California's current energy crunch, UC scientists were working with growers and food processors to devise new ways for reducing energy usage in agriculture. At UC Davis, a methane generator called the APS-Digester is under construction that can digest multiple batches of animal manure and plant waste, a significant advance over the old "single-batch" systems; the resulting biogas can be used to produce energy. David R. Bartell welds one of APS-Digester's tanks. Photo by John Stumbos.
September-October 2001
Volume 55, Number 5

Peer-reviewed research and review articles

BIOS and conventional almond orchard management compared
by Walt J. Bentley, Lonnie Hendricks, Roger Duncan, Cressida Silvers, Lee Martin, Marcia Gibbs, Max Stevenson
| Full text HTML  | PDF  
Damage by navel orangeworm, peach twig borer and ants was measured, as well as natural pest predators and winter sanitation effectiveness.
Conventional almond growers in Merced and Stanislaus counties who use organophosphate, carb-amate and pyrethroid insecticides were compared with participants in the Biologically Integrated Orchard Systems (BIOS) program, who do not use these broad-spectrum insecticides. The results demonstrated consistent but not significantly lower infestation by navel orangeworm and peach twig borer for growers who used broad-spectrum sprays. Infestation by ants resulted in the most consistent difference between the two management practices, with significantly less damage when broad-spectrum sprays were used. The differences in overall pest damage were relatively minor, but the variation was greatest among those not using broad-spectrum sprays. Winter survival of the navel orangeworm parasitoid, Goniozus legneri, and parasitism by this beneficial insect were low in all orchards, sprayed or unsprayed. Winter removal of unharvested almonds to fewer than two per tree reduced navel orangeworm infestations in both treatments. Although many of the almond growers not using organo-phosphate, carbamate or pyrethroid sprays had less damage than some who used these materials, the greater range of damage experienced by these growers may explain why more almond growers prefer to use them annually to combat insect pests.
Armored scale insecticide resistance challenges San Joaquin Valley citrus growers
by Elizabeth Grafton-Cardwell, Yuling Ouyang, Rebecka Striggow, Stacy Vehrs
| Full text HTML  | PDF  
About 40% of the region's citrus scale are resistant to traditional insecticides; new products reduce scale but harm natural predators of secondary pests.
Organophosphate and carbamate insecticides have been used to treat citrus pest problems for more than 40 years. From 1990 to 1998, we documented California red scale and yellow scale resistance to these insecticides. Armored scale resistance is found on an estimated 40% of 163,000 acres of citrus in the San Joaquin Valley. Citrus growers have responded by either increasing their use of natural enemies, especially the parasitoid wasp Aphytis melinus, or by applying newly registered insect growth regulator or neonicotinoid insecticides. While the California red scale problem is, for the moment, greatly reduced, outbreaks of cottony cushion scale are occurring because the new insecticides are highly toxic to the predatory vedalia beetle.
Managing manure and conserving predators helps control flies in caged-layer poultry systems
by Bradley A. Mullens, Nancy C. Hinkle, Coralie E. Szijj, Douglas R. Kuney
| Full text HTML  | PDF  
Cleaning out of manure usually results in fly outbreaks; recolonizationof fresh manure by fly predators for biological control is relatively slow.
As the rural-urban interface expands, controlling flies has become increasingly important on California poultry farms. Manure management is a critical component of keeping fly populations in check. Recent research demonstrates that the dry pad left behind after manure cleanouts in cagedlayer poultry systems aids manure drying because of the elevation and improved airflow. Most mites and beetles that prey on fly eggs and larvae are removed in a cleanout, although predator populations require longer than flies to recover. Leaving undisturbed manure (with a larger number of predators) adjacent to recently removed manure did not improve fly control significantly in open-sided layer houses, but might be more important in fully enclosed houses.
Host-specific strain of Stemphylium causes leaf spot disease of California spinach
by Steven T. Koike, Diana M. Henderson, Edward E. Butler
| Full text HTML  | PDF  
A newly identified spinach disease, which closely resembles agrochemical damage, may have been misdiagnosed for several years.
The California spinach industry has grown dramatically over the past few decades; it now supplies well over 100,000 tons of various high-quality products to consumers. But a new foliar disease. Stemphylium leaf spot, can reduce spinach quality. After identifying this disease, we determined that the pathogen may also be a new, distinct strain of the fungus that is specific to spinach. Inoculation experiments demonstrated that numerous spinach lines are susceptible, including new downy mildew-resistant cultivars. Diagnosing this disease can be difficult because its symptoms often resemble damage from agrochemicals. Growers and pest control advisors should become familiar with the symptoms of the various foliar spinach diseases that occur in California because consumers of this crop tolerate only a small level of leaf spots and defects.
Rust disease continues to threaten California garlic crop
by Steven T. Koike, Richard F. Smith, R. Michael Davis, J. Joe Nunez, Ron E. Voss
| Full text HTML  | PDF  
Garlic rust became a major problem in 1998, following the wet El Niiio weather system. Caused by Puccinia a//ii,it can be controlled by several fungicides.
In 1998, following the very wet EI Niño weather event, a devastating outbreak of rust disease severely damaged the garlic crop in California. The disease also occurred in 1999 and 2000, indicating that rust may have developed into an annual problem. We identified the pathogen as Puccinia allii. In our study, it infected allium crops such as garlic, onion and chives, but not leek, elephant garlic or shallot. Currently registered materials did not control the disease, but tebuconazole (Folicur) and azoxystrobin (Quadris) provided good protection against garlic rust. Based on our work, a Section 18 emergency exomption for tebuconazole was approved by state pesticide regulators. We tested 34 UC and industry garlic varieties and found that none were completely resistant to garlic rust.
Interpersonal communication tops concerns of farm supervisors
by Gregory Encina Billikopf
| Full text HTML  | PDF  
Of 42 farm supervisors interviewed in the San Joaquin Valley, most gave their jobs high ratings but found it difficult to discipline and fire employees.
I interviewed 42 farm supervisors in the northern San Joaquin Valley, in order to explore how they became supervisors and how they feel about the work and deal with employee discipline. This study revealed that supervisors generally feel little need for additional training before they take on supervisory responsibilities. Like their farmworker counterparts, supervisors feel good about their jobs, rating them an average of 4.5 on a scale where 5 means the job is fantastic and 1 is terrible. When asked to identify the most challenging and rewarding aspects of their positions, farm supervisors overwhelmingly mentioned their relations with people. Those in upper management were more likely to have fired an employee than first-line supervisors, yet employee discipline was an important aspect of supervisors' work.
One-pass tillage equipment outstrips conventional tillage method
by Shrinivasa K. Upadhyaya, Kleber P. Lancas, Abilio G. Santos-Filho, Narendra S. Raghuwanshi
| Full text HTML  | PDF  
In field tests, one-pass tillage provided average fuel savings of 50% compared with conventional land preparationmethods, and time savings of 72%.
For this study, we compared a new one-pass tillage implement called the Incorpramaster with a conventional tillage practice of stubble disking and land planing. Our randomized block experiment on the UC Davis campus evaluated the equipment's energy and time savings. We found that the one-pass tillage equipment (OPTE) outperformed conventional land preparation methods in fuel consumption and speed. Fuel savings ranged from 19% to 81% with a mean savings of 50%. Time savings ranged from 67% to 83% with mean of 72%. The mean soil particle size created by the one-pass tillage implement was comparable to that produced by conventional tillage methods.
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California Agriculture, Vol. 55, No.5

