The Organic Soybean Rust Management Initiative

NON-TECHNICAL SUMMARY: Soybean rust (Phakopsora pachyrhizi) is a very important exotic disease threatening commercial soybean production in the U.S. In addition, there are approximately 30 other leguminous host plants, including snap beans, which are another important organic crop. Extensive surveys of soybean and various legume hosts for Asian soybean rust will be carried out in Iowa and other states in 2005. Environmental conditions in parts of the U.S. are expected to be very favorable for rust development. There is the potential that the disease, once introduced into the U.S., would likely spread throughout the main U.S. soybean production area in one season. For northern states, the level of disease in a season depends on when spores blow in from south, just like corn rust. The goal of this project is to help determine the best management practices for soybean rust in organic systems through interdisciplinary systems research and outreach with universities and NGOs in order to increase whole-farm efficiency, reduce economic risk, and enhance profitability in organic production.

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APPROACH: Biological or botanical substances included on the National List of natural and synthetic substances allowed for use in organic crop production will be applied to prevent, suppress, or control soybean rust in trials established at the University of Florida where rust was discovered in 2004. Materials to be tested will include copper hydroxide (Champion), hydrogen peroxide (Oxidate), potassium bicarbonate (Kaligreen), and biological controls (e.g., Bacillus pumilis [Ballad]). Label rates and application periods will be followed for all products. In the event of experimental materials, we will follow company recommendations. All materials are acceptable to the Organic Materials Review Institute (OMRI) and USDA-NOP. An extract from St. Johns Wort (Hypericum perforatum) (hypericin) has been reported to mitigate disease and we have been requested to include this extract in our trials, but clearance with NOP will be sought before official inclusion of unregistered materials.
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PROGRESS: 2005/07 TO 2007/07 <BR>
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.
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IMPACT: 2005/07 TO 2007/07<BR><BR>
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.