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California Agriculture, Vol. 47, No.5

Bt's at bloom may replace dormant sprays
Cover:  The insect pathogen Bacillus thuringiensis proved effective in controlling peach twig borer on almonds, peaches and nectarines, offering a possible alternative to dormant organophosphates. Watne Johnson, staff research associate at UC Davis, is shown spraying Bt in a Colusa County almond orchard. Photo by Jack Kelly Clark
September-October 1993
Volume 47, Number 5

Peer-reviewed research and review articles

Insect pathogen “Bt” controls peach twig borer on fruits and almonds
by William W. Barnett, John P. Edstrom, Richard L. Coviello, Frank P. Zalom
| Full text HTML  | PDF  
Results suggest growers can control peach twig borer using the insect pathogen Bt early in the season.
Early season sprays of the insect pathogen Bacillus thuringiensis, or “Bt,” were applied to peaches and almonds to determine efficacy against peach twig borer (PTB). Data indicates one or two Bt treatments during bloom are as effective as a dormant organo-phosphate plus oil spray for PTB control. Research is currently under way to determine the impact on other pests.
Why lacewings may fail to suppress aphids … Predators that eat other predators disrupt cotton aphid control
by Jay A. Rosenheim, Lawrence R. Wilhoit
| Full text HTML  | PDF  
The predatory green lacewing, Chrysoperla carnea, is often abundant in mid- and late-season cotton fields in the San Joaquin Valley. However, neither these natural populations nor insectary-reared and mass-released lace-wings appear to suppress populations of the cotton aphid. The key reason for the ineffectiveness of biological control appears to be the heavy mortality imposed on lacewing larvae by other generalist insect predators. Results of a study suggest that interactions between different species of insect predators may disrupt the biological control of pest species.
Biological control of the cotton aphid involves complex interactions among predators now under study.
Polymers check furrow erosion, help river life
by Hal McCutchan, Phil Osterli, John Letey
| Full text HTML  | PDF  
Polyacrylamides provide economic benefits and reduce pesticide residues carried by irrigation runoff into the San Joaquin River.
Each year, irrigation runoff from West Stanislaus County farmland carries about 1.2 million tons of sediment into the San Joaquin River. The sediment contains pesticide residues which threaten aquatic wildlife. One solution for this problem is to inject polyacrylamide polymers into irrigation water, a practice which reduces soil erosion and has economic benefits to the grower, such as increasing infiltration rates. In recent trials, this practice reduced soil erosion and runoff water from a furrow-irrigated spinach field. Polyacrylamide-treated furrows had a 10% lower outflow rate than the untreated furrows. In addition, the polyacrylamide flocculated the suspended soil particles; on average, 99.7% settled out compared to soil particles in untreated furrows.
In lettuce production, winter cover crops can decrease soil nitrate, leaching potential
by Louise E. Jackson, Lisa J. Wyland, Jill A. Klein, Richard F. Smith, William E. Chaney, Steven T. Koike
| Full text HTML  | PDF  
Nonlegumes grown as cover crops during the rainy fallow season reduced leachable nitrate in lettuce fields.
