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California Agriculture, Vol. 54, No.6

Special Section: IPM evolves to battle new pests
Cover:  Several stages of red gum lerp psyllid, one of the newest eucalpytus pests. Inset, entomologist Don Dahlsten checks a trap to monitor the adult psyllid and its parasitoid. Photos by Jack Kelly Clark.
November-December 2000
Volume 54, Number 6

Peer-reviewed research and review articles

UC scientists apply IPM techniques to new eucalyptus pests
by Timothy D. Paine, Donald L. Dahlsten, Jocelyn G. Millar, Mark S. Hoddle, Lawrence M. Hanks
| Full text HTML  | PDF  
IPM strategies combat the recently intro- duced eucalyptus pests red gum lerp psyl lid and eucalyptus tortoise beetle.
Eucalyptus trees have been important components of the California urban landscape for almost 150 years. Until 1984, they were free of both insect and disease pests. In the last 16 years, however, a series of herbivorous insect species have been introduced into the state, probably accidentally, causing significant damage to the trees. Research programs have provided solutions to some of these pest problems, but more pests are continually introduced, recently the red gum lerp psyllid, the lemon gum lerp psyllid, and the eucalyptus tortoise beetle. Scientists are developing new strategies to control the recent invaders in concert with existing pest management programs, integrating methods across broad geographic, horticultural and economic scales.
Almond and stone fruit growers reduce OP, increase pyrethroid use in dormant sprays
by Lynn Epstein, Susan Bassein, Frank G. Zalom
| Full text HTML  | PDF  
Pesticide use reports from 1992 to 1998 show a decline in organophosphate use in dormant almond and stone fruit orchards.
Growers and pesticide applicators in California are legally required to file pesticide use reports with details about every application to commercial crops. We used the individual applicator records to document a decline in the use of organophosphate pesticides (OP) on almond and stone fruit orchards during the rainy season in California, a time period in which the trees are dormant. The decline is important because dormant applications are a major source of surface water contamination and the Federal Clean Water Act mandates a reduction in movement of OPs into surface water. However, the decline in use of OPs has been accompanied by an increase in use of pyrethroid pesticides, particularly in stone fruit orchards. Additional implementation of “reduced-risk” integrated pest management practices could further reduce use of dormant applications of OPs and pyrethroids on almonds and stone fruit orchards.
IPM research profiled: 10-year trends
by Karen-Klonsky, Ben Shouse
Full text HTML  | PDF  
Mass releases of Trichogramma wasps can reduce damage from codling moth
by Nick Mills, Carolyn Pickel, Sarah Mansfield, Sandra McDougall, Rick Buchner, Janet Caprile, John Edstrom, Rachel Elkins, Janine Hasey, Kathy Kelley, Bill Krueger, Bill Olson, Russ Stocker
| Full text HTML  | PDF  
Wasps can be used to reduce codling moth damage by 60% in walnut and pome fruit orchards.
Mass releases of commercially produced Trichogramma wasps can be used to reduce damage from codling moth by 60% in walnut and pome fruit orchards in California. Results from field trials indicate that release rate and evenness of distribution are important factors influencing the effectiveness of wasp releases, and that damage reduction is more effective in walnuts and pears than in apples. Because the environmental risks of large-scale releases of Trichogramma wasps are likely to be small, wasp releases could be integrated with pheromone-based mating disruption for effective management of codling moth.
Cotton aphid emerges as major pest in SJV cotton
by Larry D. Godfrey, Jay A. Rosenheim, Peter B. Goodell
| Full text HTML  | PDF  
A better understanding of cotton aphid biology is helping growers adjust their practices to control this new pest.
