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California Agriculture, Vol. 67, No.3

Special issue: Methyl bromide alternatives
Cover:  Growers have long used methyl bromide to essentially sterilize soil, but this fumigant is being phased out due to environmental and health concerns. New research helps identify methyl bromide alternatives to control pathogens, pests and weeds in strawberries (p 139), almonds and stone fruits (p 128), forest nurseries (p 153) and perennial nursery crop stock (p 181), and shows that multi-layer tarps reduce fumigant emissions (p 147). This work is part of the Pacific-Area Wide Integrated Methyl Bromide Alternatives Program, a USDA-funded collaboration of UC and USDA researchers. Shown is a strawberry field in coastal southern California, a region where fumigants are restricted to protect people’s health. Photo by Janet Hudson
July-September 2013
Volume 67, Number 3

Peer-reviewed research and review articles

Managing the almond and stone fruit replant disease complex with less soil fumigant
by Greg T. Browne, Bruce D. Lampinen, Brent A. Holtz, David A. Doll, Shrinivasa K. Upadhyaya, Leigh S. Schmidt, Ravindra G. Bhat, Vasu Udompetaikul, Robert W. Coates, Bradley D. Hanson, Karen M. Klonsky, Suduan Gao, Dong Wang, Matt Gillis, James S. Gerik, R. Scott Johnson
| Full text HTML  | PDF  
Almond and stone fruit replant trials show that integrated management can improve crop returns and reduce the need for soil fumigation.
As much as one-third of California's almond and stone fruit acreage is infested with potentially debilitating plant parasitic nematodes, and even more of the land is impacted by Prunus replant disease (PRD), a poorly understood soilborne disease complex that suppresses early growth and cumulative yield in replanted almond and peach orchards. Preplant soil fumigation has controlled these key replant problems, but the traditional fumigant of choice, methyl bromide, has been phased out, and other soil fumigants are increasingly regulated and expensive. We tested fumigant and nonfumigant alternatives to methyl bromide in multiple-year replant trials. Costs and benefits were evaluated for alternative fumigants applied by shanks in conventional strip and full-coverage treatments and applied by shanks or drip in novel spot treatments that targeted tree planting sites. Short-term sudangrass rotation and prudent rootstock selection were examined as nonfumigant approaches to managing PRD. Trial results indicated that integrations of the treatments may acceptably control PRD with relatively little soil fumigant.
TIF film, substrates and nonfumigant soil disinfestation maintain fruit yields
by Steven A. Fennimore, Raquel Serohijos, Jayesh B. Samtani, Husein A. Ajwa, Krishna V. Subbarao, Frank N. Martin, Oleg Daugovish, Dan Legard, Greg T. Browne, Joji Muramoto, Carol Shennan, Karen Klonsky
| Full text HTML  | PDF  
Fruit yields in the steam treatments and the anaerobic soil disinfestation treatments were comparable to the Pic-Clor 60 application.
A 5-year project to facilitate the adoption of strawberry production systems that do not use methyl bromide initially focused on fumigant alternatives and resulted in increased use of barrier films that reduce fumigant emissions. The focus shifted in year 3 to evaluating and demonstrating nonfumigant alternatives: soilless production, biofumigation, anaerobic soil disinfestation (ASD) and disinfestation with steam. In the 2010–2011 strawberry production season, fruit yields on substrates were comparable to fruit yields using conventional methods. Anaerobic soil disinfestation and steam disinfestation also resulted in fruit yields that were comparable to those produced using conventionally fumigated soils. Additional work is in progress to evaluate their efficacy in larger-scale production systems in different strawberry production districts in California.
Fumigant emission reductions with TIF warrant regulatory changes
by Husein Ajwa, Michael S. Stanghellini, Suduan Gao, David A. Sullivan, Afiqur Khan, William Ntow, Ruijun Qin
| Full text HTML  | PDF  
Increasing the standard tarping period from 5 days to 10 days reduced peak and total emissions significantly in a 2011 trial.
With methyl bromide's phase-out, most growers have turned to alternative fumigants, particularly 1,3-dichloropropene (1,3-D) and chloropicrin. These alternatives are tightly regulated because they are classified as toxic air contaminants and volatile organic compounds; the latter combine with other substances to produce ground-level ozone (smog). Two ambient air monitoring studies were conducted to evaluate the potential of totally impermeable film (TIF) to reduce emissions from shank applications of chloropicrin and 1,3-D. In 2009, a study demonstrated that TIF reduced chloropicrin and 1,3-D peak emissions by 45% and 38%, respectively, but TIF did not reduce total emissions when it was cut after 6 days. In 2011, increasing the tarp period from 5 to 10 days decreased chloropicrin and 1,3-D peak emissions by 88% and 78%, and their total emissions by 64% and 43%, respectively. Concurrent dynamic flux chamber results corroborated the ambient air monitoring data. These studies provide regulatory agencies with mitigation measures that should allow continued fumigant use at efficacious application rates.
Forest nurseries face critical choices with the loss of methyl bromide fumigation
by Jerry E. Weiland, Will R. Littke, Diane L. Haase
| Full text HTML  | PDF  
Integrated pest management approaches can help compensate for the loss of methyl bromide, but converting to container production may be the best option.
Forest nurseries in the western United States have relied for decades on methyl bromide to control soilborne pests. Numerous studies have investigated alternative fumigants, alternative application methods and nonfumigant approaches for their ability to reduce soilborne pest populations and produce quality, disease-free seedlings. We review the recent studies and identify where research is needed to assist the industry's transition away from methyl bromide. For the immediate, foreseeable future, an integrated approach combining nonfumigant and fumigant methods will provide the best strategy. Nevertheless, the industry may need to transition completely to container production if fumigant regulations become more restrictive.
Monitoring soil carbon will prepare growers for a carbon trading system
by Emma C. Suddick, Moffatt K. Ngugi, Keith Paustian, Johan Six
| Full text HTML  | PDF  
Baseline estimates are the first step in establishing a long-term soil carbon monitoring network for Northern California perennial croplands.
California growers could reap financial benefits from the low-carbon economy and cap-and-trade system envisioned by the state's AB 32 law, which seeks to lower greenhouse gas emissions statewide. Growers could gain carbon credits by reducing greenhouse gas emissions and sequestering carbon through reduced tillage and increased biomass residue incorporation. First, however, baseline stocks of soil carbon need to be assessed for various cropping systems and management practices. We designed and set up a pilot soil carbon and land-use monitoring network at several perennial cropping systems in Northern California. We compared soil carbon content in two vineyards and two orchards (walnut and almond), looking at conventional and conservation management practices, as well as in native grassland and oak woodland. We then calculated baseline estimates of the total carbon in almond, wine grape and walnut acreages statewide. The organic walnut orchard had the highest total soil carbon, and no-till vineyards had 27% more carbon in the surface soil than tilled vineyards. We estimated wine grape vineyards are storing significantly more soil carbon per acre than almond and walnut orchards. The data can be used to provide accurate information about soil carbon stocks in perennial cropping systems for a future carbon trading system.
Researchers combat resurgence of bed bug in behavioral studies and monitor trials
by Vernard R. Lewis, Sara E. Moore, Robin L. Tabuchi, Andrew M. Sutherland, Dong-Hwan Choe, Neil D. Tsutsui
| Full text HTML  | PDF  
The bed bug, until recently considered a minor problem, has lately emerged as a serious worldwide pest and a new focus for pest control research.
The worldwide resurgence of bed bugs has recently created urban pest challenges in California. Regardless of information source — newspaper, Internet, television, university or government — the message is the same: bed bugs are back, and with a vengeance. Until recently, the pest's longstanding rarity and a historical reliance on pesticide-based management have not encouraged research and public education to develop and make available current information on bed bug biology, detection and control. UC is currently directing comprehensive, collaborative programs of research and education to combat this emerging nuisance and public health threat. Laboratory and field tests were conducted by UC researchers on several commercial bed bug monitors and confirm that additional research is needed to improve the performance of existing monitors and to develop new ones.

