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Soybean Diseases

All Soybean Diseases Content

Green soybean plant with white mold present on the stem and pod.

Start of Flowering Is the Ideal Time for White Mold Management in Soybeans

Some early planted soybeans are starting to flower (R1 growth stage). One soybean disease that needs to be managed at this growth stage is white mold.

A soybean root with several small white cysts growing on it.

Soybean Cyst Nematode in South Dakota: History, Biology, and Management

Factsheet about Soybean Cyst Nematode history, biology and management in South Dakota

soybean pods

2019 Soybean Fungicide Field Trials Summary

This document contains results of soybean field trials conducted during the 2019 growing season to evaluate foliar fungicides to manage various soybean diseases.

An aerial view of a soybean field with noticable rows of yellowing plants due to SCN infection.

Early Yellowing in a Soybean Field May Indicate Presence of the Soybean Cyst Nematode

Some portions of soybean fields may show clusters of plants yellowing while the rest of the field is still green. One of the factors that could lead to soybean plants showing early yellowing in clusters is soybean cyst nematode (SCN).

Soybean plant with with yellow-chlorotic blotches between leaf veins and noticable browning due to sudden death syndrome.

Sudden Death Syndrome Starting to Develop in Soybeans

Sudden death syndrome of soybean is starting to develop in soybean fields in South Dakota. Fields currently being found with sudden death syndrome have symptomatic plants scattered within the field, but continued disease development may lead to larger clusters of infected plants.

Soybean leaves with small, white lesions with red-to-purple halos throughout.

Frogeye Leaf Spot Developing in Soybeans

Frogeye leaf spot, also known as Cercospora leaf spot, was found in several soybean fields scouted the week of August 19, 2019. Frogeye leaf spot is characterized by irregular to circular lesions, which are tan-to-gray in color with reddish-purplish borders.

A producer loading a planter with fungicide-treated soybean seeds.

Pre-Plant Disease Management Considerations

If the forecast holds true, it looks like it is going to be another year of excessive soil moisture and possible flooding come this spring. The increased level of soil moisture has implications with regards to plant stand establishment as well as root rot and nematode infestations.

Soybean leaves with several bright green lesions progressing into tears with brown crusting along the edges.

Bacterial Blight Common in Soybean Fields

Several soybean fields scouted the week of July 15, 2019 were found with bacterial blight developing. The frequent rains experienced in most soybean growing counties have led to the development of this disease. Bacterial blight affected leaves are most evident on younger leaves in the upper canopy.

A green soybean plant with purple and white flowers begining to develop.

Current Weather Conditions Are Conducive White Mold Development in Soybeans

Frequent rains and overcast conditions continue to occur in South Dakota’s main soybean growing counties. These conditions favor white mold development. In some of these counties, soybean is already at R1, which is also the best timing for fungicide application targeting white mold control.

A green soybean pod with frogeye leaf spot symptoms. The pod is partially open to reveal developing seed at the end of the pod with frogeye leaf spot symptoms developing.

Frogeye Leaf Spot of Soybean

This fact sheet is about a soybean disease that is increasingly becoming more severe in South Dakota. Moreover, fungicide resistance for this pathogen has been detected in South Dakota.