Database Research Summaries
A current assessment of the foliar soybean diseases in Iowa

calendar_today Year of Research: 2018
update Posted On: 05/23/2019
group Steve Whitham (Principal Investigator, Iowa State University)
bookmark Iowa Soybean Association

Research Focus

The focus of this project is to identify the pathogens affecting the Iowa soybean crop during recent growing seasons in order to answer questions about what pathogens are present, have known pathogens changed, and what new problems could emerge.


  • Survey for pathogens causing known and unknown diseases.
  • Communicate research results with farmers and agribusiness.
  • Associate causal organisms with diseases of unknown cause.
  • Communicate results with diagnostic clinic and form strategy to develop diagnostic assays for unknown diseases.


  1. Leaves and stems were collected from diseased plants found growing from late summer through fall. A total of 49 samples were collected from different IA counties and stored at minus 80 degrees Celsius. The samples represented a wide spectrum of different symptoms that included diseases that could be tentatively identified and those that could not be identified. Diseases that were tentatively identified were: Phyllosticta, midge gall, tan spot, Septoria brown spot, SVNV, downy mildew, Cercospora leaf blight, and frog eye leaf spot. Unknown diseases had an array of symptoms including: virus-like symptoms, different sizes and shapes of necrotic spots (some surrounded by yellow tissue), top die back, necrosis with an orange/yellow halo, and bud proliferation.
  2. Total RNA was extracted from the 49 diseased tissue samples, we have identified several known and unknown viruses that were present in Iowa soybean fields during the 2017 growing season. Viruses that were identified during the 2017 growing season in IA county are as follows: Alfalfa mosaic virus (AMV) in Hancock county, Bean pod mottle virus (BPMV), Soybean dwarf virus (SbDV), Soybean vein necrosis virus (SVNV), Tobacco ringspot virus (TRSV) in Hancock; Story county, and Tobacco streak virus (TSV) in Story county. We have also validated the present of ClYVV and TRSV by performing infection assays on Nicotiana benthamiana plants.
  3. During the 2018 growing season, we collected 43 samples corresponding to diseased plants found in soybean fields from across the state of Iowa. None of these diseased samples could be diagnosed as being caused by a specific pathogen, but many appeared to have virus-like symptoms.


  • Farmers, agronomists and ag industry will have a better idea of pathogens infecting soybean, including new ones. We have confirmed the identification of new virus, Clover yellow vein virus, in a soybean plot in the recent growing seasons, and we have evidence that infection by multiple viruses may be common.
  • Researchers and diagnosticians will have information about possible new detection methods for soybean pathogens.
  • Preliminary data will be collected to revisit recommendations for screening soybean seed for presence of pathogens.
  • Background data will be collected to start assessing the role of infection by new pathogens on yield loss.

For more information about this research project, please visit the National Soybean Checkoff Research Database.

Funded in part by the soybean checkoff.