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C.O.R.N
Newsletter
2004-39
November 22, 2004 -
December 8, 2004
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Soybean rust has been found in the US, but will it survive?
by
Anne Dorrance
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Asian soybean rust finally reached continental US shores in one of the hurricanes late this past summer. It has been identified now in soybean fields in Florida, Georgia, Louisiana, Mississippi and surveys are in progress in the US and Caribbean to see how widespread soybean rust is and how many points of introduction there were. This will be very interesting, but also intriguing, those storms arrived in September, but rust was not detected until early November. Most soybeans in that area have been harvested and they are surveying kudzu and the few remaining soybean fields. Data from South Africa, Paraguay and Brazil, indicate that rust can be managed with 1 to 2 fungicide applications. In most regions the first application is applied at some point during the flowering period. Even though rust has been found far south of here, the answer to the question for Ohio producers about spraying fungicide during 2005 are the words might, maybe, possibly and depends. What we still don’t know are the following:
1. Will soybean rust overwinter in the gulf region? If this is killed out by a very cold winter, we will have to wait for the next hurricane or storm to bring it back into the US. Models from Iowa State predict that it could overwinter in southern Florida and southern Texas. Surveys in those areas next spring will tell if rust will survive.
2. If we are unlucky and it overwinters, when in the spring will those infections begin to form new spores to begin the movement north is the next piece to the puzzle. The when and how fast and on which storm will determine if and when we recommend fungicide applications.
3. What will the final list of EPA approved fungicides be by next spring? We have applied for 6 fungicides for use on soybean rust in Ohio. We are in the process of applying for an additional 4 materials. EPA (as of Friday) will not consider additional materials until the first 6 have gone through the process. This will be a changing dynamic over the winter and until the dust settles we will not have a good idea of what our choices will be. Depending on what materials are available, will determine our spray timings.
How to prepare for this pathogen. There are several things that you can do on your farm to prepare for soybean rust. The first is don’t worry. This is another pathogen or headache, but it is manageable. Our goal is to limit losses as much as possible and that includes not spending money that you don’t have to.
1. Your first priority is to make the best possible selection of varieties for your field situations for 2005. Eliminate un-necessary losses to other pathogens by choosing the best variety with the best resistance package. It is pointless to have rust come in and take that yield hit when you’ve already lost yield to other diseases such as Phytophthora, SCN and Sclerotinia. For Phytophthora, choose a variety with Rps1c, Rps1k, Rps3a, a combination PLUS high levels of partial resistance. For SCN, only use SCN resistance in fields with SCN populations around 2,000 eggs/cup of soil and rotate your fields.
2. Based on predictions, it looks like Ohio may have to spray for Aphids. In this event, consider planting your fields with tram lines or skip rows for spray equipment to move through fields at these later growth stages. This will help if rust does move north and we have to spray – we won’t be driving over beans 3 and 4 times during the growing season. It will also provide good spots to scout fields.
4. Learn the different growth stages of soybeans. Spray timing for many of these pests will be set by growth stages. If this rust does not arrive until after the R5 – we will not need to spray. Yield losses are minimal at later growth stages in all grain crops and it doesn’t pay to spray at these later times. We also have preharvest intervals to consider for many materials and we do not want beans sitting in fields any longer than necessary.
5. Learn to recognize soybean rust. There is a multitude of resources out there right now. A rust ID card will be in your county office in 2 weeks time. We will be covering this topic in depth at the OSU Agronomy Teams Crop Profit Game on February 15th. Your local county extension office will be the site for this satellite program.
6. You do not need to buy fungicides at this point. EPA is still reviewing many of the materials that were applied for Section 18 labeling. Many of these have higher efficacy and are more economical than some of the materials that are currently labeled. According to the chemical companies, they will move fungicides into regions as the disease begins to move. If it is controlled where it begins, that reduces the overall inoculum and slows the epidemic down to where we, and many northern states, may not have to spray on an annual basis. If this pathogen stays here in the US.
There are still a lot of unknowns, but fortunately for us, this came in November and we have the winter to solidify plans that were already in development and begin the education progress. Fungicides may or may not become part of our annual soybean production practice, but the keys to keeping this venture profitable:
• recognize when soybean rust is in the region,
• proper timing of materials and if they are economical to apply,
• proper choice of materials for the infection stage,
• thorough coverage of fungicides on the crop and targeting those low leaves in the canopy,
• Manage everything else to limit losses. |
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information, and appropriate recommendations for Ohio
Crop Producers and Industry. C.O.R.N. is produced by
the Ohio State University Extension Agronomy Team, State
Specialists at The Ohio State University and Ohio Agricultural
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Issued in furtherance of Cooperative
Extension work, Acts of May 8 and June 30, 1914, in
cooperation with the U.S. Department of Agriculture,
Keith L. Smith, Director, Ohio State University Extension.
TDD # 1 (800)
589-8292 (Ohio only) or (614) 292-1868
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