Extension Responds: Soybean Rust
Soybean Rust Update – July 26, 2005
By Craig Grau , Plant Pathology, University of Wisconsin Madison/Extension
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The status of soybean rust in the southern U.S. has not changed since last week.
Active infections of soybean rust are confined to northern Florida, southern Georgia southern Alabama and southeast Mississippi. Soybean rust teams continue to scout in the Gulf region, Kentucky and Tennessee. Although soybean rust-like spores were deposited in spore traps, there is no evidence that soybean plants have been infected with the soybean rust pathogen in Tennessee and Kentucky.
UW-Madison staff members are monitoring spore traps located at the University Agricultural Research Stations at Arlington, West Madison and Lancaster. Samples from spore traps are assayed for the soybean rust pathogen by the DNA-based technology, PCR. As of July 25, the soybean rust pathogen has not been detected at these locations and symptoms of soybean rust have not been observed on plants at each monitoring site. A private laboratory in Wisconsin has analyzed samples collected from rain collection spore traps and reported a strong positive reaction for soybean rust using PCR at one sight, and weaker reactions at three other sites. Staff at the UW-Madison Plant Pathogen Detection Clinic also assayed these samples and found them to be negative for the soybean rust pathogen. Based on data generated by UW-Madison staff, the soybean rust pathogen is not present in Wisconsin.
The recent rains and lower air temperatures are providing a favorable environment for the soybean rust pathogen. However, until there is evidence of active soybean rust in southern Illinois, I believe the potential for soybean rust is exceedingly low for Wisconsin.
The following recommendations are offered for fungicides and soybean. If you were planning to apply a fungicide for soybean plant health improvement in the absence of soybean rust, now would be a good time to do so at the R2‑R4 growth stages. If you were not planning to apply a fungicide for general plant health improvement, but would consider a fungicide for rust control, current data from the UW indicates there is not a need to apply fungicides for control of soybean rust.
Monitor the USDA Soybean Rust Website for the latest on movement of soybean rust. Consult the Wisconsin Soybean Health website for the Wisconsin perspective on soybean rust. Consult the toll free voice message from the UW Plant Disease Detection Clinic at 1-866-787-8411.
Contact: Craig Grau, 608-262-6289, cg6@plantpath.wisc.edu