Soybean rust was identified on August 30 in a research plot in Kinston, N.C. It was a somewhat surprising occurrence since the nearest case the disease had been found until then was in the southernmost area of Georgia, hundreds of miles from North Carolina soybean fields.
In a joint press release for that afternoon, NCSU Extension soybean pathologist Steve Koenning, crop specialist Ron Heiniger and soybean specialist Jim Dunphy recommended to farmers within 100 miles of Kinston, who had soybeans that had not yet reached the R5 stage, to consider spraying a fungicide to either prevent or retard the development of rust. They preferred a triazole fungicide or a combination of a triazole with a strobilurin type rather than a strobilurin alone.
But in two subsequent reports the experts have found no additional infections of soybean rust in the state. In their Sept. 7 report, they noted they had examined approximately 900 soybean leaves in the 10 days since the August 30 and yet detected no additional cases of rust.
"Since the find near Kinston is thought to be isolated and rust was at extremely low levels, the need to apply fungicides at this time is debatable," the experts noted in their Sept. 7 release. "We tend to think this is an isolated pocket of rust and there may be a few more, but likely not many. Our best guess is that a low level of rust arrived in mid-August, and it may take another two to three weeks before it has the potential to spread, provided we have conditions suitable for rust.
"Except for a few days this week when it will be in the 80's, hot temperatures are expected to return, which means that rust will develop very little in the next week. Thus we expect that it could well be two, and more likely three or four, weeks before we detect more rust. We expect to see a few small, possibly scattered, areas within fields located across the state that defoliate early and suffer some limited yield loss. It seems unlikely that affected areas will be large enough to justify the expense of spraying a fungicide unless more nearby sources of rust spores are found soon."
For more information on Asiatic Soybean Rust and where in the U.S. that it has been found in the current growing season, visit the Integrated Pest Management webpage on the disease at sbr.ipmpipe.org/cgi-bin/sbr/public.cgi