On Nov. 6, the first U.S. case of soybean rust was found in Louisiana in a production field at a LSU AgCenter Research Station near Baton Rouge, La. A sample from this field sent to the APHIS laboratory in Beltsville, Md., was confirmed positive for Phakopsora pachyrhizi, the causal agent for Asian soybean rust.
Since then, teams have searched over 10,000 square miles for other occurrences of soybean rust and found additional samples that also have been confirmed to be positive. Search teams are fanning out across other Gulf South states looking for rust.
The LSU AgCenter, in conjunction with USDA, APHIS, ARS, and the Louisiana Department of Agriculture, worked together, following federal response guidelines, to investigate the problem. All of these organizations had collaborated and simulated rust exercises before it was found. It was necessary to follow strict protocol to identify samples.
Because the rust pathogen has been designated a “select agent” that can possibly be used by terrorists to threaten the United States, the FBI and Homeland Security were involved.
To put things in perspective, the introduction of soybean rust into the United States is not unexpected. We knew that at some point it was going to be introduced. Universities and governmental agencies had been proactive in studies on how to best deal with rust when it arrived.
In 2003, fungicide studies were conducted in St. Landry Parish, La., In 2004, they were repeated in Concordia Parish.
Section 18 labels were submitted in April to the EPA for review.
County agents and other AgCenter personnel looked for the pathogen in the state as they made visits to individual farms.
Rust in not new. Other countries have been dealing with it for years and are still growing soybeans.
Chemical fungicide sprays are used successfully to treat infected fields. Most fields require two treatments.
The Section 18 emergency exemption for Louisiana is in place and is being reviewed by the EPA. The review process will be completed before next season. When this has been concluded, lists of available products, including their efficacies and their costs, will be provided to growers.
Research generated in other countries will aid Southern farmers in making decisions. Variety selection becomes more important even though no commercial varieties are know to have resistance. High-yielding, well-adapted varieties must be selected. There is no wiggle room for unproven varieties. Fortunately, the variety database is large and there are plenty from which to choose.
In 2005, growers trying to decide whether to plant soybeans should factor two applications of fungicides into their budgets. Growers already using a fungicide will add only the cost of one more application. The estimated cost will be around $20 per acre.
If rust hits the crop early, fungicide applications will become standard in all fields. Fields not sprayed will become inoculum sources for other nearby fields. It is possible, however, that the inoculum load may be light in 2005, and only one application may be needed. Producers are urged to plant and spray their beans as groups for additional control.
Monte Miles, USDA research pathologist in Urbana, Ill., and one of the nation's top experts on rust shared the following thoughts:
Several fungicides will be available for controlling rust and they come in two classes: preventive and curative. Preventive treatments are applied during early reproductive stages of soybean growth before or just after infection occur. Curative fungicides stop rust after it has become established. Preventive treatments usually cost less than curative treatments. There is a residual amount of yield loss if the rust is established in the field and curative treatments are necessary.
Cultural practices may influence the yield losses and may help in its control. Row spacing, for example, can influence disease severity. The disease spreads faster in wide-row beans because of the wind-borne nature of the spores. Narrow row beans, however, provide a better microenvironment and promote greater spore production, resulting in hot spots in the field.
Early-planted beans may escape some of the initial infection, but international data on this subject is mixed. It is also possible the spore load will be lighter earlier in the season and could cause less damage to early-planted beans.
Bottom line: There is much to learn, and 2005 will be just the beginning. There is no reason to panic, but it is time to make tough decisions. We are going to get through this, but some things will change. Proper variety selection, preventive sprays, and timing of sprays will be important to having success.
Another strategy might be to stagger plantings to make sure all plants don't hit the reproductive stage at the same time, because your neighbors will need planes and ground rigs also.
We anticipate some acreage shifts for Louisiana next year. Areas where soybean profit margins are very slim at best will be hit hardest by rust. Producers there may opt to not grow beans at all or to shift to other crops. Where profit potential is better, soybeans will be grown successfully.
In the coming weeks, we are going to address the economics of rust and how it will affect producers.
If you have been putting out a full rate of Quadris and Topsin-M, you are looking at the cost of one more application. If you have been applying no fungicide, you are looking at two applications with a price tag yet to be determined but expected to be between $30 and $60.
David Y. Lanclos, Ken Whitam, Clayton Hollier, Ray Schneider and Boyd Padgett are with the LSU AgCenter.