Powering agriculture: UC builds energy alternatives
Cover:  Long before California's current energy crunch, UC scientists were working with growers and food processors to devise new ways for reducing energy usage in agriculture. At UC Davis, a methane generator called the APS-Digester is under construction that can digest multiple batches of animal manure and plant waste, a significant advance over the old "single-batch" systems; the resulting biogas can be used to produce energy. David R. Bartell welds one of APS-Digester's tanks. Photo by John Stumbos.
September-October 2001
Volume 55, Number 5

Peer-reviewed research and review articles

BIOS and conventional almond orchard management compared
by Walt J. Bentley, Lonnie Hendricks, Roger Duncan, Cressida Silvers, Lee Martin, Marcia Gibbs, Max Stevenson
| Full text HTML  | PDF  
Damage by navel orangeworm, peach twig borer and ants was measured, as well as natural pest predators and winter sanitation effectiveness.
Conventional almond growers in Merced and Stanislaus counties who use organophosphate, carb-amate and pyrethroid insecticides were compared with participants in the Biologically Integrated Orchard Systems (BIOS) program, who do not use these broad-spectrum insecticides. The results demonstrated consistent but not significantly lower infestation by navel orangeworm and peach twig borer for growers who used broad-spectrum sprays. Infestation by ants resulted in the most consistent difference between the two management practices, with significantly less damage when broad-spectrum sprays were used. The differences in overall pest damage were relatively minor, but the variation was greatest among those not using broad-spectrum sprays. Winter survival of the navel orangeworm parasitoid, Goniozus legneri, and parasitism by this beneficial insect were low in all orchards, sprayed or unsprayed. Winter removal of unharvested almonds to fewer than two per tree reduced navel orangeworm infestations in both treatments. Although many of the almond growers not using organo-phosphate, carbamate or pyrethroid sprays had less damage than some who used these materials, the greater range of damage experienced by these growers may explain why more almond growers prefer to use them annually to combat insect pests.
Armored scale insecticide resistance challenges San Joaquin Valley citrus growers
by Elizabeth Grafton-Cardwell, Yuling Ouyang, Rebecka Striggow, Stacy Vehrs
| Full text HTML  | PDF  
About 40% of the region's citrus scale are resistant to traditional insecticides; new products reduce scale but harm natural predators of secondary pests.
Organophosphate and carbamate insecticides have been used to treat citrus pest problems for more than 40 years. From 1990 to 1998, we documented California red scale and yellow scale resistance to these insecticides. Armored scale resistance is found on an estimated 40% of 163,000 acres of citrus in the San Joaquin Valley. Citrus growers have responded by either increasing their use of natural enemies, especially the parasitoid wasp Aphytis melinus, or by applying newly registered insect growth regulator or neonicotinoid insecticides. While the California red scale problem is, for the moment, greatly reduced, outbreaks of cottony cushion scale are occurring because the new insecticides are highly toxic to the predatory vedalia beetle.
Managing manure and conserving predators helps control flies in caged-layer poultry systems
by Bradley A. Mullens, Nancy C. Hinkle, Coralie E. Szijj, Douglas R. Kuney
| Full text HTML  | PDF  
Cleaning out of manure usually results in fly outbreaks; recolonizationof fresh manure by fly predators for biological control is relatively slow.
As the rural-urban interface expands, controlling flies has become increasingly important on California poultry farms. Manure management is a critical component of keeping fly populations in check. Recent research demonstrates that the dry pad left behind after manure cleanouts in cagedlayer poultry systems aids manure drying because of the elevation and improved airflow. Most mites and beetles that prey on fly eggs and larvae are removed in a cleanout, although predator populations require longer than flies to recover. Leaving undisturbed manure (with a larger number of predators) adjacent to recently removed manure did not improve fly control significantly in open-sided layer houses, but might be more important in fully enclosed houses.
