Soybean Rust: A New Pest of Soybean Production

NON-TECHNICAL SUMMARY: Soybean rust, a serious problem in other parts of the world, is now in South America and posses a serious threat to soybean production in the US. This project will prepare U.S. soybean growers for rust by providing the means for early, accurate detection of the disease and give tested control strategies that growers can use once the disease is here. These control strategies will include both cultivar resistance and chemical control.

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APPROACH: Survey procedures will be developed based on both field scouting and remote senesing to detect soybean rust. Educational materials will be developed that will show rust symptoms on soybean and on other hosts. These will be made available to county agents, consultants and growers. The impact of soybean rust will be evaluated in cultivar and fungucide tests here and in South America to determine the effect of cultivar resistance/tolerance and fungicides on the development of rust and on yield loss. Various control strategies will be evaluated. These will include evaluating the timing and efficacy of various fungicides, evaluating cultivar resistance/tolerance, determining when to apply fungicides based on disease pressure and environmental conditions. These results will be summarized in extension and research publications and presented at grower meetings. Results from experiments and grower experiences will be used to determine new research approaches that could increase control.
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PROGRESS: 2003/01 TO 2005/09<BR>
Soybean rust activities this year have involved spore trapping, fungicide tests, helping organize state and national meetings, and presentations at state, national and international meetings. The spore trapping project was done in cooperation with Syngenta. Syngenta worked with researchers in 13 states who maintained spore traps during the growing season. These researchers sent slides from the spore traps to me weekly for evaluation. I had two technicians examine the slide under a microscope and determine if soybean rust-like spores were present. We received 1,263 slides from 96 spore traps in 13 states. We found soybean rust-like spores at least once from each state and on a total of 201 slides. Soybean rust only developed in five states and the diseased progressed significantly only in Georgia and Alabama. In Georgia and Alabama, we found soybean rust-like spores 5 to 77 days before they found soybean rust in the adjacent soybean fields, on average 30 days before rust was found. However, at one site in Georgia, we found soybean rust-like spores 30 days after they found rust in the plot. At one location in Mississippi, they found rust and destroyed the plot with 48 hours, but we had not found soybean rust-like spores in that trap. Several fungicide tests were conducted for soybean rust. Because the weather was very hot and very dry, there was no soybean rust in these tests or in Arkansas and very little foliar disease on soybean of any kind. Even in the absence of foliar disease, applications of azoxystrobin or pyraclostrobin increased yields over the control. Besides research, I gave soybean rust presentations at local grower meetings, helped arrange the National Symposium on Soybean Rust and spoke there and also presented a soybean rust talk in Argentina at the Pan American Soybean Rust Conference.

<BR> <BR> IMPACT: 2003/01 TO 2005/09 <BR>
The spore trap project revealed that spores of the soybean rust pathogen could be trapped before disease developed and that the fungus was very widely spread last year even though the disease was not. Presentations and organization of meetings helped to inform the scientific community and the public about soybean rust.