E-Edition

Preplant 1,3-D treatments test well for perennial crop nurseries, but challenges remain
by Bradley D. Hanson, Suduan Gao, James Gerik, Ruijun Qin, J. Alfonso Cabrera, Amit J. Jhala, M. Joy M. Abit, David Cox, Brian Correiar, Dong Wang, Gregory T. Browne
| Full text HTML  | PDF  
Growers' ability to produce clean planting stock without methyl bromide could impact the nursery, orchard, vineyard and ornamental industries
Preplant fumigation with methyl bromide commonly is used in open-field perennial crop nurseries in California for control of plant-parasitic nematodes, pathogens and weeds. Because this fumigant is being phased out, alternatives are needed to ensure the productivity of the perennial crop nursery industry as well as the ornamental, orchard and vineyard production systems that depend on clean planting stock. As part of the USDA Area-Wide Pest Management Program for Integrated Methyl Bromide Alternatives, several perennial crop nursery projects were conducted in California from 2007 to 2011 to test and demonstrate registered alternative fumigants and application techniques that maximize performance and minimize environmental impacts. The project was designed to evaluate shank application and soil surface sealing methods intended to reduce aboveground emission and improve soil performance of 1,3-dichloropropene, a leading methyl bromide alternative for nurseries. In these garden rose and tree nursery experiments, 1,3-dichloropropene treatments performed well regardless of application techniques. In this article, we highlight recent research and discuss the significance and remaining challenges for adoption of methyl bromide alternatives in this unique nursery stock production system.
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California Agriculture, Vol. 67, No.3

