Progress 07/15/05 to 07/14/07
Outputs
Asian soybean rust (Phakopsora pachyrihizi) (ASR), which arrived in the U.S. in 2004, was described as having the potential to be the single most important impediment to organic soybean production in the U.S. Asian soybean rust has ranged as far north as Indiana and Illinois, with an anomalous find in Iowa. The Organic Soybean Rust Management Initiative was established to investigate the potential for organic-compliant fungicides and other strategies for organic soybean producers in managing ASR. The project supported the establishment of a network of organic soybean researchers at Iowa State University, the University of Florida, Michigan State University and The Rodale Institute who examined tactics for ASR (at the University of Florida) and other soybean diseases affecting organic soybeans. At the initiation of this research, there were no known organic-compliant controls of ASR, but we have successfully identified several products showing efficacy against ASR in
Florida. The Upper Midwest and Pennsylvania missed ASR in 2006 and 2007, probably due to dry weather in the Southeast, particularly in east Texas, during the early soybean-growing season. The trial at the University of Florida North Florida Research and Education Center in Quincy, Florida, was established in 2005 to examine effects of organic-compliant fungicides on ASR on soybeans grown on land in transition to certified organic status. The materials tested were: 1. Champion(R) Wettable Powder (Nufarm, Burr Ridge, Illinois) containing 77% copper hydroxide 2. Ballad(R) (AgraQuest, Davis, California) containing 1.38% Bacillus pumilus 3. Electrified Water 4. OxiDate(R) (BioSafe, East Hartford, Connecticut) 5. Agricoat Natural II(R) (Agricoat LLC, Soledad, California) 6. Basic Copper Sulfate 7. Micro AF (Terra Max, Minnesota) 8. Caprylic Acid (2006 and 2007) In 2005, the first year of the project, robust soybean plots and significant ASR infection were very difficult to achieve due to
drought, high soil temperatures, significant insect pests and poor germination. Because the rust appeared so late in the growing season, in mid-October, well after the critical flowering stage, no reliable data on ASR control were generated. While the drought continued to be a factor in establishing the soybean crop and ASR in 2006, a useful baseline database on material efficacy was obtained. A successful stand of organic soybeans were established and successfully inoculated with ASR. Response was relatively poor from six treatments, averaging 12 to 25% damaged leaves, compared to a 50 to 75% damage rating in control plots, except those that were sprayed with copper-based Champion WP and basic copper sulfate, which exhibited 3% damage or less. Similarly, yields in the copper treatments were superior to the other treatments, averaging 35 bushels/acre compared to 24 bushels/acre in the control plots. The question of copper build-up and eventual toxicity remains an issue. On-going
on-station and on-farm sentinel plots and surveys established in Florida, Iowa, Michigan and Pennsylvania serve as first detection sites for ASR.
Impacts
With the potential economic impact of ASR in organic systems ranging from $30 to $120 million in yield loss, a network of researchers and producers was established through the Organic Soybean Rust Management Initiative to monitor ASR spread into organic soybean producing areas and provide research results to producers throughout the U.S. Research has begun to identify potential strategies, such as copper-based fungicides for reducing loss in organic systems in the event of soybean rust. Estimated savings from organic-compliant fungicides in the southeast region could reach $1 M if organic soybean producers in that area chose to treat crops. In areas where ASR has not yet arrived, methods of improving organic soybean systems, including reduced tillage and varietal selection for other soybean diseases can result in greater maintenance of soil quality and higher returns for farmers. Through the New Farm, New Ag Network, OrganicAgInfo and each institutions' organic
websites, we have increased the knowledge base and skills of thousands of organic farmers across the U.S. in Asian soybean rust diagnostic and management tools.
Publications
- Delate, K. 2005. Researchers responding to discovery of soybean rust in the U.S. The Rodale Institute, Kutztown, PA. Available at: http://www.newfarm.org/columns/org_news/nov/rust.shtml.
- Hepperley, P. 2006. New hope for organic management of Asian rust in soybeans. The Rodale Institute, Kutztown, PA. Available at: http://www.newfarm.org/columns/research_paul/2006/0706/soybeanrust. shtml.
- Whalon, M., Bird, G., and D. Mutch. 2007. Soybean rust management articles for organic producers. www.ipm.msu.edu/soybean/rust.htm; www.ipm.msu.edu/new-ag/calendar.htm; www.new-ag.msu.edu/msurust.htm.
- Delate, K. 2007. Update on organic management of Asian soybean rust. Iowa State University Organic Ag Website, Iowa State University, Ames, IA. Available at: http://extension.agron.iastate.edu/organicag/
- Delate, K. 2006. Soybean rust management for organic farmers. Iowa State University Organic Ag Website, Iowa State University, Ames, IA. Available at: http://extension.agron.iastate.edu/organicag/info/soybeanrustjune06.p df.
- Delate, K. 2005. Iowa State University studying soybean rust in organic production. The Organic Broadcaster 13(3):10.
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Progress 07/15/05 to 07/14/06
Outputs
The Upper Midwest missed Asian Soybean Rust (ASR) in 2005 when the disease was confirmed from Florida to Missouri. As of July 25, 2006, a total of 25 counties have reported rust this year and include five in Alabama, 12 in Florida, five in Georgia, two in Louisiana, and one in Texas. However, ASR has been found on soybeans in only four counties in Alabama (1), Florida (1) and Georgia (2) with the balance found on kudzu. Despite the presence of ASR innoculum it is thought that Midwest production of soybeans will not likely be economically affected this year primarily due to dry weather prevailing in the South and Midwest. In 2005, the Organic Soybean Rust Management Initiative funded efforts to find effective control strategies for ASR and other adjunct diseases. The collaborative effort between Iowa State University and the University of Florida includes testing a suite of materials approved for organic production that may have some efficacy against ASR and/or benefit
organic soybean producers, such as providing an increased yield. In tests conducted in 2005 in Iowa, no significant difference in yield was found in non-infected soybeans treated with Ballad, an OMRI-listed fungicide that, according to the manufacturer, has shown some efficacy against ASR in South Africa. Our 2005 results from the University of Florida, where there was a sufficient incidence of ASR includes work done by Drs. David Wright and Jim Marois where they compared the incidence and severity of ASR after fungicide applications. In the first trial, Wright and Marois found that the Oxywater reduced the incidence of ASR by 45%, but the level of ASR at the end of the trial was 32.5% versus 77.5% in the control. In the second trial, Ballad at 1 quart/acre reduced ASR incidence by 65%, but again, the final level at the end of the experiment was a 32.5% ASR incidence rating in the Ballad plots compared to the control at 97.5%. The severity of ASR was reduced from 6.85 in the control
plots (on a scale of 1 to 8 where 1 is the lowest level of severity and 8 is the highest level of severity) to 4.90 in the Ballad plots. Increasing the Ballad application rate to 2 quarts/acre did not lead to an increased amount of protection.
Impacts
Early results from Ballad applications against ASR show some promise; however, to date, there remains no fungicides that can be used by certified organic soybean producers that provide the level of control available to conventional producers. We are continuing to test materials across the country in 2006 to determine potential alternatives for producers. These alternatives include other organic fungicides and early planting of soybeans to escape disease severity.
Publications
- Delate, K. and R. Turnbull June 26, 2006 http://extension.agron.iastate.edu/organicag/info/soybeanrustjune06.p df
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