Soybean Seeds: A Look Ahead to 2019 Planting


The images above show a badly infected seed lot before treatment (left) and a seed lot with similar damage after being treated (right).  You will notice, the dead seeds that were white and fuzzy, are now fungus-free, but have bacteria on the surface.

Ames, IA - There may be a scramble to find good quality soybean seed for planting in 2019.   This comes after much of the soybean crop in the United States was plagued by unusually wet weather before the crop could be harvested in 2018. 

“The soybeans sat in the field too long due to rain and muddy conditions,” said Dr. Charlie Block, Iowa State University Seed Science Center (SSC) Seed Health Coordinator. “The combination of rain and delayed harvest was favorable to fungal infection.”

Block, a former USDA Plant Pathologist and ISU Plant Pathology and Microbiology Assistant Professor, has nearly 40 years of experience working with seed-borne pathogens.  He says the seed quality from the 2018 soybean harvest is considerably lower than what is seen most years. High levels of fungal seed infection and resulting poor germination are common. The main disease seems to be Diaporthe pod and stem blight, but the SSC Seed Laboratory has also seen high levels of Fusarium-infected seeds as well as discolored seeds due to frogeye leaf spot (Cercospora sojina) and purple seed stain (Cercospora kikuchii).

“In most years, you might find one percent of seeds infected with Diaporthe,” said Block. “But in 2018 we commonly found ten percent seed infection, with some seed lots running as high as 30 to 40 percent.” 

This comes after a USDA report in October predicted a larger than normal soybean crop.  Many farmers were hoping the increased yield would help offset their losses from lower prices.  But the rain just kept falling, encouraging spread of fungi to seeds from pods and also the deterioration of pods and plants.  Corn seemed to weather the conditions, but soybeans rotted, sprouted, or shattered.  

While this could mean lower soybean seed germination rates in 2019, Mike Stahr, SSC Seed Lab Manager says there is hope. While badly infected seeds won’t emerge when planted in the field and may not germinate, many of the seeds have only a mild or superficial fungal infection. A fungicide seed treatment will improve germination of seed lots with these types of seeds present.  Stahr indicated that the key point is that seed treatment can’t bring a dead seed back to life or add healthy tissue to a badly damaged seed, but it can make a very significant impact if a seed hasn’t reached the point of no return.  

The following images show a badly infected seed lot before treatment and a seed lot with similar damage after being treated.  The dead seeds were white and fuzzy in the first photo, are now fungus-free, but have bacteria on the surface.

“Seeds, which have been chemically treated, showed improvements in scores of up to 20 percent, with the most common improvement between 10 and 15 percent,” said Stahr. “At the December, 2018, American Seed Trade Association CSS Seed Conference held in Chicago, there were even reports of improvement up to 40 percent.” 

For more information on seed conditioning e-mail Alan Gaul, seed conditioning specialist at the Seed Science Center or call 515-294-4011.  For more information on testing “moldy” seeds and possibly improving results of testing, contact Dr. Charles Block (seed pathologist) or Mike Stahr (Seed Lab manager) at 515-294-6826 or e-mail  The Seed Lab web page is available at

About the Seed Science Center 
The Seed Science Center at Iowa State University is a center of excellence nationally and internationally in seed research, education, technology transfer and international seed programs.

Contact: Cynthia Hicks, Seed Science Center, 515-296-5386,