Wisconsin Soybean Disease Update – June 19, 2014

Damon L. Smith – Extension Field Crops Pathologist, University of Wisconsin

Soybean planting has finally finished up for our research program.  We planted our last, late planting date trial this week.  Soybeans around the state have emerged and are at the VC or early V1 stage.  Several diseases have been noted already this year in soybeans.

Figure 1. Septoria brown spot on a soybean seedling.

Figure 1. Septoria brown spot on a soybean seedling.

With all of the rain we have been seeing early symptoms of Septoria brown spot (Fig. 1).  This is a common disease of soybean in Wisconsin and is caused by the fungus Septoria glycines.  While scouting a field near Fond du Lac this week, we observed the characteristic purple-brown lesions (Fig. 2) caused by this fungus, on the unifoliate leaves of soybean plants.  This isn’t unusual considering the moderate temperatures and frequent heavy rain.  The spores of this fungus are typically rain splashed from old soybean debris, to the growing plants.  Septoria brown spot is usually not considered a yield limiting disease, but in certain cases, it has been attributed to significant yield loss.  This is usually the case where a susceptible variety is grown in a location conducive to the disease and rain is frequent and heavy.  In a situation like this, fungicides might be required during the reproductive phase of growth to preserve yield. However, most of the time, Septoria brown spot is observed early in the season and again late in the season during periods of heavy rainfall and does not affect yield.  I suspect, once the rain subsides a bit, this disease will also subside.  However, growers and consultants should keep an eye on it just in case it does not.  To learn more about Septoria brown spot, visit the brown spot information page by clicking here.

Figure 2. Purple-brown lesions characteristic of early Septoria brown spot symptoms.

Figure 2. Purple-brown lesions characteristic of early Septoria brown spot symptoms.

Reports of seedling diseases are also starting to roll in as a result of the very wet conditions and frequent rainfall.  Pythium damping off and root rot is a likely culprit in many of these fields. Cool wet soil conditions at planting and during seedling emergence favor this disease.  There are many species of Pythium that can infect soybean and soybean pathologists are currently conducting a study to identify these species.  An informative pocket guide has been developed.  You can download a PDF version of the pocket guide by clicking here.  You will note that management focuses on adjusting planting date and using seed treatments to protect against infection by Pythium species. Foliar fungicide application is NOT recommended for this disease.

Other seed and seedling diseases might also be plaguing soybeans with all of the wet weather.  Other pathogens include Rhizoctonia and Phytopthora.  To learn more about other seed and seedling issue of soybean in Wisconsin, click here and scroll down to “seedling diseases.” You will find helpful resources pertaining to many of the common seedling issues.  Also for specific information on Phytopthora root and stem rot of soybean, you can download a UWEX fact sheet by clicking here.

Growers and consultants should scout soybeans for disease frequently during this cool wet weather.  Hopefully the rain will subside soon.  Some dry weather will help slow down the advancement of many soybean diseases.

Soybean Disease Considerations for Planting into Cool, Wet Soils

2014 Soybean Research Plot Planting

2014 Soybean Research Plot Planting

Damon L. Smith – Extension Field Crops Pathologist, University of Wisconsin

The 2014 soybean planting season has been painfully slow this season in Wisconsin.  In our research trials we have managed to plant at a couple locations, but the majority of our soybean plots have not been planted.  Looking at the forecast for the next several days, I suspect we will be further delayed.

To add further insult to injury, are the cool and wet soil conditions.  Even if we do manage to plant some plots in the next few days, the soil temperatures remain in the lower 50 degree Fahrenheit range in the southern part of the state, and likely cooler as we move north.  All of the rain is also keeping the soil very wet.  These conditions are very conducive for various seed and seedling diseases of soybean.

Last season I wrote a Wisconsin Crop Manager Article about this topic. Rather than recap that article, you can visit it directly by clicking here. In the article I talk about some likely diseases of soybean under these conditions. I also direct you to some helpful links about seed treatments and resistance genes for Phytophthora management.

We also recently developed a fact sheet on Phytophthora Root and Stem Rot of Soybean that might also be helpful.  This fact sheet can be downloaded by clicking here.

Heres to hoping we can all plant soybeans soon!


New Publication on the Relationship between the Causal Agent of SDS and SCN in Wisconsin

New for 2014 is a publication describing the latest research on the relationship between the causal agent of SDS and SCN in Wisconsin soybean fields.  CLICK HERE to download a PDF.SCN&SDS

2013 Update – A3878 – “Fungicide resistance management in corn, soybean, and wheat in Wisconsin”


A3878 - Fungicide resistance management in corn, soybean, and wheat in Wisconsin

A3878 – Fungicide resistance management in corn, soybean, and wheat in Wisconsin


A3878 – “Fungicide resistance management in corn, soybean, and wheat in Wisconsin” was developed by the University of Wisconsin UW Extension and the Nutrient and Pest Management Program, and has been updated for 2013!  Significant additions include small grains seed treatments now on the chart.  In addition, all trade names and active ingredients have been brought up to date according to current pesticide labels in Wisconsin.  A hardcopy of the chart can be requested by email at npm@hort.wisc.edu.  You can also download a PDF version by visiting the Nutrient Management and Integrated Pest and Crop Management Publications.

2012 Wisconsin Soybean Variety Test Results







The results of the 2012 Wisconsin Soybean Variety Trials can be viewed and downloaded as a PDF at http://soybean.uwex.edu/soytrials/printable/documents/Soybean_NPM_FINAL_WEB.pdf.  The trials were conducted at 10 sites around the state of Wisconsin and represent the North Central, Central, and Southern Regions of the State.  Detailed descriptions of the trials, variety traits, and other useful decision-making information can be found in the report.

Top 10 Yield Limiting Factors in Wisconsin Soybean

Wisconsin Soybean Pocket Guide

Wisconsin Soybean Pocket Guide

Making timely decisions during the crop season can be the key to maximizing yields.

These decisions include variety selection, planting date, when and which inputs to apply, calibrating planters for maximum yield; and managing seedling health, plant diseases, weeds, and other yield-robbing pests.

Click here to view the pdf