Content by Philip Rozeboom

Green alfalfa weevil larvae with a white stripe running down its body.

Alfalfa Weevil Activity Prediction Update: May 29, 2025

The lowest calculated degree days in South Dakota indicate that fourth instar larvae should be active, while the highest calculated degree days suggest that pupation is occurring in the field.

A yellow beetle with a black head, and square black markings on its back standing on a soybean leaf.

South Dakota Overwintering Bean Leaf Beetle Predicted Mortality: 2024-2025

Each year we evaluate the overwintering success of bean leaf beetles in South Dakota. For adult bean leaf beetles that successfully overwintered, emergence will begin in the spring and they will move into soybean fields.

Two small, green soybean plants with brown to yellow coloration on their leaf edges, indicative of herbicide damage. Tan sand and yellow fertilizer pellets are in the background.

Wind and Rain May Have Delayed Preemergence Herbicide Application: What Now?

With recent winds and rain, preemergence herbicide applications may be further delayed. Scouting to determine if crops and/or weeds have emerged is critical to ensure effective and safe application of preemergence herbicides.

Alfalfa Weevils Are Active in Some Parts of South Dakota

Degree day accumulations indicate that alfalfa weevil larvae should be active throughout South Dakota.

Alfalfa Weevil Activity Prediction Update: May 22, 2025

Degree day accumulations for alfalfa weevil larvae indicate that third to fourth instar larvae should be active in fields throughout South Dakota.

Corn plants and scattered weeds emerge from a dry, no-till field.

Dry Conditions May Hinder the Performance of Recently Applied Preemergence Herbicides

If a preemergence herbicide does not receive an activating rainfall, generally 0.5 to 1 inch of rain, many weeds will emerge, as the herbicide remains on the soil surface.

A green leafy spurge plant with small, yellow bracts at top. Various brown and green plants surround the green leafy spurge plant.

Leafy spurge has germinated and is growing rapidly in South Dakota: Scout carefully!

Leafy spurge can reduce the value and productivity of pasture and displace desirable vegetation. Now is the time to scout for infestations to determine which management tactics will be most effective.

Ten small green pots with brown dirt and green kochia plants within with a black background.

Saflufenacil-Resistant Kochia Confirmed in South Dakota

Saflufenacil is an herbicide that can be applied at a burndown timing before most South Dakota crops to effectively manage kochia. However, overreliance on saflufenacil has selected for resistant kochia in our region.

A small black bug with tan margins on its wings resting on a grass seed head.

Black Grass Bug Activity Ramping Up

Black grass bugs feed on fresh green growth, which can result in stunted plants and decreased forage quality. Monitoring and potential management of black grass bugs will be of increased importance this spring, especially if drought persists.

2025 Rangeland Grasshopper Hazard map. Photo Courtesy of USDA APHIS, PPQ. ALT TEXT: Map of South Dakota of Northern Great Plains and the Western United States. Colors indicate the number of grasshoppers per square yard in each of the sampled locations. For a detailed description, please call SDSU Extension at 605-688-4792.

South Dakota Grasshopper Prediction for 2025

In 2025, it is likely that grasshopper populations will once again reach levels capable of causing issues in some areas of the state. Scouting should begin shortly after planting in areas where they were problematic in 2024 and continue throughout the growing season.