The large amounts of soil nitrate that can accumulate in annual row crop production during the winter fallow period can leach during winter storms and spring irrigation. In Monterey County, 48% of the wells in the upper unconfined aquifer exceed the public health drinking water standard of 10 ppm of nitrate-N. Nonleguminous cover crops, planted during the winter fallow and incorporated in early spring using reduced tillage equipment to maintain intact beds, have been found to reduce nitrate leaching without disrupting cropping schedules.
Adjusting sprinkler angle reduces spread of disease in pistachio
by Themis J. Michailides, David P. Morgan, William H. Olson, Joseph A. Grant
| Full text HTML  | PDF  
When sprinkler angle is set low, less water reaches the tree canopy, reducing spore release and dispersal.
During summer, especially in pistachio orchards irrigated with high-trajectory-angle sprinklers, sprinkler water spreads fungal inocula of Botryosphaeria blight disease to fruit clusters, shoots and leaves. In tests, altering the sprinkler irrigation trajectory angle from 23° to 12° prevented release and spread of spore inoculum and significantly reduced the disease in three commercial pistachio orchards in the Sacramento and San Joaquin valleys.
Crow damage to almonds increasing; no foolproof solution in sight
by Janine Hasey, Terrell P. Salmon
| Full text HTML  | PDF  
Sutter and Yuba almond growers report crow damage inflicts a 3 to 4% production loss.
Of all birds causing damage to almonds in Sutter and Yuba counties, crows cause the most, according to a survey of growers. Growers also reported they are willing to spend an average of $24 an acre to reduce damage by 50% within their orchards — far less than the potential value of nuts lost.
Berber orchardgrass tested as cover crop in commercial vineyard
by James A. Wolpert, Phil A. Phillips, R. K. Striegler, Michael V. McKenry, John H. Foott
| Full text HTML  | PDF  
Orchardgrass reduced vine growth, but did not increase vine yield; it lowered some insect and nematode populations.
A Berber orchardgrass cover crop reduced the growth and yield of Cabernet Sauvignon grapevines. Some nematode and arthropod pest populations were significantly lower in the cover crop plots; one was higher.
Shredding “mummy” walnuts is key to destroying navel orangeworm in winter
by G. Steven Sibbett, Robert A. Van Steenwyk
| Full text HTML  | PDF  
Simply removing mummy nuts from trees does not destroy overwintering larvae and pupae or prevent insect emergence.
Winter orchard sanitation is a major component of navel orangeworm (NOW) control in walnuts. “Mummy” nuts remaining in the trees shelter overwintering NOW. Once nuts are removed from the trees, shredding to destroy the protective shell ensures maximum NOW mortality.
Domestic, world market growing … Grape juice concentrate emerging as a sweetener in juices, food products
by Dale Heien, Ray Venner
| Full text HTML  | PDF  
Consumer preferences for fruit sweeteners over table sugar have strengthened an already growing concentrate market.
The domestic and world market for grape juice concentrate is growing. We discuss several options that may enable the San Joaquin Valley's grape industry to capture a larger share of this growth market.
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California Agriculture, Vol. 47, No.5

