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Corn+Soybean Digest

GUARDING Against Rust

While U.S. farmers prep their equipment for spring planting, harvest is well underway on the rolling plains of Paraná, a southern state in Brazil. With every pass of the combine, farmers there breathe a sigh of relief that they've dodged the devastating disease Asian soybean rust for one more season.

Farmers in this region of Brazil face different challenges from their neighbors to the north who farm closer to the equator. The weather is more variable, thus the threat of rust is not as consistent and the methods of defending against the disease are somewhat different.

Brazilians learn more about how to control rust every year, says Olavo Corrêada Silva, who has researched the disease for four years at Fundação ABC. Fundação ABC is a private research facility in Castro, Paraná, funded by three farmer cooperatives in the region and was a stop for ag journalists during a recent Syngenta-sponsored tour in Brazil.

Silva says there isn't one overall strategy for controlling rust. “In some parts of the world the disease is endemic — it occurs every year — while in other areas there are years when the disease doesn't occur at all. Different climates face different challenges,” he says. “In northern Brazil it's hotter and there's more moisture, and the disease occurs every year. In southern Brazil we have cooler temperatures and much less rain. Because of these differences we must have different control strategies in the north and south.”

Because it's so difficult to find the disease early enough, the cooperative has an established strategy to control it effectively.

They've built an information network that includes monitoring eight weather stations and scouting sentinel plots twice a week. Data is gathered daily, areas of high risk are mapped and information is posted on the cooperative's Web site.

Silva has also conducted research on the effectiveness of preventative vs. curative treatments. The strategy in that region is to protect the plant when it is most vulnerable — at R1.

He says this first application is important because fungicides have proven to be an effective preventative. Curative effects have been hit and miss.

“Until 5% severity, curatives are effective, but after that they may or may not work, depending on the amount of disease present. Timing is everything,” Silva says.

He has also been studying the effectiveness of a second spray at R4, comparing applications of triazoles with a combination of triazoles and strobilurin, and those have been effective.

Silva says that until resistant soybean varieties can be found, the triazole fungicides are the most effective defense against rust. But he also cautions his growers to manage the use of the products carefully to guard against resistance to the fungicides.

His message to U.S. farmers: “Don't panic. If the disease is detected early, there is no problem.”

Albertino Perez is the agronomist and manager of farms owned by Henrique and Anselmo Alberti in Tibaji County, Paraná. They farm 7,090 hectares (17,725 acres) of cropland, raising corn and soybeans in the summer and wheat, oats and dry beans in the winter. They also have 7,000 head of cattle.

Rust was seen for the first time in this area last year. Perez says he's learned plenty from farmers who experienced heavy losses and has implemented preventative sprayings. This year there was rust pressure, but dry weather helped minimize the disease's damaging effects.

He and other farmers in the region typically spray preventatively at R1 and follow up with another fungicide application at about R5. However, many Brazilian farmers would typically spray at R5 to guard against other late-season diseases.

“The earlier you spray the better. It's better to spend the money and spray because it's better to prevent rust from getting to the crop,” he says. “Spraying preventatively is much better than waiting to spray until rust is discovered.”

Perez adds that the quality of spray equipment used to apply fungicides is crucial, especially making sure the sprayer is calibrated properly.

“You need to deliver all the potential of the product by getting a good spray that wets all the leaves, particularly at the bottom of the plant,” he says.

Perez adds that sentinel plots are an important tool in fighting rust, helping him to monitor the timing and volume of applications. However, he says growers shouldn't lose sight of the importance of monitoring other diseases, saying there's potential for significant yield loss unless he manages for all diseases.

Richard Dijkstra of Ponta Grossa County has not yet found rust on his farm. With 900 hectares (2,250 acres) of cropland (half in soybeans, half in corn during the summer season), he relies on the strategies developed by Fundação ABC to monitor the disease.

He watches his crops regularly and gets frequent reports from the cooperative. If rust is discovered 10 km (6.2 mi.) from his fields and weather conditions are favorable for rust, he knows it's time to spray.

This year Dijkstra sprayed a preventative at R1 and followed up with a second application a R5, this time a combination of strobilurin and triazole.

He times the second application based on weather conditions and where rust has been found in the region, as well as pressure occurring from other late-season diseases.

“The whole region is involved in fighting this disease — it can be very aggressive,” he says. “But that's why we rely on a preventative to help protect our yields.”


An update on soybean health issues from David Wright Ph.D., education director of the NCSRP's Plant Health Initiative

The “sentinel plot” program — soybean producers' early warning system for Asian rust

Controlling Asian soybean rust (ASR) is going to be paramount to profitable soybean production. That's why the North Central Soybean Research Program (NCSRP) has teamed up with the United Soybean Board (USB) and several federal agencies to create a “sentinel plot” program — an early-detection system for Asian rust.

The system will be up and running this spring, and will allow growers to monitor movement of Asian rust in the United States. It also will provide producers with a window of opportunity to make decisions regarding fungicide applications prior to ASR's arrival to your own fields.

Early-planted plots, monitored regularly

Developed by X.B. Yang, a plant pathologist at Iowa State, this new checkoff-supported program includes an extensive system of early-planted plots in 20 soybean-producing states, from the deep South to the northern Soybean Belt.

Plots will be located at university research fields or grower fields, planted 15 to 25 days prior to normal planting times, and monitored every three to seven days. If ASR spores are present, disease symptoms will appear in sentinel plots first.

Plot data and risk assessments available online

Trained experts will monitor the sentinel plots and feed information to a centralized USDA database. (Once ASR is identified in a sentinel plot, plant samples will be sent to USDA for immediate verification.) All information on the presence of ASR will be collected in the database, and immediately made available to experts and producers. You'll be able to access this information on the PHI Web site — — as well as link to the USDA Web site. We'll also use the database to develop state-specific risk assessments, to alert you of the need to spray preventative fungicides.

A broad-based partnership

A project of this scope requires the partnership of USB, USDA-APHIS, USDA-ARS and USDA-CSREES. By working together, pooling checkoff and government resources and expertise, we're able to increase the number of sentinel plots, and give all soybean producers a better handle on rust if and when it hits.

I'm really excited about this program's potential to help keep producers a step ahead of ASR, and to help you protect your bottom line. But there is still much to learn. I strongly suggest that you stay on top of ASR and do your research as planting season approaches. For more information, visit

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