Can We Simulate the Impact of Soybean Rust in the South Central Soybean Production Regions of the United States?.

Studying the impact of soybean rust (SBR) is important to determine the potential damage the disease may cause to regional soybean production. However, due to the exotic nature of the pathogen that causes SBR, federal restrictions have prohibited field inoculation in areas where the disease is not currently present. Simulating the impact of SBR in the field may be possible by mimicking the impact of SBR on soybean canopies.  The objective of the current study is to develop a method to simulate the injury caused by SBR on field grown soybean. An earlier study on the mechanism of SBR-induced yield loss, determined that: accelerated leaf drop, reduction in green leaf area, and reduction in photosynthesis of green leaf area all contributed towards yield loss. Using data from Brazil, the progressive impact of SBR on photosynthetically active leaf area was artificially simulated in soybean canopies grown in Lexington, KY and in Baton Rouge, LA. The experiment was a randomized complete block design, with four replications, and a split-plot treatment arrangement. The eight periodic biomass samplings were the main plots, and the three disease simulation treatments (disease-free, disease beginning at R2 and disease beginning at R5) were the split plots. Measurements included leaf area, plant biomass, and radiation interception. The simulation resulted in similar yield losses (relative to control) to those observed in Brazil, despite the large variation in soybean productions practices used in the two regions. This approach appears to be useful to simulate the impact of SBR on soybean yield.