Progress 01/01/07 to 12/31/07
Outputs
Asian soybean rust (Phakopsora pachyrihizi) (ASR), arrived in the U.S. in 2004, continues to spread across the U.S., affecting more regions in 2007 than at any other time and has the potential for being the most important impediment to organic soybean production. As of December 2007, ASR has ranged as far north as Canada and Iowa, although the disease appeared late in the season and did not affect yields. At the initiation of this research, there no organic-compliant control of ASR. The purpose of this project is to evaluate tools, including organic-compliant fungicides and cultural strategies to limit damage. Our objectives include on-station studies and on-farm surveys conducted in Florida, where rust has been extremely active and testing organic fungicides in Iowa, Michigan and Pennsylvania for their effect on yields and other soybean diseases. Pennsylvania and Michigan missed ASR in 2007, and no ASR was found in organic soybean trials in Iowa, probably due to
exceptionally dry weather in the Southeast during the early soybean-growing season. In Florida, an organic trial was established in 2005 to examine effects of organic-compliant fungicides on ASR on soybeans grown on land in transition to certified organic status. Fungicides were tested in 2007 and plants rated according to the Horsfall-Barrett rating scale (0 = 0%; 11 = 100% diseased). Plants treated with copper hydroxide and copper sulfate exhibited the lowest rates of disease, with no differences detected between the control and Bacillus pumilis, capryllic acid, Hoshizaki water, hydrogen dioxide, and microbial combinations (AN and MAF). These results suggest promise for copper-based products for organic management of ASR, but issues associated with extended copper use must be considered. Research to date has shown that in Iowa, Pennsylvania and Michigan, no significant differences in organic soybean yields were found in soybeans treated with Bacillus pumilis, an OMRI-listed
fungicide that has shown some efficacy against ASR in South Africa. Other ASR fungicide products tested in Pennsylvania (soybean oil) caused some phytotoxicity in organic soybeans. Organic soybean yields were excellent in 2007 in Iowa and Pennsylvania with no differences between three varieties tested. Severe drought in Michigan, yields only reached 13 bu/acre. No significant differences in yields were detected when soybeans were planted earlier (May 22) versus later (June 16), a possible strategy for ASR management. No significant differences in mite or natural enemy diversity, or nematode community structure were detected among the fungicide treatment or planting dates, but the population densities of bacterivores in organic plots were generally higher than those associated with conventional soybean production sites Michigan Another potential strategy, planting soybeans into a rolled cover crop, was evaluated for yield and disease effects. In Iowa, in 2007, yields averaged 45
bu/acre in a rolled cover crop of hairy vetch/rye with no rust detected and other soybean diseases ranging from 0 to 2.3% of leaves infected.
Impacts
This research has identified potential strategies, such as copper-based fungicides, for effectively managing ASR in organic systems and mitigatingn losses in the event of severe infection. 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. Dissemination of information to over 600 people has occurred through presentations at Field Days and the Iowa Organic Conference, Michigan Sustainable Farming Association conference and the Upper Midwest Organic Farming Conference. On-line reports have been posted at the following sites: NewFarm, New Ag Network, OrganicAgInfo and each institutions' research farm and individual organic websites, including http://extension.agron.iastate.edu/organicag/. Through these efforts, 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. Activities supported through this project in 2007 included the establishment of four research experiments in Florida, Iowa, Michigan and Pennsylvania; analyzing all date from sites; four state reports and one overall project report; three Field Days in Michigan, Iowa, and Pennsylvania; the Florida site serving as a demonstration site for over 50 people who received training in ASR; and individual consulting with three organic soybean companies regarding ASR management. Products produced included new applied knowledge and technology for ASR management in organic systems, and the sharing of this information on websites listed below.
Publications
- Bird, G. W. 2007. Correction: Asian Soybean Rust not found in Michigan in 2007. The IPM Practitioner: Monitoring the Field of Pest Management 29 (7/8):9.
- Delate, K. 2007. Evaluation of Organic Soybean Rust Treatments for Organic Production Neely-Kinyon Trial. 2007. Iowa State University Experiment Station Reports, Ames, IA: http://www.ag.iastate.edu/farms/06reports/arm/EvalOrganicSoybean.pdf
- Grossman, J. 2007. ESA 2006 Annual Meeting Highlights 3rd Part: Organic Soy Fungicides. The IPM Practitioner: Monitoring the Field of Pest Management 29 (5/6):14.
- Hepperly, P. 2007. Old Asian Soybean Rust research from many places holds valuable natural defense clues. The Rodale Institute New Farm on-line journal: http://www.newfarm.org/columns/research_paul/2007/0407/soybeanrust.sh tml
- Johnson, A.m., M. E. Whalon, D. R. Norton, W. W. Byran. 2006. Effect of organic fungicides on natural enemies in Michigan soybean production. Proceedings of the 2006 Annual Meeting of the Entomological Society of America. Abstr. D 0038.
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