Special issue: Methyl bromide alternatives
Cover:  Growers have long used methyl bromide to essentially sterilize soil, but this fumigant is being phased out due to environmental and health concerns. New research helps identify methyl bromide alternatives to control pathogens, pests and weeds in strawberries (p 139), almonds and stone fruits (p 128), forest nurseries (p 153) and perennial nursery crop stock (p 181), and shows that multi-layer tarps reduce fumigant emissions (p 147). This work is part of the Pacific-Area Wide Integrated Methyl Bromide Alternatives Program, a USDA-funded collaboration of UC and USDA researchers. Shown is a strawberry field in coastal southern California, a region where fumigants are restricted to protect people’s health. Photo by Janet Hudson
July-September 2013
Volume 67, Number 3

Peer-reviewed research and review articles

Managing the almond and stone fruit replant disease complex with less soil fumigant
by Greg T. Browne, Bruce D. Lampinen, Brent A. Holtz, David A. Doll, Shrinivasa K. Upadhyaya, Leigh S. Schmidt, Ravindra G. Bhat, Vasu Udompetaikul, Robert W. Coates, Bradley D. Hanson, Karen M. Klonsky, Suduan Gao, Dong Wang, Matt Gillis, James S. Gerik, R. Scott Johnson
| Full text HTML  | PDF  
Almond and stone fruit replant trials show that integrated management can improve crop returns and reduce the need for soil fumigation.
As much as one-third of California's almond and stone fruit acreage is infested with potentially debilitating plant parasitic nematodes, and even more of the land is impacted by Prunus replant disease (PRD), a poorly understood soilborne disease complex that suppresses early growth and cumulative yield in replanted almond and peach orchards. Preplant soil fumigation has controlled these key replant problems, but the traditional fumigant of choice, methyl bromide, has been phased out, and other soil fumigants are increasingly regulated and expensive. We tested fumigant and nonfumigant alternatives to methyl bromide in multiple-year replant trials. Costs and benefits were evaluated for alternative fumigants applied by shanks in conventional strip and full-coverage treatments and applied by shanks or drip in novel spot treatments that targeted tree planting sites. Short-term sudangrass rotation and prudent rootstock selection were examined as nonfumigant approaches to managing PRD. Trial results indicated that integrations of the treatments may acceptably control PRD with relatively little soil fumigant.
TIF film, substrates and nonfumigant soil disinfestation maintain fruit yields
by Steven A. Fennimore, Raquel Serohijos, Jayesh B. Samtani, Husein A. Ajwa, Krishna V. Subbarao, Frank N. Martin, Oleg Daugovish, Dan Legard, Greg T. Browne, Joji Muramoto, Carol Shennan, Karen Klonsky
| Full text HTML  | PDF  
Fruit yields in the steam treatments and the anaerobic soil disinfestation treatments were comparable to the Pic-Clor 60 application.
A 5-year project to facilitate the adoption of strawberry production systems that do not use methyl bromide initially focused on fumigant alternatives and resulted in increased use of barrier films that reduce fumigant emissions. The focus shifted in year 3 to evaluating and demonstrating nonfumigant alternatives: soilless production, biofumigation, anaerobic soil disinfestation (ASD) and disinfestation with steam. In the 2010–2011 strawberry production season, fruit yields on substrates were comparable to fruit yields using conventional methods. Anaerobic soil disinfestation and steam disinfestation also resulted in fruit yields that were comparable to those produced using conventionally fumigated soils. Additional work is in progress to evaluate their efficacy in larger-scale production systems in different strawberry production districts in California.
Fumigant emission reductions with TIF warrant regulatory changes
by Husein Ajwa, Michael S. Stanghellini, Suduan Gao, David A. Sullivan, Afiqur Khan, William Ntow, Ruijun Qin
| Full text HTML  | PDF  
Increasing the standard tarping period from 5 days to 10 days reduced peak and total emissions significantly in a 2011 trial.
With methyl bromide's phase-out, most growers have turned to alternative fumigants, particularly 1,3-dichloropropene (1,3-D) and chloropicrin. These alternatives are tightly regulated because they are classified as toxic air contaminants and volatile organic compounds; the latter combine with other substances to produce ground-level ozone (smog). Two ambient air monitoring studies were conducted to evaluate the potential of totally impermeable film (TIF) to reduce emissions from shank applications of chloropicrin and 1,3-D. In 2009, a study demonstrated that TIF reduced chloropicrin and 1,3-D peak emissions by 45% and 38%, respectively, but TIF did not reduce total emissions when it was cut after 6 days. In 2011, increasing the tarp period from 5 to 10 days decreased chloropicrin and 1,3-D peak emissions by 88% and 78%, and their total emissions by 64% and 43%, respectively. Concurrent dynamic flux chamber results corroborated the ambient air monitoring data. These studies provide regulatory agencies with mitigation measures that should allow continued fumigant use at efficacious application rates.
Forest nurseries face critical choices with the loss of methyl bromide fumigation
by Jerry E. Weiland, Will R. Littke, Diane L. Haase
| Full text HTML  | PDF  
Integrated pest management approaches can help compensate for the loss of methyl bromide, but converting to container production may be the best option.
Forest nurseries in the western United States have relied for decades on methyl bromide to control soilborne pests. Numerous studies have investigated alternative fumigants, alternative application methods and nonfumigant approaches for their ability to reduce soilborne pest populations and produce quality, disease-free seedlings. We review the recent studies and identify where research is needed to assist the industry's transition away from methyl bromide. For the immediate, foreseeable future, an integrated approach combining nonfumigant and fumigant methods will provide the best strategy. Nevertheless, the industry may need to transition completely to container production if fumigant regulations become more restrictive.
Monitoring soil carbon will prepare growers for a carbon trading system
by Emma C. Suddick, Moffatt K. Ngugi, Keith Paustian, Johan Six
| Full text HTML  | PDF  
Baseline estimates are the first step in establishing a long-term soil carbon monitoring network for Northern California perennial croplands.
California growers could reap financial benefits from the low-carbon economy and cap-and-trade system envisioned by the state's AB 32 law, which seeks to lower greenhouse gas emissions statewide. Growers could gain carbon credits by reducing greenhouse gas emissions and sequestering carbon through reduced tillage and increased biomass residue incorporation. First, however, baseline stocks of soil carbon need to be assessed for various cropping systems and management practices. We designed and set up a pilot soil carbon and land-use monitoring network at several perennial cropping systems in Northern California. We compared soil carbon content in two vineyards and two orchards (walnut and almond), looking at conventional and conservation management practices, as well as in native grassland and oak woodland. We then calculated baseline estimates of the total carbon in almond, wine grape and walnut acreages statewide. The organic walnut orchard had the highest total soil carbon, and no-till vineyards had 27% more carbon in the surface soil than tilled vineyards. We estimated wine grape vineyards are storing significantly more soil carbon per acre than almond and walnut orchards. The data can be used to provide accurate information about soil carbon stocks in perennial cropping systems for a future carbon trading system.
Researchers combat resurgence of bed bug in behavioral studies and monitor trials
by Vernard R. Lewis, Sara E. Moore, Robin L. Tabuchi, Andrew M. Sutherland, Dong-Hwan Choe, Neil D. Tsutsui
| Full text HTML  | PDF  
The bed bug, until recently considered a minor problem, has lately emerged as a serious worldwide pest and a new focus for pest control research.
The worldwide resurgence of bed bugs has recently created urban pest challenges in California. Regardless of information source — newspaper, Internet, television, university or government — the message is the same: bed bugs are back, and with a vengeance. Until recently, the pest's longstanding rarity and a historical reliance on pesticide-based management have not encouraged research and public education to develop and make available current information on bed bug biology, detection and control. UC is currently directing comprehensive, collaborative programs of research and education to combat this emerging nuisance and public health threat. Laboratory and field tests were conducted by UC researchers on several commercial bed bug monitors and confirm that additional research is needed to improve the performance of existing monitors and to develop new ones.