During the 1990s, the cotton aphid (Aphis gossypii Glover) escalated from an occasional pest to an annual, severe pest of San Joaquin Valley (SJV) cotton. Although the cotton aphid is not a new insect in the SJV, the change in the bionomics of this pest dictated that new research efforts be directed toward its biology, damage thresholds and management. The 1980s saw major shifts in agronomic practices. For example, the introduction of a plant growth regulator allowed growers to promote vigorous plant growth, rather than limiting growth and yield potential through the practice of water and nitrogen stress. Recent field research has shown that applying high rates of nitrogen to cotton plants increases cotton aphid reproductive rates and can create conditions favorable to aphid outbreaks. The new practice of promoting vigorous growth may have created an optimal host plant environment for cotton aphid reproduction and survival. In addition, the shift to using pyrethroids to control other arthropod pests has enhanced the buildup of cotton aphid populations. The severe aphid outbreak during the 1995 cotton growing season served as a focal point to bring the industry together to discuss the status of cotton integrated pest management and to plan future directions. Results of this effort include increased awareness, greater understanding of cotton aphid biology and improved pest management decisions.
Integrated strategies offer site-specific control of yellow starthistle
by Joseph M. DiTomaso, Steven F. Enloe, Guy B. Kyser, Steve B. Orloff
| Full text HTML  | PDF  
Mowing, grazing, clover plantings, insects, prescribed burning and selective applica- tions of herbicides help with control.
Ongoing research projects integrate chemical, mechanical, cultural and biological techniques to control yellow starthistle, a prolific weed now infesting between 10 million and 15 million acres in California. With many options available to land managers, developing a long-term, strategic management plan most suitable to a specific area can be complicated. It requires careful consideration of the advantages and disadvantages of each option and how best to incorporate appropriate ones into an effective program. Management strategies include timely mowings, grazing, clover plantings, biological control insects, prescribed burning and selective applications of herbicides. In addition to new developments in the management of yellow starthistle, public awareness of invasive weed issues has translated into major legislative changes that should encourage and assist private and public landowners and managers to initiate long-term programs to prevent and manage invasive weeds, particularly yellow starthistle.
Interplanting grasses into alfalfa controls weeds in older stands
by Timothy S. Prather, W. Thomas Lanini, Steve Orloff, Ronald Vargas, Jerry L. Schmierer, W. Mick Canevari, Shannon Mueller, Warren Bendixen, Rose L. Krebill-Prather
| Full text HTML  | PDF  
Planting grasses into older alfalfa stands reduces weeds and suppresses alfalfa weevil populations.
Interplanting grasses into alfalfa effectively uses grass competition to reduce the amount of weeds in alfalfa hay. The increased production offsets a lower price for the hay content, making the alfalfa-grass hay equally profitable to alfalfa hay sprayed with herbicide. This technique avoids plant-back restrictions from use of some herbicides. Alfalfa weevil populations can be reduced below threshold levels, providing additional benefit from the technique. The percentage of growers interplanting did not change but nearly half of the 24% of growers using interplanting are new users of the technique. Cooperative Extension was viewed as the most useful source for interplanting information by 64% of farmers surveyed.
Solarization and biofumigation help disinfest soil
by James J. Stapleton, Clyde L. Elmore, James E. DeVay
| Full text HTML  | PDF  
Soil solarization and biofumigation can help disinfest soil in certain cases when methyl bromide becomes unavailable.
Preplant soil fumigation with methyl bromide is scheduled to be phased out by 2005. Chemical and nonchemical alternatives are being researched and identified. Soil solarization and/or biofumigation can help fill the gap in certain cases. These alternative methods of soil disinfestation are also of value to organic growers, home gardeners and others who will not or cannot use the soil fumigation chemicals employed by many conventional commercial growers.
Analysis shows climate-caused decreases in Scott River fall flows
by Daniel J. Drake, Kenneth W. Tate, Harry Carlson
| Full text HTML  | PDF  
Knowing that fall flows in the Scott River are primarily climatecontrolled may be useful for making water management decisions.
