Soybean Rust Update
Asiatic Soybean Rust has been confirmed in more counties in the Gulf states than this early, in any previous year. So far this calendar year, rust has been identified in 9 counties in Alabama, 14 counties in Florida, 4 counties in Georgia, 12 parishes in Louisiana, and 6 counties in Mississippi. Most of the finds have been on kudzu, except for nine parishes in Louisiana, where rust has been confirmed on volunteer soybeans from January 26 through April 26. All these parishes are more than 450 miles from Murphy, NC, and farther than 450 miles from any soybeans east of Murphy.
Of greater concern is a report of rust on a blooming sentinel plot in Gadsden County, FL. (in the Florida panhandle near Quincy) on June 2 of this year. Given the path of Hurricane Colin last week, the likelihood of someone finding rust closer to NC (or even in NC) this week or next is greater than it would have been without the hurricane. Quincy is about 320 miles from Murphy, NC, 390 miles from Charlotte, and more than 400 miles from any soybeans north or east of Charlotte.
I still consider Steve Koenning’s (recently retired Extension Plant Pathologist) and my recommendation to not spray blooming soybeans that are more than 100 miles from confirmed presence of rust on soybeans to be a valid recommendation for most soybeans in NC. I do not recommend spraying for rust after stage R6 (full-sized beans in the top four nodes), since soybeans this mature will probably drop their leaves naturally before rust will cause many to drop prematurely. Check the label on the fungicide you prefer to use to see how late in the season that chemical may be sprayed.
The current status of rust in the continental US can be found anytime at http://sbr.ipmpipe.org.