Soybean Rust Update
PEST ALERT
From: Steve Koenning Extension Soybean Pathology Specialist North Carolina State University and Jim Dunphy Soybean Specialist Crop Science
Current Status of Soybean Rust in North America ? March 2009
As of March 16, 2009, soybean rust is viable on kudzu in parts of Florida (including one site in the panhandle), two counties in southern Georgia, southern Alabama (Mobile area), several locations in Louisiana, and extreme south Texas. Rust is also active in Mexico, and a new potentially new host has been found in Mexico. The new find in Mexico has not been identified as to species, but is said to be quite common on road sides in Mexico. Planting of sentinel plots in will be underway in southern states and will resume when soils dry out.
Soybean Rust Summary for North Carolina ? Reflections on 2005-2008
Soybean rust has been detected in North Carolina every year since 2005. Rust was found in 17, 44, and 6 counties in 2005, 2006, and 2007 respectively. In spite of a favorable fall environment, rust was only found in six counties in 2008. Fungicides were not necessary to control rust and most foliar diseases were minor in 2008. Only in 2006 was it recommended that fungicides be sprayed in the southeastern counties on late planted late maturity soybean. Yield increases in these areas were on the order of 4 to 5 bushels per acre.
Soybean rust generally moves from south to north from Florida to Georgia and finally to North Carolina and Virginia. Much of this movement is by local spread which is relatively slow. Tropical systems that moved through the state from the south have resulted in either delivery of spores or provided an environment conducive for rust to develop. In 2005 this was Ophelia and in 2006 tropical storm Ernesto coincided with development of rust in North Carolina. There was some concern in 2007 when a tropical storm moved through in June which could have brought spores from Florida. This did not happen because Florida and South Georgia were extremely dry and if there was any spore production in Florida prior to this time it was very minor. You have to have spores for a transport event (movement from one location to another).
In general we will likely need a wet spring and a summer with lots of ?gray days? to have an epidemic that requires fungicide sprays over large areas of the state. This can be expected about one year in five to one year in ten in North Carolina. Dr. Jim Dunphy and I will continue to maintain a network of communication with County Extension Agents, CCAs, and consultants to provide warnings about the need to spray for rust. Sentinel plots will be planted in the next 30 days in most locations. In addition, have a teletip phone number 1-800-662-7301 (the same number as for the cotton insect update) with a message updated as necessary.
Resources for Soybean Rust in 2009
There are more resources for information on Asiatic soybean rust available this year, than in many years in the past. Some sources for more detailed information are listed below:
- The USDA soybean rust web site - www.sbrusa.net
- The North Carolina Crop Protection Manual - ipm.ncsu.edu/agchem/6-9.pdf
