Research HighlightsShaping Management and Input Options for Stem and Root Diseases
By Barb Baylor Anderson
Soybean stem and root diseases can limit yields, are difficult to manage and occur in response to weather patterns and other factors farmers must monitor. To find solutions, the Minnesota Soybean Research & Promotion Council is funding research led by Dean Malvick, University of Minnesota Extension specialist for field crops diseases, to evaluate inputs and tactics to manage sudden death syndrome (SDS), frogeye leaf spot (FLS) and brown stem rot (BSR).
“SDS is a major soybean disease across the major soybean-producing states, including Minnesota, where it is spreading and causing more problems in areas where it has not before,” says Malvick. “FLS has long been a significant disease in soybeans across the southern half of the U.S., and in the past few years has been increasing in distribution and severity in Minnesota. BSR is common and can cause significant damage across the state when susceptible soybean varieties are planted, and when weather conditions favor the disease.”
Malvick is exploring the value of specific seed treatment inputs and management tactics for the three diseases to help improve disease management. Last year, he evaluated inputs and tactics to manage SDS and BSR, determined distribution of FLS in Minnesota and worked with colleagues to evaluate fungicide efficacy against Minnesota isolates of the causal pathogen.
The research yielded several key outcomes last year of value to soybean farmers:
- Resistant soybean varieties, ILeVO and Saltro seed treatments effectively manage SDS. The resistant varieties and seed treatments were effective alone and in combination (with an additive effect) to manage SDS.
- Frogeye leaf spot (FLS) continues to spread across central and southern Minnesota. Most isolates of the FLS fungal pathogen appear to be resistant to QoI (strobilurin) fungicides.
- The level of resistance to brown stem rot (BSR) was determined for a set of advanced breeding and existing soybean lines from the University of Minnesota breeding program. Some varieties differed in susceptibility to the A and B types of the BSR pathogen.
- Multiple diseased soybean samples were diagnosed and management options determined.
Based on the research results, Malvick has established some management advice for farmers. When it comes to SDS, plant resistant varieties and/or use selected seed treatments effective against the disease. Similarly, to control BSR, plant resistant soybean varieties. If BSR has been a serious problem in the past, rotate away from soybeans for multiple years, if possible.
“FLS in Minnesota is a growing problem that has rarely reached levels of severity that warrant deliberate management tactics,” he adds. “But if the disease continues to increase, an important management strategy will be scouting for disease and then applying a fungicide containing an adequate level of a triazole and/or SDHI active ingredient to manage FLS.”
Malvick’s work on stem and root diseases has continued into 2021. “Additional research is needed for each of these diseases,” he says. “Results for BSR and SDS are applicable to other states, but the results for FLS are going to be primarily useful in Minnesota.”
This project was funded by the soybean checkoff. To find research related to this research highlight or to see other checkoff research projects, please visit the National Soybean Checkoff Research Database.