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Assessment of the Potential Year-Round Establishment of Soybean Rust Throughout the World

May 2004 , Volume 88 , Number  5
Pages  523 - 529

S. Pivonia and X. B. Yang , Iowa State University, Department of Plant Pathology, Ames 50011

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Accepted for publication 2 January 2004.

Soybean rust (Phakopsora pachyrhizi Sydow) has been known to occur in eastern Asia and Aus-tralia for decades. In recent years, the disease entered Africa and South America and has spread rapidly in these continents. It has become a concern to the U.S. soybean industry. To assess the threat of soybean rust, we used a modeling approach to determine the potential geographical zones where the fungus might overwinter and serve as source areas for seasonal epidemics. Long-term meteorological averages were used to assess the temperature stresses by using CLIMEX, and the dry stress with an algorithm developed in this study. Integration of stresses was used to predict the likelihood of survival of the rust in a defined location. Our results suggest that the new soybean rust invasions in Africa and South America occurred in the areas where the fungus might persist year-round. The main regions where rust has not been reported but might overwinter are located in the western hemisphere, including northern South America, Central America, the Caribbean, Mexico, southern Texas, and Florida. Southeastern China and neighboring areas are suggested as the primary regions where initial spores for soybean rust epidemics in central China are produced. If the disease is to establish in the United States, it is likely to be restricted to parts of Florida and southern Texas during the winter in the frost-free areas or areas where the fungus could overcome short periods of below-freezing temperatures. Occurrence of rust epidemics within the U.S. soybean belt would depend on south-to-north dispersal of uredospores.

Additional keyword: overwintering

© 2004 The American Phytopathological Society