Asiatic soybean rust has been found on soybean in Decatur and Colquitt counties in Georgia, where conditions have been "quite favorable for spread," according to N.C. State University crop scientist and soybean specialist Jim Dunphy and plant pathologist Steve Koenning in their July 6 Soybean Rust Update.
In addition to those instances on soybeans, rust was also found on kudzu in Georgia in Decatur, Miller, Baker, Brooks and Lowndes counties.
"Weather has not been conducive to build up of rust with the high temperatures in North Carolina, thus it may be premature for North Carolina soybean producers to spray soybean for rust," the team wrote. "Be prepared, however, and remember that applications for Southern Rust of Corn may compete with fungicide/insecticide applications on soybean in terms of the numbers of aerial applicators and amount of fungicide available."
Dunphy and Koenning say vigilance will be "key" this year.
"Storms following a track similar to (tropical storm) Beryl could bring rust to North Carolina later in the year."
Dunphy and Koenning advise growers who are making decisions whether to spray a fungicide or whether to hold back, to consider these factors:
1. When will the corn reach maturity? Early maturing corn may escape infection so growers may want to concentrate on the later maturing hybrids.
2. Strobilurins provide excellent control of rust in general but their residual activity is short compared to the triazoles. Additionally, strobilurins have limited systemic movement in plants compared to triazoles such as Tilt, Folicur, Domark, Caramba, and Proline, and are thus not as forgiving of less than perfect application.
3. Application costs may actually be greater than fungicide costs in many instances; therefore consider using the higher fungicide rate, which will provide more residual protection and increase the likelihood of getting by with one application.
For the current status of Asiatic soybean rust and other pests visit http://sba.ipmpipe.org.