Because of declining anadromous fisheries, resource managers are concerned about the timing and quantity of water flows in Northern California's Scott River. We analyzed 48 years of flow and precipitation data to improve our collective understanding of the Scott River fall flow regime and to provide information for current and future fisheries-restoration efforts. Fall flows are primarily controlled by the water content of snow and precipitation during the previous 12 months. These two factors account for nearly 80% of the variation in fall flows. Our analysis shows that downward trends in fall flows appear to be explained by a decrease in the water content of the snow falling on the Scott River watershed. This information will be useful in assessing the relative benefits of conservation and restoration strategies against the larger background of climate-caused changes in river flow.
Algal-bacterial treatment facility removes selenium from drainage water
by Nigel W.T. Quinn, Terrance Leighton, Tryg J. Lundquist, F. Bailey Green, Max A. Zárate, William J. Oswald
| Full text HTML  | PDF  
The best-performing algal-bacterial selenium removal plant reduced nitrate by more than 95% and reduced selenium by 80%.
Growers and pesticide applicators in California are legally required to file pesticide use reports with details about every application to commercial crops. We used the individual applicator records to document a decline in the use of organophosphate pesticides (OP) on almond and stone fruit orchards during the rainy season in California, a time period in which the trees are dormant. The decline is important because dormant applications are a major source of surface water contamination and the Federal Clean Water Act mandates a reduction in movement of OPs into surface water. However, the decline in use of OPs has been accompanied by an increase in use of pyrethroid pesticides, particularly in stone fruit orchards. Additional implementation of “reduced-risk” integrated pest management practices could further reduce use of dormant applications of OPs and pyrethroids on almonds and stone fruit orchards.
Nutrition lessons improve Hispanic teenage girls' knowledge
by Michelle R. Neyman, Gladys Block, Jennifer L. Morris, Sheri Zidenberg-Cherr
| Full text HTML  | PDF  
Nutrition education improved the nutrition knowledge of many girls, but had little effect on their eating habits.
Nutrition knowledge and dietary intake among Hispanic teenage girls were assessed before and after a nutrition education intervention. We found that subjects were consuming several important nutrients at levels below current government recommendations. On average, Hispanic teenage girls consumed folate, calcium, zinc and iron at levels that were 40%, 36%, 18% and 8% below current recommendations, respectively. Participation in the five-lesson nutrition education program resulted in a 50% increase in nutrition knowledge and modest changes in dietary behavior; we observed improved dietary intake of vitamin C. Long-term interventions are needed to improve dietary habits as one means of enhancing overall health.
Tuolumne County shops capture local dollars
by Joan Wright, George Goldman, Nancy Feldman, Andrew Murray
| Full text HTML  | PDF  
A survey of consumers shows that local businesses are capturing more local dollars than 8 years earlier.
Tuolumne County retail merchants think that they are not capturing the lion's share of local sales, but they are! County residents do not go out of the county to shop as much as businesses think. A survey conducted in 1997 by the UC Cooperative Extension Office in Tuolumne County surveyed shoppers and checked perceptions of local business owners. The survey found that the proportion of money that is spent out of the county is not as high as businesses surmised. This follow-up to a similar study conducted in 1989 also showed that businesses are capturing more local dollars than they were 8 years earlier.
Grading error reduces grower incentives to increase prune quality
by James A. Chalfant, Jennifer S. James, Nathalie Lavoie, Richard J. Sexton
| Full text HTML  | PDF  
Because grading error tends to reward smaller prunes, growers have less incentive to produce larger prunes.
Grading is important to ensure the production of high-quality foods, but it is usually done with error, distorting market signals and diminishing incentives to produce high-quality products. Size is the main quality criterion for dried prunes and the crucial characteristic in determining prune value. We studied the economic effects of errors in commodity grading, focusing in particular on the implications of one-way (asymmetric) grading errors, namely when small, low-quality product is erroneously classified as high quality, but not vice versa. In an application to the California prune industry, we estimated the extent to which large prunes are undervalued and small prunes are overvalued. We conclude that grading error means that prunes graded as high-quality may not really be high-quality prunes. The presence of these incorrectly graded prunes depresses the prices that growers are paid for high-quality prunes and increases the net returns for small prunes. As a result, growers face reduced incentives to produce larger prunes.
