Soybean Rust Concerns from Recent Tropical Storms may be Overstated

July 14th, 2005

Recent tropical storms along with Hurricane Dennis are unlikely to have moved Asian soybean rust spores any closer to Iowa according to an Iowa State University extension plant pathologist.

"Concerns about movement of soybean rust spores into Iowa are understandable but premature," said Alison Robertson, Iowa State extension plant pathologist. "The storms' paths have all been moving well east of Iowa."

Iowa State experts have been advising producers to wait until soybean rust is confirmed north of Interstate 70, which runs between Kansas City and St. Louis, before making decisions on applying preventative fungicide treatments.

Robertson said the guidelines would be adjusted as the season progresses based on crop conditions, weather forecasts and soybean rust movement in the south.

"Producers have to consider several factors before using fungicide treatments, such as growth stage and prevailing weather conditions," Robertson said. "Most Section 18-labeled fungicides can only be applied legally when soybean rust is imminent and conditions are favorable for rust development and should not be applied to manage other diseases or for plant health purposes."

Even when spores are present in the atmosphere, the environmental conditions must be conducive for the disease to occur, Robertson said. Frequent rain and cool, wet weather promote soybean rust development.

Robertson is part of the Iowa Soybean Rust Team that has been preparing Iowa for the disease for the past two years. The team has laid out a "fast track" reporting system for producers and crop professionals to submit soybean samples.

The "fast track" identification system was set up to quickly identify soybean rust in Iowa and efficiently manage samples submitted to the Iowa State University Plant Disease Clinic. The system is simple. Producers submit samples to first detectors who then send suspect samples to triage personnel for further diagnosis. Suspect samples are then forwarded to the clinic. The triage personnel include Iowa State Extension field and crop specialists throughout the state.

The Iowa Soybean Rust Team continually monitors the movement and status of the disease in order to provide up-to-date information to the public and producers. Experts are monitoring 30 sentinel plots in Iowa and have trained about 600 first detectors. The soybean rust team includes representatives from Iowa State University, ISU Extension, Iowa Department of Agriculture and Land Stewardship, Iowa Soybean Association and the U.S. Department of Agriculture Animal and Plant Health Inspection Service.

For more information about Iowa conditions and soybean rust, go to the Iowa Soybean Rust Team's website at


Alison Robertson, Plant Pathology, (515) 294-6708,
X.B. Yang, Plant Pathology, (515) 294-8826,
Keven Arrowsmith, Continuing Education and Communications Services, (515) 294-2405,
Barb McBreen, Communications Service, (515) 294-0707,