1. Evaluate inputs and tactics to manage sudden death syndrome (SDS) and brown
stem rot (BSR) of soybean
Background. SDS and BSR are among the top 10 soybean diseases in the NC Region based
on USB-sponsored yield loss estimates, and are likely among the top five most important
diseases in Minnesota. These diseases occur in favorable weather conditions, and have been
associated with soil population levels of their fungal pathogens. Soil populations of the
pathogens may also influence efficacy of soybean disease resistance. Crop rotations can
suppress BSR, however, without knowing the pathogen population in the soil, it is only a guess
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as to how effective the rotations are and when BSR-susceptible varieties can be planted with
minimal risk. Because SDS and BSR are threats to soybean production in Minnesota, we need
to understand risk factors and disease management options. BSR occurs in all soybean
production areas of MN, however, SDS is spreading, becoming more common north and west
in MN where it was previously uncommon. SDS has become more common with wet summer
weather patterns. Thus, SDS is becoming a bigger problem in more areas, including more
areas where high levels of resistance in locally adapted varieties is limited or absent. Three
seed treatments are sold for management of SDS, but the use of some of them is an
expensive input cost that may or may not pay-off with increased yields. There is a need to
understand and compare new and ‘old’ management options for Minnesota.
Goals and Approach/Methods:
Goal A. The goal is to determine the benefits of three seed treatments (ILeVO®,
Saltro®, and Heads-Up®) and resistant soybean varieties for management of SDS. Field trials
will be conducted at two inoculated and irrigated field locations (Rosemount and Waseca) with
combinations of the seed treatments and soybean varieties with different levels of SDS
resistance. Plots will be evaluated for the severity of SDS and for soybean yield.
Goal B. Determine the effects of pathogen populations in soil on development and
management of BSR and SDS. The research for this objective will be done in at U of MN
Research Facilities in Waseca and Rosemount. Replicated studies will be used to evaluate
different combinations of soil pathogen population (different quantities of infested grain and/or
pathogen spores), and crop residues on SDS and BSR development. The plots will be treated
with different amounts of these three factors. Soybean varieties with and without SDS and
BSR resistance will be planted, and disease development and seed yield will be assessed in
all treatments to determine how each factor influences disease development and yield.
Quantitative PCR will be used to estimate pathogen populations (inoculum potential) in soil
and infection of plants. Complementary research with the same treatments will be conducted
in replicated studies under controlled environmental conditions in a greenhouse. In addition,
soil samples from crop rotation plots will be collected from Waseca to determine the effect of
rotation on populations of the BSR pathogen in the soil.
Goal C. Evaluate soybean breeding lines and varieties for resistance to BSR.
Advanced breeding lines from the U of MN soybean-breeding program as well as selected
common commercial soybean varieties will be evaluated for resistance to BSR. This work will
be conducted in cooperation with Dr. Aaron Lorenz. This research will be conducted in a
greenhouse under controlled conditions. Plants at the VC/V1 growth stage will be inoculated in
replicated studies with two types (A and B) of the BSR pathogen. BSR severity and plant
growth will be measured after the R6 growth stage.
2. Determine distribution of Frogeye Leaf Spot in Minnesota and evaluate fungicide
activity against Minnesota isolates of the causal pathogen
Background: Frogeye leaf spot (FLS) has been a significant disease of soybean across the
southern half of the U.S. for many years, and in the past two years has been increasing in
distribution and severity in Minnesota. There is a need to understand its distribution and
sensitivity to fungicides that could potentially be used to manage it.
Goals and Approach/Methods:
Goal A. Determine the distribution of frogeye leaf spot in MN. Collect soybean leaf
samples with symptoms typical of Frogeye leaf spot from fields across Minnesota and confirm
that the FLS pathogen Cercospora sojae is associated with the symptoms. Leaf samples with
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symptoms of FLS will be collected from fields where symptoms appear and taken to my
laboratory in St. Paul for analysis.
Goal B. Evaluate efficacy of fungicides against the FLS pathogen (Cercospora) from
soybean leaves in Minnesota. The FLS pathogen will be tested in a laboratory for sensitivity to
different fungicides that could be used to manage it.
3. Conduct extension education and diagnostic activities that address important and
unusual soybean disease problems in Minnesota.
Background: There is an ongoing need to develop and deliver management information and
new research results across Minnesota for soybean diseases. In addition, unusual disease
outbreaks occur in fields across Minnesota each year for which specialized diagnosis and
focused efforts are needed to help famers understand the problems and to identify and
develop response strategies.
Goal A. Disseminate information, and teach and organize specialized meetings and
workshops to address soybean disease information needs for soybean producers.
Goal B. Perform specialized diagnosis of unusual soybean disease problems from
Minnesota and address problem fields when special disease situations occur.