Skip to main content

Content by Connie Strunk

Left: Green soybean plants covered with yellow and brown spots indicative of frogeye leaf spot infection.  Right: Green soybean trifoliate that is covered in brown spots.

Deciding on Fungicide Application to Manage Mid-Late Season Soybean Leaf Fungal Diseases

Soybean leaf diseases can develop in some soybean fields to reach yield-reducing levels. The question that growers often ask is whether it is profitable to apply a fungicide to soybeans at the R3/R4 growth stage in South Dakota.

A mostly green corn leaf that is in brown to yellow markings caused by southern rust.

Is a Fungicide Applied at Tasseling Profitable in Corn?

Corn is currently at tasseling/silking across the state. This is usually the growth stage when a fungicide is applied to control fungal diseases.

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.

Three wheat plants exhibiting disease symptoms. From left: Tan spot, powdery mildew, and Barley yellow dwarf.

Winter Wheat Diseases Update: Fungal Diseases and Barley Yellow Dwarf Developing

Tan spot and powdery mildew as well as barley yellow dwarf were found developing at low levels in winter wheat fields scouted the week of May 24, 2020.

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

Wheat plants exhibiting symptoms of tan spot and powdery mildew.

Does Early Fungicide at Tillering Result in a Profitable Yield?

Tan spot and powdery mildew pathogens are two residue-borne pathogens that can infect wheat early in the season. These diseases can lead to poor tillering, and their continued development can lead to yield loss.

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.

A corn field with several plants showing symptoms of stalk rot.

Assess for Corn Stalk Rots

Several corn fields are beginning to show stalk rot and top dieback symptoms. Stalk rots cause the entire plant to die prematurely, which can lead to plants lodging under windy conditions making harvesting problematic.

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.