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Soybean Rust: Issues and FactsJune 29, 2004 Listed below are some questions and answers from the Soybean Rust Teleconference. The known host list for soybean rust includes Lupine. Has it been tested on Texas Bluebonnet? To my knowledge Texas Bluebonnet has not been tested. --Glen Hartman Have seed treatments (fungicides) been evaluated for SBR control and, if so, what were the results? There has been limited testing on seed treatments, none protect the crop at the critical post flowering stage. --Monte Miles Be aware the pathogen is not seeborne. Experimental inoculations of seed with P. phakopsora do not result in sbr. So the question: "Have seed treatments (fungicides) been evaluated for SBR control and, if so, what were the results?" Seems off the mark to me. --Matthew Royer Why has SBR become such a concern now, especially when it was discovered long ago? Why is it just now a threat in the U.S.? Soybean rust is a threat to the US production because the aggressive species, the Asian soybean rust has been found in South America. Since its discovery in Brazil and Paraguay in 2001-2002 the pathogen has moved northward. With the increase in soybean production towards the equator in Brazil and increaded production in Central American, combined with the availability of other hosts in those countries a land bridge has been established. so the US in now under a greater threat than when the disease was isolated in Asia. --Monte Miles Is there any difference in efficiency in time and treatment (i.e. morning applications vs. noon vs. evening vs. night)? We have no information on this. --Monte Miles Which types of nozzles are recommended for canopy penetration and/or effective application? We are working on this and hope to have some preliminary results by next planting season. --Monte Miles It sounded to me that you suggested 70 days after planting as the "ideal" time for a single spraying operation. And that you based your judgment on the Zimbabwe data set. However, I would assume that Soy Asian Rust does over winter where soybeans are planted in eastern Zimbabwe and that it won't over winter here in Midwest. If that assumption is correct, shouldn't we expect a delay in infection as we move north in the US? If so, wouldn't that delay in expected infection also delay the "ideal" time of spraying? Asian soybean rust arrives in the main production areas of Zimbabwe at different times each year. Last season the first outbreaks were seen at R3. You are correct in the assumption that soybean rust will not over winter in the mid west, however I caution about being to general in assumptions about when it will arrive. If the wheat and corn rusts can be used as examples, most years they move in a wave pattern that can be followed from south to north, However, there are those years where the spores are picked up in the south and deposited as far north as Canada in a single storm, with out any reports of infection in the area in between. Spore production in the over wintering areas, weather patterns, and crop stage will all need to be taken into account to develop a forecast system, the forecast system will be the effective method to time a single application. There is a lot of information that will need to be obtained before this type of system will be effective. As of today, the best data set we have to work with is the data from Zimbabwe, That data set tells us that if you want to use a single application, then a well timed application is effective, in their epidemic (environment) that timing is 70 days after planting, However, if you are off in your timing then you will have yield losses. The data also tells us that to protect yield fungicides need to be used after flowering, Depending on the epidemic, the environment and the products 2 or 3 applications may be needed. The other thing that need to be understood it the product they are using has a curative effect and a 20 day residual. All fungicides are not the same, the application program for your area will have to be based on what products are available to the growers. If you wait to spray until after the disease reaches your area you will limit your option on products that will work. Once Asian soybean rust becomes part of our production problems fungicide programs will need to be in place as a preventative practice, Fungicides will need to be on the crop before the disease arrives, One of the lessions we should take home from Brazil, if you wait until it is on your farm to spray then it might be to late. I have a hard time supporting the idea of a single properly timed application. It is along the same ideas as market timing when you sell a crop or a stock. You might think you have it but how often are you wrong? --Monte Miles Would you expand on how did you come up with $0.2 to 2.0 billion/yr in damages caused by Asian Soybean Rust in the US? The calculations were the result of an economic model created by economists in the Economic Research Service of USDA specifically for soybean rust. I did advise them, but did not create or interpret that model. Their model is explained in their web document posted at www.ers.usda.gov. The citation of that document is: Livingston, M., R. Johansson, S. Daberkow, M. Roberts, M. Ash, and V. Breneman. 2004. Economic and policy implications of wind-borne entry of Asian soybean rust into the United States. Electronic Outlook Report OCS-04D-02 from the Economic Research Service of USDA, 22 pages. The exact estimates of the impact of soybean rust were $640 million to $1.3 billion net losses the first year of establishment in the U.S. and $240 million to $2.0 billion in ensuing years. The net losses not only included losses to soybean producers, but also livestock producers, other crop producers, and consumers. Losses to soybean producers included cost of fungicides and other production costs and lower net returns (from switch to other crops or lower yield). --Kent Smith Are you computing yield loss? Yes. Yield loss is estimated to range from 0 to 9.5%. The authors even feel that a yield increase is possible up to 0.9% from the use of fungicides that would control other fungal diseases of soybean. Some plant pathologists have felt that these losses are too low. However, one must remember that the study assumes the outbreak will occur in 2005 and adequate supplies of effective fungicides will be present as well as the means to apply them. --Kent Smith How about control cost (product + application)? Yes. The study assumes that cost of fungicide material and application per acre will be $25. The authors know this is relatively high (they estimate the average to be $19) but feel is provides some conservatism in the analytical assumptions without unduly affecting the overall outcome. --Kent Smith Did you consider externalities such as higher seed cost, yield potential drag associated with varietal resistance, grain quality docking, etc? No. These externalities were not considered in this report. The authors are working on another paper concerning soybean rust that will consider some of these externalities and others as well as draw parallels with similar plant diseases such as wheat stem rust. --Kent Smith For more information regarding the agenda for this session, please contact Susan Ratcliffe, North Central IPM Facilitator, North Central IPM Center, University of Illinois Department or Crop Sciences at (217)333-9656 or via email at sratclif@uiuc.edu Return to Conference main page
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