Caldwell County Agline

Current Status of Soybean Rust in North America

As of April 8, 2008, soybean rust is viable in parts of Florida, southern Alabama (Mobile area on kudzu), and Louisiana. Rust was found overwintering fairly far north in Mississippi on kudzu, but this site is now under water. Rust is active in Mexico on volunteer soybean growing in corn at this time on a limited acreage, but no soybean rust has been found on jicama (yam bean, a crop grown in Mexico on as much as 100,000 acres) because their rainy season has not started yet. Planting of sentinel plots in Florida is nearly complete, and many have been planted in Mississippi. Sentinel plot planting in Mississippi is currently on hold because many fields are under water and many if not all of their sentinel plots may have to be replanted.

Soybean Rust Summary for North Carolina: Reflections on 2005-2007

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. For the most part it has not required fungicide sprays. 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. We 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.

Soybean Rust Prospects for 2008

The potential for soybean rust to negatively affect North Carolina soybean production in 2008 appears greater than in the three previous years (2005-2007) ?at this time.?  I emphasize ?at this time,? since my crystal ball is no better than most, and this is mostly speculation for April 2008. 
Factors that may make soybean rust more of a problem in 2008 are as follows:

1. It seems that the La Nina effect that was at least partially responsible for the 2007 drought is breaking up, thus the chances for at least average rainfall or greater are improved.
2. Projected soybean plantings for 2008 to the south of us, Georgia and Alabama may well double in 2008.  Increased wheat plantings this year make it likely that more soybeans will be planted double crop to the south of us this year. This of course is partially dependent on soybean seed supply.
3. Some crop protection specialists are concerned that fungicide supply in 2008 may be limited because of increased use on the small grains this spring. There are reports that some wheat growers are already planning on two fungicide applications on wheat this spring (2008).
4. The large North Carolina wheat crop is likely to mean increased double-cropped soybean in 2008 which may be at greater risk to soybean rust. This again depends on the supply of seed.
   

Obviously, this is only speculation on our part. The transport of rust to North Carolina is dependent on numerous environmental factors, including weather to the south of us and environment during the growing season. Still greater vigilance seems warranted at this time.

Resources for Soybean Rust in 2008

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 available on the web at:

USDA soybean rust web site:
http://www.sbrusa.net/cgi-bin/sbr/public.cgi

North Carolina Agricultural Chemicals Manual soybean disease control recommendations:
http://ipm.ncsu.edu/agchem/6-9.pdf