E-Edition

Preplant 1,3-D treatments test well for perennial crop nurseries, but challenges remain
by Bradley D. Hanson, Suduan Gao, James Gerik, Ruijun Qin, J. Alfonso Cabrera, Amit J. Jhala, M. Joy M. Abit, David Cox, Brian Correiar, Dong Wang, Gregory T. Browne
| Full text HTML  | PDF  
Growers' ability to produce clean planting stock without methyl bromide could impact the nursery, orchard, vineyard and ornamental industries
Preplant fumigation with methyl bromide commonly is used in open-field perennial crop nurseries in California for control of plant-parasitic nematodes, pathogens and weeds. Because this fumigant is being phased out, alternatives are needed to ensure the productivity of the perennial crop nursery industry as well as the ornamental, orchard and vineyard production systems that depend on clean planting stock. As part of the USDA Area-Wide Pest Management Program for Integrated Methyl Bromide Alternatives, several perennial crop nursery projects were conducted in California from 2007 to 2011 to test and demonstrate registered alternative fumigants and application techniques that maximize performance and minimize environmental impacts. The project was designed to evaluate shank application and soil surface sealing methods intended to reduce aboveground emission and improve soil performance of 1,3-dichloropropene, a leading methyl bromide alternative for nurseries. In these garden rose and tree nursery experiments, 1,3-dichloropropene treatments performed well regardless of application techniques. In this article, we highlight recent research and discuss the significance and remaining challenges for adoption of methyl bromide alternatives in this unique nursery stock production system.

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