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California Agriculture, Vol. 54, No.6

Special Section: IPM evolves to battle new pests
Cover:  Several stages of red gum lerp psyllid, one of the newest eucalpytus pests. Inset, entomologist Don Dahlsten checks a trap to monitor the adult psyllid and its parasitoid. Photos by Jack Kelly Clark.
November-December 2000
Volume 54, Number 6

Peer-reviewed research and review articles

UC scientists apply IPM techniques to new eucalyptus pests
by Timothy D. Paine, Donald L. Dahlsten, Jocelyn G. Millar, Mark S. Hoddle, Lawrence M. Hanks
| Full text HTML  | PDF  
IPM strategies combat the recently intro- duced eucalyptus pests red gum lerp psyl lid and eucalyptus tortoise beetle.
Eucalyptus trees have been important components of the California urban landscape for almost 150 years. Until 1984, they were free of both insect and disease pests. In the last 16 years, however, a series of herbivorous insect species have been introduced into the state, probably accidentally, causing significant damage to the trees. Research programs have provided solutions to some of these pest problems, but more pests are continually introduced, recently the red gum lerp psyllid, the lemon gum lerp psyllid, and the eucalyptus tortoise beetle. Scientists are developing new strategies to control the recent invaders in concert with existing pest management programs, integrating methods across broad geographic, horticultural and economic scales.
Almond and stone fruit growers reduce OP, increase pyrethroid use in dormant sprays
by Lynn Epstein, Susan Bassein, Frank G. Zalom
| Full text HTML  | PDF  
Pesticide use reports from 1992 to 1998 show a decline in organophosphate use in dormant almond and stone fruit orchards.
Growers and pesticide applicators in California are legally required to file pesticide use reports with details about every application to commercial crops. We used the individual applicator records to document a decline in the use of organophosphate pesticides (OP) on almond and stone fruit orchards during the rainy season in California, a time period in which the trees are dormant. The decline is important because dormant applications are a major source of surface water contamination and the Federal Clean Water Act mandates a reduction in movement of OPs into surface water. However, the decline in use of OPs has been accompanied by an increase in use of pyrethroid pesticides, particularly in stone fruit orchards. Additional implementation of “reduced-risk” integrated pest management practices could further reduce use of dormant applications of OPs and pyrethroids on almonds and stone fruit orchards.
IPM research profiled: 10-year trends
by Karen-Klonsky, Ben Shouse
Full text HTML  | PDF  
Mass releases of Trichogramma wasps can reduce damage from codling moth
by Nick Mills, Carolyn Pickel, Sarah Mansfield, Sandra McDougall, Rick Buchner, Janet Caprile, John Edstrom, Rachel Elkins, Janine Hasey, Kathy Kelley, Bill Krueger, Bill Olson, Russ Stocker
| Full text HTML  | PDF  
Wasps can be used to reduce codling moth damage by 60% in walnut and pome fruit orchards.
Mass releases of commercially produced Trichogramma wasps can be used to reduce damage from codling moth by 60% in walnut and pome fruit orchards in California. Results from field trials indicate that release rate and evenness of distribution are important factors influencing the effectiveness of wasp releases, and that damage reduction is more effective in walnuts and pears than in apples. Because the environmental risks of large-scale releases of Trichogramma wasps are likely to be small, wasp releases could be integrated with pheromone-based mating disruption for effective management of codling moth.
Cotton aphid emerges as major pest in SJV cotton
by Larry D. Godfrey, Jay A. Rosenheim, Peter B. Goodell
| Full text HTML  | PDF  
A better understanding of cotton aphid biology is helping growers adjust their practices to control this new pest.