Bt's at bloom may replace dormant sprays
Cover:  The insect pathogen Bacillus thuringiensis proved effective in controlling peach twig borer on almonds, peaches and nectarines, offering a possible alternative to dormant organophosphates. Watne Johnson, staff research associate at UC Davis, is shown spraying Bt in a Colusa County almond orchard. Photo by Jack Kelly Clark
September-October 1993
Volume 47, Number 5

Peer-reviewed research and review articles

Insect pathogen “Bt” controls peach twig borer on fruits and almonds
by William W. Barnett, John P. Edstrom, Richard L. Coviello, Frank P. Zalom
| Full text HTML  | PDF  
Results suggest growers can control peach twig borer using the insect pathogen Bt early in the season.
Early season sprays of the insect pathogen Bacillus thuringiensis, or “Bt,” were applied to peaches and almonds to determine efficacy against peach twig borer (PTB). Data indicates one or two Bt treatments during bloom are as effective as a dormant organo-phosphate plus oil spray for PTB control. Research is currently under way to determine the impact on other pests.
Why lacewings may fail to suppress aphids … Predators that eat other predators disrupt cotton aphid control
by Jay A. Rosenheim, Lawrence R. Wilhoit
| Full text HTML  | PDF  
The predatory green lacewing, Chrysoperla carnea, is often abundant in mid- and late-season cotton fields in the San Joaquin Valley. However, neither these natural populations nor insectary-reared and mass-released lace-wings appear to suppress populations of the cotton aphid. The key reason for the ineffectiveness of biological control appears to be the heavy mortality imposed on lacewing larvae by other generalist insect predators. Results of a study suggest that interactions between different species of insect predators may disrupt the biological control of pest species.
Biological control of the cotton aphid involves complex interactions among predators now under study.
Polymers check furrow erosion, help river life
by Hal McCutchan, Phil Osterli, John Letey
| Full text HTML  | PDF  
Polyacrylamides provide economic benefits and reduce pesticide residues carried by irrigation runoff into the San Joaquin River.
Each year, irrigation runoff from West Stanislaus County farmland carries about 1.2 million tons of sediment into the San Joaquin River. The sediment contains pesticide residues which threaten aquatic wildlife. One solution for this problem is to inject polyacrylamide polymers into irrigation water, a practice which reduces soil erosion and has economic benefits to the grower, such as increasing infiltration rates. In recent trials, this practice reduced soil erosion and runoff water from a furrow-irrigated spinach field. Polyacrylamide-treated furrows had a 10% lower outflow rate than the untreated furrows. In addition, the polyacrylamide flocculated the suspended soil particles; on average, 99.7% settled out compared to soil particles in untreated furrows.
In lettuce production, winter cover crops can decrease soil nitrate, leaching potential
by Louise E. Jackson, Lisa J. Wyland, Jill A. Klein, Richard F. Smith, William E. Chaney, Steven T. Koike
| Full text HTML  | PDF  
Nonlegumes grown as cover crops during the rainy fallow season reduced leachable nitrate in lettuce fields.
The large amounts of soil nitrate that can accumulate in annual row crop production during the winter fallow period can leach during winter storms and spring irrigation. In Monterey County, 48% of the wells in the upper unconfined aquifer exceed the public health drinking water standard of 10 ppm of nitrate-N. Nonleguminous cover crops, planted during the winter fallow and incorporated in early spring using reduced tillage equipment to maintain intact beds, have been found to reduce nitrate leaching without disrupting cropping schedules.
Adjusting sprinkler angle reduces spread of disease in pistachio
by Themis J. Michailides, David P. Morgan, William H. Olson, Joseph A. Grant
| Full text HTML  | PDF  
When sprinkler angle is set low, less water reaches the tree canopy, reducing spore release and dispersal.
During summer, especially in pistachio orchards irrigated with high-trajectory-angle sprinklers, sprinkler water spreads fungal inocula of Botryosphaeria blight disease to fruit clusters, shoots and leaves. In tests, altering the sprinkler irrigation trajectory angle from 23° to 12° prevented release and spread of spore inoculum and significantly reduced the disease in three commercial pistachio orchards in the Sacramento and San Joaquin valleys.
Crow damage to almonds increasing; no foolproof solution in sight
by Janine Hasey, Terrell P. Salmon
| Full text HTML  | PDF  
Sutter and Yuba almond growers report crow damage inflicts a 3 to 4% production loss.
Of all birds causing damage to almonds in Sutter and Yuba counties, crows cause the most, according to a survey of growers. Growers also reported they are willing to spend an average of $24 an acre to reduce damage by 50% within their orchards — far less than the potential value of nuts lost.
Berber orchardgrass tested as cover crop in commercial vineyard
by James A. Wolpert, Phil A. Phillips, R. K. Striegler, Michael V. McKenry, John H. Foott
| Full text HTML  | PDF  
Orchardgrass reduced vine growth, but did not increase vine yield; it lowered some insect and nematode populations.
A Berber orchardgrass cover crop reduced the growth and yield of Cabernet Sauvignon grapevines. Some nematode and arthropod pest populations were significantly lower in the cover crop plots; one was higher.
Shredding “mummy” walnuts is key to destroying navel orangeworm in winter
by G. Steven Sibbett, Robert A. Van Steenwyk
| Full text HTML  | PDF  
Simply removing mummy nuts from trees does not destroy overwintering larvae and pupae or prevent insect emergence.
Winter orchard sanitation is a major component of navel orangeworm (NOW) control in walnuts. “Mummy” nuts remaining in the trees shelter overwintering NOW. Once nuts are removed from the trees, shredding to destroy the protective shell ensures maximum NOW mortality.
Domestic, world market growing … Grape juice concentrate emerging as a sweetener in juices, food products
by Dale Heien, Ray Venner
| Full text HTML  | PDF  
Consumer preferences for fruit sweeteners over table sugar have strengthened an already growing concentrate market.
The domestic and world market for grape juice concentrate is growing. We discuss several options that may enable the San Joaquin Valley's grape industry to capture a larger share of this growth market.

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