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Monitoring and Management of Soybean Rust in Alabama

Soyabean rustThe objective of this program was to assist soybean farmers in Alabama and other soybean growing areas of the U.S by monitoring the spread of Asian soybean rust in 2006, and informing growers about timely and effective management of the disease. Asian soybean rust (ASR), a destructive fungal disease of soybeans, was first detected in the United States in 2004, and spread as far north as Kentucky in 2005. A USDA-ERS economic risk analysis projected that the potential losses in the U.S. could be $7.1 billion per year, once soybean rust was established in the main soybean growing area of the United States. A conservative prediction indicated yield losses greater than 10% in nearly all the U.S. soybean growing areas with losses up to 50% in the Mississippi delta and southeastern coastal states. Timely fungicide sprays can protect soybeans from the disease, but can be costly (approximately $20 - 40/Acre for two protective sprays), and unnecessary if the disease is not present. Since ASR needs live green leaves of a host such as soybeans or kudzu to survive, it was expected to overwinter in warmer areas and move northward in the spring.

Soybean Rust Activities Conducted by the Alabama Cooperative Extension System (ACES) Field Crops team in 2006

Education
In preparation for soybean rust, grower education was made a priority by members of Field Crops Team prior to the growing season. Twelve county and regional soybean production meetings programs were conducted with over 400 growers attending, with updates and lessons learned from the 2005 season. In addition to in-state programs, Team members were also were invited to speak about their experiences with ASR at conferences in Illinois, Iowa, Georgia, Tennessee, Ohio, Kentucky and North Carolina with over 800 people attending.

An Extension Circular was developed on identification and management of soybean rust in Alabama, direct mailings were made to Alabama soybean growers, and a Soybean Rust Web site and Soybean Rust Hotline: (1 800-446-0388) were updated regularly to keep growers and their advisors informed.

The Alabama Soybean Rust Sentinel Plot Network
A sentinel plot network for early detection of ASR was established with support from the USDA-APHIS and the Alabama Soybean Producers (checkoff funds), in coordination with the USDA National Soybean Rust Sentinel and Monitoring Network. Twenty soybean sentinel plots were planted at Auburn University Research Stations or in fields of cooperating growers. These plots were typically small (50 x 50 ft minimum) areas planted two weeks prior to the standard planting date for the area with two soybean maturity groups to lengthen the monitoring season. In addition to the soybean plots, 16 kudzu patches were also monitored weekly for the disease, beginning in January and continued through December. Random commercial soybean fields and kudzu patches were also scouted for rust during the growing season.

Sentinel plots were scouted weekly by Regional and County Extension Agents County Agent Coordinators, Specialists and other Extension trained scouts. Suspect leaf samples were also shipped by express mail to the AU Plant Diagnostic Laboratory for incubation and microscopic examination. By late November, over 27,000 soybean leaves had been examined at the ALFA Agricultural Services Building, in addition to the large number of leaves that were examined by Extension crops team members in the field.

Four ASR spore traps were also checked weekly by Extension personnel, in cooperation with the University of Arkansas and Syngenta agrichemical company, to determine if this method could give Alabama producers an even earlier warning of ASR movement into their area.

Overwintering soybean rust was detected on kudzu as far north as Montgomery, but extremely dry weather slowed its spread, with first detection on soybeans in a sentinel plot in Baldwin County on June 29. As of December 31, 2006, soybean rust had been detected in 26 Alabama Counties. All monitoring information was regularly updated on the USDA National Soybean Rust Sentinel and Monitoring Network public website www.sbrusa.net, keeping growers across the U.S. informed of ASR’s movement.

The Soybean Rust Telephone Hotline (1-800-446-0388):
The Auburn University Soybean Rust Hotline was maintained with weekly updates to provide Alabama growers timely information on soybean rust. Updates included observations on the movement of soybean rust in Alabama and the U.S., along with fungicide guides and recommendations when needed. Many growers reported that they called the “hotline” frequently during the 2006 growing season. In addition, many growers from other states called the Auburn Hotline to keep track of ASR movement in the South.

Educational meetings prior to the growing season were attended by more than 400 producers and increased their knowledge base on the disease. The meetings gave growers a better understanding on how to combat the disease if it appeared in their area. Growers were given literature that focused on soybean rust identification and included guidelines on proper fungicide usage.

Because of intense monitoring by team members, and the severe drought, few fungicide applications were made by Alabama growers for rust control in 2006. A fungicide application for soybean rust would typically cost about $20/acre. Prior to the season, we anticipated that most growers would spray at least once for the disease during 2006. With approximately 160,000 acres of soybeans planted in 2006 we estimated the cost of spraying at about $3 million. Because of our educational programs prior to the season and the intense monitoring program conducted during the growing season we were able inform growers that fungicide applications in the majority of counties were not justified to control soybean rust in 2006. Confidence in Extension monitoring and educational efforts by soybean producers resulted in a significant number of growers not spraying for the disease, with estimates of less then 10% of the soybean acres sprayed. This resulted in a grower savings of over $2.5 million in application costs, while still protecting the soybean crop from damage from Asian soybean rust. An even greater impact of the program was felt nationally, as growers in Midwestern and other states with much larger soybean acreages closely tracked the Alabama and national monitoring efforts. Assuming that 50 million acres in the U.S were not unnecessarily treated for ASR, because of grower confidence in monitoring efforts, over $1.0 billion in fungicide application costs were potentially saved by U.S. soybean growers in 2006.

Improving the Cost/Benefit Ratio of IPM

For More Information, Contact:
Edward Sikora

Professor and Extension Plant Pathologist

163 ALFA Agricultural Building

961 S. Donahue Drive

Auburn University, Alabama 36849-5624

334-844-5502

Email: sikorej@auburn.edu


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