Host-specific strain of Stemphylium causes leaf spot disease of California spinach
by Steven T. Koike, Diana M. Henderson, Edward E. Butler
| Full text HTML  | PDF  
A newly identified spinach disease, which closely resembles agrochemical damage, may have been misdiagnosed for several years.
The California spinach industry has grown dramatically over the past few decades; it now supplies well over 100,000 tons of various high-quality products to consumers. But a new foliar disease. Stemphylium leaf spot, can reduce spinach quality. After identifying this disease, we determined that the pathogen may also be a new, distinct strain of the fungus that is specific to spinach. Inoculation experiments demonstrated that numerous spinach lines are susceptible, including new downy mildew-resistant cultivars. Diagnosing this disease can be difficult because its symptoms often resemble damage from agrochemicals. Growers and pest control advisors should become familiar with the symptoms of the various foliar spinach diseases that occur in California because consumers of this crop tolerate only a small level of leaf spots and defects.
Rust disease continues to threaten California garlic crop
by Steven T. Koike, Richard F. Smith, R. Michael Davis, J. Joe Nunez, Ron E. Voss
| Full text HTML  | PDF  
Garlic rust became a major problem in 1998, following the wet El Niiio weather system. Caused by Puccinia a//ii,it can be controlled by several fungicides.
In 1998, following the very wet EI Niño weather event, a devastating outbreak of rust disease severely damaged the garlic crop in California. The disease also occurred in 1999 and 2000, indicating that rust may have developed into an annual problem. We identified the pathogen as Puccinia allii. In our study, it infected allium crops such as garlic, onion and chives, but not leek, elephant garlic or shallot. Currently registered materials did not control the disease, but tebuconazole (Folicur) and azoxystrobin (Quadris) provided good protection against garlic rust. Based on our work, a Section 18 emergency exomption for tebuconazole was approved by state pesticide regulators. We tested 34 UC and industry garlic varieties and found that none were completely resistant to garlic rust.
Interpersonal communication tops concerns of farm supervisors
by Gregory Encina Billikopf
| Full text HTML  | PDF  
Of 42 farm supervisors interviewed in the San Joaquin Valley, most gave their jobs high ratings but found it difficult to discipline and fire employees.
I interviewed 42 farm supervisors in the northern San Joaquin Valley, in order to explore how they became supervisors and how they feel about the work and deal with employee discipline. This study revealed that supervisors generally feel little need for additional training before they take on supervisory responsibilities. Like their farmworker counterparts, supervisors feel good about their jobs, rating them an average of 4.5 on a scale where 5 means the job is fantastic and 1 is terrible. When asked to identify the most challenging and rewarding aspects of their positions, farm supervisors overwhelmingly mentioned their relations with people. Those in upper management were more likely to have fired an employee than first-line supervisors, yet employee discipline was an important aspect of supervisors' work.
One-pass tillage equipment outstrips conventional tillage method
by Shrinivasa K. Upadhyaya, Kleber P. Lancas, Abilio G. Santos-Filho, Narendra S. Raghuwanshi
| Full text HTML  | PDF  
In field tests, one-pass tillage provided average fuel savings of 50% compared with conventional land preparationmethods, and time savings of 72%.
For this study, we compared a new one-pass tillage implement called the Incorpramaster with a conventional tillage practice of stubble disking and land planing. Our randomized block experiment on the UC Davis campus evaluated the equipment's energy and time savings. We found that the one-pass tillage equipment (OPTE) outperformed conventional land preparation methods in fuel consumption and speed. Fuel savings ranged from 19% to 81% with a mean savings of 50%. Time savings ranged from 67% to 83% with mean of 72%. The mean soil particle size created by the one-pass tillage implement was comparable to that produced by conventional tillage methods.

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