During the 1990s, the cotton aphid (Aphis gossypii Glover) escalated from an occasional pest to an annual, severe pest of San Joaquin Valley (SJV) cotton. Although the cotton aphid is not a new insect in the SJV, the change in the bionomics of this pest dictated that new research efforts be directed toward its biology, damage thresholds and management. The 1980s saw major shifts in agronomic practices. For example, the introduction of a plant growth regulator allowed growers to promote vigorous plant growth, rather than limiting growth and yield potential through the practice of water and nitrogen stress. Recent field research has shown that applying high rates of nitrogen to cotton plants increases cotton aphid reproductive rates and can create conditions favorable to aphid outbreaks. The new practice of promoting vigorous growth may have created an optimal host plant environment for cotton aphid reproduction and survival. In addition, the shift to using pyrethroids to control other arthropod pests has enhanced the buildup of cotton aphid populations. The severe aphid outbreak during the 1995 cotton growing season served as a focal point to bring the industry together to discuss the status of cotton integrated pest management and to plan future directions. Results of this effort include increased awareness, greater understanding of cotton aphid biology and improved pest management decisions.
Integrated strategies offer site-specific control of yellow starthistle
by Joseph M. DiTomaso, Steven F. Enloe, Guy B. Kyser, Steve B. Orloff
| Full text HTML  | PDF  
Mowing, grazing, clover plantings, insects, prescribed burning and selective applica- tions of herbicides help with control.
Ongoing research projects integrate chemical, mechanical, cultural and biological techniques to control yellow starthistle, a prolific weed now infesting between 10 million and 15 million acres in California. With many options available to land managers, developing a long-term, strategic management plan most suitable to a specific area can be complicated. It requires careful consideration of the advantages and disadvantages of each option and how best to incorporate appropriate ones into an effective program. Management strategies include timely mowings, grazing, clover plantings, biological control insects, prescribed burning and selective applications of herbicides. In addition to new developments in the management of yellow starthistle, public awareness of invasive weed issues has translated into major legislative changes that should encourage and assist private and public landowners and managers to initiate long-term programs to prevent and manage invasive weeds, particularly yellow starthistle.
Interplanting grasses into alfalfa controls weeds in older stands
by Timothy S. Prather, W. Thomas Lanini, Steve Orloff, Ronald Vargas, Jerry L. Schmierer, W. Mick Canevari, Shannon Mueller, Warren Bendixen, Rose L. Krebill-Prather
| Full text HTML  | PDF  
Planting grasses into older alfalfa stands reduces weeds and suppresses alfalfa weevil populations.
Interplanting grasses into alfalfa effectively uses grass competition to reduce the amount of weeds in alfalfa hay. The increased production offsets a lower price for the hay content, making the alfalfa-grass hay equally profitable to alfalfa hay sprayed with herbicide. This technique avoids plant-back restrictions from use of some herbicides. Alfalfa weevil populations can be reduced below threshold levels, providing additional benefit from the technique. The percentage of growers interplanting did not change but nearly half of the 24% of growers using interplanting are new users of the technique. Cooperative Extension was viewed as the most useful source for interplanting information by 64% of farmers surveyed.
Solarization and biofumigation help disinfest soil
by James J. Stapleton, Clyde L. Elmore, James E. DeVay
| Full text HTML  | PDF  
Soil solarization and biofumigation can help disinfest soil in certain cases when methyl bromide becomes unavailable.
Preplant soil fumigation with methyl bromide is scheduled to be phased out by 2005. Chemical and nonchemical alternatives are being researched and identified. Soil solarization and/or biofumigation can help fill the gap in certain cases. These alternative methods of soil disinfestation are also of value to organic growers, home gardeners and others who will not or cannot use the soil fumigation chemicals employed by many conventional commercial growers.
Analysis shows climate-caused decreases in Scott River fall flows
by Daniel J. Drake, Kenneth W. Tate, Harry Carlson
| Full text HTML  | PDF  
Knowing that fall flows in the Scott River are primarily climatecontrolled may be useful for making water management decisions.
