Soybean Rust Update
August 30, 2012

from Jim Dunphy, Extension Soybean Specialist,

and Steve Koenning, Extension Plant Pathologist

NCSU

 

Asiatic Soybean Rust has been confirmed closer to most of North Carolina’s soybeans with the announcement that rust has been confirmed in Dorchester County, South Carolina.  This is this year’s first confirmation of rust in South Carolina, and  puts rust approximately 145 miles from Charlotte, 330 miles from Elizabeth City, 160 miles from Fayetteville, 165 miles from Murphy, 215 miles from Raleigh, 260 miles from Washington, 170 miles from Wilmington, and 205 miles from Winston-Salem, NC.             We do not recommend spraying soybeans with a fungicide to control Asiatic Soybean Rust if they are not yet blooming, if they are blooming but rust has not been confirmed within 100 miles, or if full sized seeds are present in the top of the plant (stage R6).  Such pre-bloom applications have seldom improved yields, and repeated applications will likely be needed to provide season-long protection against rust.  The higher labeled rates tend to provide more days of prevention, and may thus require fewer applications.  The triazole fungicides, alone or in combination with a strobilurin fungicide, will probably provide better prevention of rust than a strobilurin alone.  Be sure to check the fungicide label to see how many times it may be used in a season.             An exception to the above recommendation is if Asiatic Soybean Rust is found on the farm before bloom, spraying a fungicide to the rest of the fields on the farm is recommended.

 

The current status of soybean rust in the U.S. can always be found at http://sbr.ipmpipe.org/cgi-bin/sbr/public.cgi.