Research Highlights

Research Highlights
Soybean Stem Disease Survey Defines Issues in Illinois Fields

The Dectes stem borer, shown here, tunnels through the soybean stem, weakening the plant and causing lodging at harvest. A recently conducted survey showed this pest is expanding its presence, now as far north as central Illinois. The black lines running through the stem in this photo indicate Diaporthe fungi, which causes stem canker and other diseases in soybeans. Photo: Jason Bond, Ahmad Fakhoury

By Carol Brown

Scientists want to make sure their research is taking the right path, and sometimes a good way to ensure this is to conduct a survey. Outcomes can confirm or reveal the directions in which researchers are going or need to go. 

Southern Illinois University plant pathologists Jason Bond and Ahmad Fakhoury are carrying out this process through a project funded by the Illinois Soybean Association. Bond specializes in soybean stem diseases and finding out their incidence and severity in fields across the state is key to future research direction.

“We have a lot of assumptions on what’s going on with stem pathogens and stem insects in Illinois. We needed more information from farmers,” says Bond. “We surveyed farmers to find out what they are experiencing now and in the recent past. We want to know how they have managed stem diseases and pests. We asked them to send us actual soybean plant samples, and we collected plant samples from fields as well.”

The last survey in Illinois for stem diseases and pests took place about 20 years ago, so the information gleaned from farmers is important to ensure proper actions are being taken. Bond, Fakhoury, and entomologists Kelly Estes and Nick Seiter from the University of Illinois, worked closely with Illinois Soybean Association staff to develop the questions. ISA then sent the survey to Illinois soybean growers. Bond believes the association’s relationship with farmers is why they received great feedback from all over the state.

“Historically, the research focus has been on what is affecting soybean roots, as soybean cyst nematode is out there,” comments Bond. “There are a lot of seedling diseases and fungal diseases as well, so stem organisms get lost in the shuffle a little, but they are there and can impact yield directly and indirectly.”

This fall, Bond and Fakhoury processed the soybean samples they received from farmers, as well as the ones they collected. They identified diseases visually with microscopy and molecular techniques, which is Fakhoury’s expertise.

This petri dish contains soybean cyst nematodes amongst root debris collected from one soybean root, 45 days after planting. The yellow and white lemon-shaped females (examples circled in black) and cysts (examples circled in brown) all contain eggs that increase SCN pressure. Samples like this one were submitted by farmers and collected by Jason Bond and his research team as part of a statewide survey to find the incidence and severity of SCN and soybean stem diseases across Illinois. Photo: Jason Bond

“We are deploying molecular techniques to help confirm these diseases, especially some of those who are difficult to identify,” Bond says. “We are culturing them in the lab and assessing the isolates.”

They found an array of stem pathogens including the Diaporthe/Phomopsis complex, which causes a variety of diseases including stem canker. The team also found charcoal rot, Anthracnose and Phytophthora.

“Anthracnose and Diaporthe were spread around the state. We picked up patterns in the state of charcoal rot, which we can trace back to weather conditions,” Bond says. “We saw more Phytophthora and stem canker earlier in the growing season.”

Another component of the study included an assessment of insect pests found in Illinois soybean fields. Bond is working with Estes and Seiter, who conducted a separate insect survey. Estes is the state agricultural pest survey coordinator. 

“They found that the Dectes stem borer is now in a good portion of southern and central Illinois, stretching up into Indiana. Before, it was only in the very southernmost counties of Illinois,” Bond says. “This insect tunnels in and out of the soybean stem, causing plant lodging, which makes harvest difficult and leads to yield loss.”

The team is also scouting for the soybean gall midge, which has not been found in the state so far. They have a sentinel system at several sites in western Illinois, says Bond, to keep watch for the pest. 

Bond and his team are building a database of disease and pest ranges from the farmer surveys and plant sample assessments. In 2023, the second year of the project, they will be adding to the database by sampling more soybean fields themselves. Bond will also follow up with the farmers who previously sent in samples.

“We are going to provide those farmers with information on what was identified in their fields and in their area, both from a plant disease standpoint as well as insect pests,” Bond says. “We will also offer guidance to help them manage the diseases and pests present in their fields.”

Published: Mar 13, 2023

The materials on SRIN were funded with checkoff dollars from United Soybean Board and the North Central Soybean Research Program. To find checkoff funded research related to this research highlight or to see other checkoff research projects, please visit the National Soybean Checkoff Research Database.