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Poster Presentations

Field surveys to monitor soybean rust in Paraguay, 2001 to 2005.

Presenter: Wilfrido Morel, Centro Regional de Investigacin Agrcola (CRIA), Paraguay
Coauthor(s): M. R. Miles2, G. L. Hartman2,3, R. D. Frederick4, T. A. Steinlage3, L. E. Cubilla5. 2USDA-ARS, Urbana, IL, 3University of Illinois, Urbana, IL, 4Foreign Disease-Weed Science Research Unit, USDA-ARS-NA, 5CAPECO, Paraguay

The first detection of soybean rust (Phakopsora pachyrhizi) in South America was in the Pirap District of Paraguay during 2001. Field surveys were established to monitor soybean rust and to identify potential over wintering sources. During the 2001-2002 and the 2002-2003 seasons, soybean rust severities were low in the main soybean production areas that were planted October through November; however, rust severity in soybean planted after mid-December was severe with yield losses up to 50%. During 2003-2004, rust was detected 25 days after soybean emergence near infected kudzu (Pueraria lobata). As in previous years, late-planted soybean had more severe soybean rust with yield losses of up to 70%. During the 2004-2005 growing season, soybean rust was severe only in northern Paraguay; other regions had a prolonged drought. In Paraguay, frequent rains and low temperatures in November and December favored early disease development in the main production, but dry conditions in January and February reduced final disease severity. Soybeans planted after mid-December had more severe soybean rust with the greatest yield losses. In each of the years, volunteer soybean and kudzu were found to be sources of over wintering the soybean rust pathogen and may be primary sources of inoculum.

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