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Pioneer Hi-Bred Researcher Cites Scouting Tips for Monitoring Asian Soybean Rust


After three complete growing seasons of Asian soybean rust (ASR) in the United States, there are signs the disease can potentially expand northward, and experts with Pioneer Hi-Bred, a DuPont business, recommend growers closely monitor soybean fields for any signs of the disease.

“Growers need to continue to be aware of ASR, and while we haven’t heard about any significant problems at this time, regular scouting for the disease is recommended,” says Paul Stephens, Pioneer research fellow.

Asian soybean rust, a wind-borne fungal disease, is an aggressive pathogen with the ability to significantly reduce yields. If the disease is scouted early, a fungicide application is effective.

To determine if the disease is present, look on the underside of the leaf, starting from the middle to lower portion of the plant. The leaf will have red to tan lesions with small spores. The spores are a confirmed sign of rust.

In the United States the pathogen survives winter on an overwintering host south of the freeze line. Throughout the growing season, the disease will continue to push further north into the Midwest.

“If the Midwest sees ASR, most likely it will be late in the growing season,” says Stephens. “If growers know rust is suspected south of their operation, and conditions are conducive – cloudy, cool and wet – a fungicide should be applied. The earlier the application is applied, the better the protection. Once soybean rust destroys leaf tissue, significant yield loss has occurred.”

One control option for growers is DuPontTM PunchTM fungicide which has been granted a section 18 quarantine exemption from the EPA in several states to control ASR. Punch™ provides preventive and curative control of ASR in both high and current low disease pressure. It contains flusilazole, a unique broad spectrum fungicide that provides superior residual control, rapid penetration of waxy leaves and gradual systemic redistribution. For more information on where to purchase Punch™, call 1-800-342-5247 or contact your local DuPont representative.

Pioneer has an intensive molecular marker research program to incorporate into soybeans native genes for resistance to ASR to protect growers against the threat of yield loss. The program is identifying ASR-resistance genes out of the entire Pioneer soybean germplasm collection then moving them into elite products, combining ASR resistant genes with Accelerated Yield Technology (AYT™) to develop the complete Pioneer package. Pioneer plans to commercialize soybean varieties carrying multiple sources of ASR resistance by 2013 in the United States.

ASR is a diverse pathogen and can change or evolve in some environments to overcome a resistance gene. The potential for different isolates or ‘races’ to evolve increases the challenge for developing durable resistance. Experiences with soybean rust in South America and Asia have demonstrated that single genes for ASR resistance can be overcome.

“Because rust can change so quickly and without warning, Pioneer is evaluating stacking rust resistance genes,” says Stephens. “Pioneer’s strategy is to stack resistance genes to offer a broader type of resistance.”

For high disease environments, stacking genes of resistance is more effective than a single gene defense.

“This type of defense against ASR offers growers a new level of protection and provides greater insurance against yield loss for soybean growers who may experience ASR,” says Stephens.

To monitor Asian soybean rust, visit If ASR is suspected, contact your local Pioneer sales professional or agronomist. Soybean tissue samples can be submitted to the Pioneer Diagnostic Lab (7300 NW 62nd Ave., Reid #33C, Johnston, IA 50131) to determine the presence of ASR. Growers can work with their local Pioneer representative for submission directions.


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