Submitted to: Integrated Pest Management Reviews
Publication Type: Other
Publication Acceptance Date: 12/19/2004
Publication Date: 12/21/2004
Citation: Miles, M.R., Levy, C., Hartman, G.L. 2004. Summary of The USDA Fungicide Efficacy Trials To Control Soybean Rust In Zimbabwe 2003-2004. Integrated Pest Management Reviews. Available: http://www.ipmcenters.org/NewsAlerts/soybeanrust/
Technical Abstract: The rapid spread of Phakopsora pachyrhizi, the causal agent of Asian soybean rust, in less than a decade into Southern Africa and South America and its potential for severe yield losses make soybean rust the most destructive foliar disease of soybean. Yield losses of 30% to 60% have been reported in areas of Southern Africa and South America, with losses of 100% reported from individual fields. This disease could have a major impact on soybean production in the continental U.S. Fungicides, although not commonly used on soybean in the U.S., will be the primary tool available to manage soybean rust. The objective of these trials was to evaluate soybean rust control and yield benefits from fungicides that are or could be registered for use in the continental U.S, including those listed in the Section 18 Emergency Exemption requests submitted to the EPA. Fungicide efficacy trials were located in the central soybean production area near Harare, Zimbabwe, during the 2003-2004 growing season. A total of 46 fungicide treatments were evaluated. The majority of the plots received either two or three fungicide applications, but there were single application treatments as well. All compounds controlled soybean rust when compared to the untreated control; disease severity was less in all the plots treated with fungicides. Yield increases were also seen with each of the fungicides in the Section 18 Emergency Exemption request. The epidemic in Zimbabwe did not start until growth stage R5, as pods were being filled. The results of the efficacy trials reflect this, with significantly more severe soybean rust and greater yield losses in treatments with two applications than in those with three applications of the same product. The third application provided protection in the late season epidemic.