Pest Alert: Soybean Rust Update
Date: October 8, 2012
From: Jim Dunphy, Extension Soybean Specialty, and Steve Koenning, Extension Plant Pathologist
With the confirmations announced over the weekend, South Carolina has found Asiatic soybean rust in a total of 17 counties, none of which are on the North Carolina border. More than three weeks after we found rust in Robeson and Johnston counties in North Carolina, we still haven’t found any more rust, including in those two fields, in several nearby fields, and in the nearest sentinel plots. All of our sentinel plots have been checked in the past three weeks as well. This reinforces the principle that if weather conditions do not favor the development of this disease, it is likely to develop more slowly than we know it can develop with ideal weather conditions. Currently, rust has been confirmed approximately 85 miles from Charlotte, 140 miles from Elizabeth City, 15 miles from Fayetteville, 15 miles from Murphy, 35 miles from Raleigh, 80 miles from Washington, 75 miles from Wilmington, and 80 miles from Winston-Salem, North Carolina.
We do not recommend spraying soybeans with a fungicide to control Asiatic soybean rust if they are blooming (or past 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). The higher labeled rates tend to provide more days of prevention, and may thus require fewer applications. Be sure to check the fungicide label to see how many times it may be used in a season.
Most of our North Carolina soybeans are close enough to maturity that rust will not have enough time to become much of an economic problem. Typically, more than 90% of our state’s soybeans will have dropped their leaves within the next 30 days.
The current status of soybean rust in the U.S. can always be found at http://sbr.ipmpipe.org/cgi-bin/sbr/public.cgi.