Soybean Rust

The potential outbreak of Asian soybean rust or other devastating crop pathogens, either as an act of biowarfare or natural outbreaks is threat to food production and security in the U.S. and around the world. Asian soybean rust is a fungal pathogen that can cause significant yield loss in soybean. In areas where the pathogen is common, yield losses of up to 80% have been reported.

Asian soybean rust [Phakopsora pachyrhizi (Syd. & P. Syd.)] is a fungal pathogen that can cause significant yield loss in soybeans [Glycine Max (L.)]. In areas where rust is common, yield losses up to 80% have been reported (Hsu and Wu, 1968). The USDA (2002) reported yield losses in South America and Africa ranging from 10 to 60 percent. A past economic risk analysis projected that the potential losses in the U.S. would be $7.1 billion per year, once soybean rust was established (Kuchler et al., 1984). A conservative prediction indicated yield losses greater than 10% in nearly all the U.S. soybean growing areas with losses up to 50% in the Mississippi delta and southeastern coastal states (Yang, 1995).

Late in the 2004 growing season, soybean rust was discovered in the continental U.S. near Baton Rouge, Louisiana. Prior to that, soybean rust had been found in Hawaii (Killgore and Heu, 1994) as well as the continents of Africa, Asia, Australia, and South America (NCPMC, 2003; USDA, 2002). Scouting efforts led by USDA and state extension staff later revealed the pathogen was present in isolated locations throughout the Mississippi Delta and Gulf Coast states (Figure 1).

Figure 1. Locations where soybean rust was confirmed late in the 2004 growing season.

When this particular study was initiated, SBR had not yet been found in the U.S. SBR, however, was found in the U.S. during the 2004 and 2005 growing seasons, but the spatial extent of infection remained isolated. Thus, a cooperative agreement was established with EMBRAPA (the Brazilian Agricultural Research Corporation) to assist ITD in obtaining ground data in Brazil. Staff from ITD traveled to Brazil at the end of January 2005 to collect ground data near the city of Campo Novo do Parecis in the Mato Grosso state (Figure 2). Approximately 370,000 ha of soybean are grown in the area around Campo Novo do Parecis.

Figure 2. Location of the study area in Brazil. Ground data was collected near the city of Campo Novo do Parecis.

Temporal vegetation index products derived from MODIS were successfully used to develop a soybean crop-type classification for the study area. However, detection of the rust pathogen was difficult using available Earth science data, and suitable results were not obtained. None-the-less, the results of this evaluation demonstrate that NASA Earth science data could make important contributions to surveillance programs targeting crop and food security.

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