ISU Experts Respond to Confirmation of Asian Soybean Rust in Louisiana

November 11th, 2004

The U.S. Department of Agriculture (USDA) confirmed yesterday that Asian Soybean Rust has been found in Louisiana, the first known incidence of the disease in North America.

Asian soybean rust is an aggressive fungal disease that can reduce soybean yield substantially, said Greg Tylka, Iowa State plant pathologist. The disease has the potential to cause extensive damage to plants and can travel quickly through infected areas depending on environmental conditions.

Tylka said many scientists expect soybean rust to show up in Iowa during next year's growing season. He also said two variables will influence how soybean rust may affect Iowa's soybean crop in 2005; when the disease arrives and what the weather conditions are at the time it arrives.

"It's difficult to guess if soybean rust will be here in early July or late August, but if we're lucky it will be late August," Tylka said. "The weather conditions will be another concern. In 2004, we had perfect weather for rust, lots of moisture and moderate temperatures. If we have a hot, dry year soybean rust will be much less of a concern."

The soybean rust fungus probably will not overwinter in Iowa or other northern soybean-growing areas, Tylka said. In order to infect Iowa fields, the spores would have to be carried up from the southern United States by winds every year.

X.B. Yang, Iowa State plant pathologist, has studied soybean rust since 1989 and uses weather models and maps to track wind movements to predict where rust spores may be carried. He is one of the leading experts in the world and is a member of a USDA soybean rust detection assessment team. The team is examining fields today in Louisiana.

Prior to yesterday's announcement, the Iowa Department of Agriculture and Land Stewardship applied and received Section 18 emergency use permits from the EPA to allow producers to apply certain fungicides to manage soybean rust. The permits became effective with the USDA announcement yesterday. Tylka said he wants to put the arrival of the disease in the proper perspective and not have producers overreact and purchase fungicides unnecessarily.

"We should be ready to react quickly, but we need to be careful not to overreact," Tylka said. "If we identify soybean rust in Iowa, there still may be times during next year's growing season when it wouldn't make economic sense to spray."

Bob Wisner, Iowa State agricultural economist, said the additional costs associated with the management of soybean rust could influence spring planting.

"Farmers may shift some acres from soybean to corn because of expenses and the uncertainty of soybean yield prospects. I would not expect a major shift but there could be a modest shift," Wisner said.

The discovery doesn't impact the 2004 crop and came at an opportune time to prepare for next year, Wisner said.

"If there were a good time for soybean rust to enter the United States, that time would be now," Wisner said. "The fact that it was discovered after harvest allows time to prepare for the next growing season and that's a plus."

Tylka coordinated training sessions last summer for more than 400 certified crop consultants, certified professional agronomists and independent crop consultants as first detectors in a "fast track" reporting system. The fast track system was developed to speed up reporting of soybean rust. The system is simple: producers submit samples to first detectors at no cost. First detectors send suspect samples to triage personnel, who are Iowa State Extension field staff, for more diagnosis. The triage person then forwards suspect samples to the Iowa State University Plant Disease Clinic.

The fast track system is part of an overall action plan prepared by the Iowa Soybean Rust Team to quickly identify soybean rust and efficiently manage samples submitted to the Iowa State Plant Disease Clinic. The team has worked for the past two years preparing to respond to the introduction of Asian soybean rust into the United States and Iowa.

Team members represent Iowa State University, the Iowa Department of Agriculture and Land Stewardship, the Iowa Soybean Association/Iowa Soybean Promotion Board and the United States Department of Agriculture Animal and Plant Health Inspection Service. More information about the team and its action plan are available at http://www.soybeanrust.info.

Asian soybean rust was first recorded in Japan in 1902. The pathogen moved throughout Asia, Australia and Africa before it was discovered in South America in 2000. Asian soybean rust has been moving northward through South America and was recently reported north of the equator.

Contacts: 

Greg Tylka, Plant Pathology, (515) 294-1741, gltylka@iastate.edu
Bob Wisner, Economics, (515) 294-6310, rwwisner@iastate.edu
Barbara McBreen, Communications Service, (515) 294-5616, barbmc@iastate.edu

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