ISU Scientists Identify A Seed Treatment To Curtail Soybean Sudden Death Syndrome

Researchers at Iowa State University are leading a regional research project to identify farm management practices that help reduce Sudden Death Syndrome (SDS) in soybeans.

SDS is caused by a fungus that can destroy a small patch to an entire field of soybeans. Since its appearance 40 years ago, it has spread to most soybean-growing area in the United States and Ontario, Canada, and continues to move into new areas.

“In Iowa and the rest of the Midwest, SDS is emerging as the number two soybean disease after soybean cyst nematode, in terms of yield loss,” said Daren Mueller, assistant professor of plant pathology and microbiology at Iowa State and the principal investigator for the three-year regional research project, which began in 2013.

The project is partially supported by soybean checkoff funds through the North Central Soybean Research Program (NCSRP). Grant partners include Iowa State, University of Illinois, Michigan State University and Purdue University. The project includes researchers in Canada who are supported by the Grain Farmers of Ontario-Ontario Farm Innovation Program, a component of Growing Forward 2, a federal-provincial-territorial initiative.

The most widely used farm management strategy for lowering the risk of soybean SDS is to select plant varieties that have demonstrated resistance to the disease. But, as SDS continues to be a problem, farmers want more additional strategies, said Mueller.

Project objectives include determining if earlier or later plantings reduce the risk of SDS, studying the relationship between soybean cyst nematode resistance and SDS resistance, and assessing the effectiveness of new products, such as seed treatments and herbicides.

Researchers at Iowa State and the other land grant universities have been collaborating to study SDS for more than 10 years, with the support of the NCSRP. Leonor Leandro, associate professor of plant pathology and microbiology at Iowa State and co-principal investigator for the SDS management study, led the biological research that identified a DNA test that measures how much SDS pathogen is in the roots of a plant and in the soil.

Mueller says this biological research was foundational to being able to test management practices.

“If researchers didn’t have tools like this, we wouldn’t know what management practices we are testing are working,” Mueller said.

Other biological research included studying when infection takes place and if susceptibility to the fungus lessens as the plants get older.

“What we found is that the later the fungus infects the seedlings, the more resistance the plants had to SDS. That’s why we thought a seed treatment would be an effective solution. But we just didn’t see any products that were effective until recently,” said Leandro.

Leandro was referring to ILeVO, a seed treatment which Bayer CropScience asked to have included in all tests being conducted by the project universities. Bayer provided the seed treatment and the funds needed to double all of the experiments.

“Farmers are going to benefit because we have been able to identify a seed treatment that we now know works. Learning how it works, how it kills the fungus and what management practices will work — all of this knowledge is because of soybean research checkoff investment in the university system,” Mueller said.

Bayer CropScience has announced that the seed treatment, ILeVO, will be available for the 2015 growing season. Mueller says other products have since become available which they will include in future tests.