Because of declining anadromous fisheries, resource managers are concerned about the timing and quantity of water flows in Northern California's Scott River. We analyzed 48 years of flow and precipitation data to improve our collective understanding of the Scott River fall flow regime and to provide information for current and future fisheries-restoration efforts. Fall flows are primarily controlled by the water content of snow and precipitation during the previous 12 months. These two factors account for nearly 80% of the variation in fall flows. Our analysis shows that downward trends in fall flows appear to be explained by a decrease in the water content of the snow falling on the Scott River watershed. This information will be useful in assessing the relative benefits of conservation and restoration strategies against the larger background of climate-caused changes in river flow.
Algal-bacterial treatment facility removes selenium from drainage water
by Nigel W.T. Quinn, Terrance Leighton, Tryg J. Lundquist, F. Bailey Green, Max A. Zárate, William J. Oswald
| Full text HTML  | PDF  
The best-performing algal-bacterial selenium removal plant reduced nitrate by more than 95% and reduced selenium by 80%.
Growers and pesticide applicators in California are legally required to file pesticide use reports with details about every application to commercial crops. We used the individual applicator records to document a decline in the use of organophosphate pesticides (OP) on almond and stone fruit orchards during the rainy season in California, a time period in which the trees are dormant. The decline is important because dormant applications are a major source of surface water contamination and the Federal Clean Water Act mandates a reduction in movement of OPs into surface water. However, the decline in use of OPs has been accompanied by an increase in use of pyrethroid pesticides, particularly in stone fruit orchards. Additional implementation of “reduced-risk” integrated pest management practices could further reduce use of dormant applications of OPs and pyrethroids on almonds and stone fruit orchards.
Nutrition lessons improve Hispanic teenage girls' knowledge
by Michelle R. Neyman, Gladys Block, Jennifer L. Morris, Sheri Zidenberg-Cherr
| Full text HTML  | PDF  
Nutrition education improved the nutrition knowledge of many girls, but had little effect on their eating habits.
Nutrition knowledge and dietary intake among Hispanic teenage girls were assessed before and after a nutrition education intervention. We found that subjects were consuming several important nutrients at levels below current government recommendations. On average, Hispanic teenage girls consumed folate, calcium, zinc and iron at levels that were 40%, 36%, 18% and 8% below current recommendations, respectively. Participation in the five-lesson nutrition education program resulted in a 50% increase in nutrition knowledge and modest changes in dietary behavior; we observed improved dietary intake of vitamin C. Long-term interventions are needed to improve dietary habits as one means of enhancing overall health.
Tuolumne County shops capture local dollars
by Joan Wright, George Goldman, Nancy Feldman, Andrew Murray
| Full text HTML  | PDF  
A survey of consumers shows that local businesses are capturing more local dollars than 8 years earlier.
Tuolumne County retail merchants think that they are not capturing the lion's share of local sales, but they are! County residents do not go out of the county to shop as much as businesses think. A survey conducted in 1997 by the UC Cooperative Extension Office in Tuolumne County surveyed shoppers and checked perceptions of local business owners. The survey found that the proportion of money that is spent out of the county is not as high as businesses surmised. This follow-up to a similar study conducted in 1989 also showed that businesses are capturing more local dollars than they were 8 years earlier.
Grading error reduces grower incentives to increase prune quality
by James A. Chalfant, Jennifer S. James, Nathalie Lavoie, Richard J. Sexton
| Full text HTML  | PDF  
Because grading error tends to reward smaller prunes, growers have less incentive to produce larger prunes.
Grading is important to ensure the production of high-quality foods, but it is usually done with error, distorting market signals and diminishing incentives to produce high-quality products. Size is the main quality criterion for dried prunes and the crucial characteristic in determining prune value. We studied the economic effects of errors in commodity grading, focusing in particular on the implications of one-way (asymmetric) grading errors, namely when small, low-quality product is erroneously classified as high quality, but not vice versa. In an application to the California prune industry, we estimated the extent to which large prunes are undervalued and small prunes are overvalued. We conclude that grading error means that prunes graded as high-quality may not really be high-quality prunes. The presence of these incorrectly graded prunes depresses the prices that growers are paid for high-quality prunes and increases the net returns for small prunes. As a result, growers face reduced incentives to produce larger prunes.

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