Content by Patrick Wagner

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.

Alfalfa weevil larvae and adult.

Alfalfa Weevils Are Active in Some Parts of South Dakota

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

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

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.

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.

Four common South Dakota ticks: American dog, Rocky Mountain wood, blacklegged and Lonestar.

Spring is here, and so are the ticks!

As spring continues to bloom, more arthropods will begin to emerge from winter dormancy. Ticks are among the first to appear, and statewide reports have already been flowing in.

Bottom side of a soybean leaf revealing a sever soybean aphid infestation.

Management Recommendations for Soybean Aphids

In many fields across eastern South Dakota soybean aphid populations have reached economic thresholds, and there have been a lot of questions regarding the best approach to managing the 2024 outbreak.

Light colored moth on a yellow sunflower head.

Sunflower Moths Observed in South Dakota

Sunflower moths have been observed in South Dakota sunflower fields this week. Sunflower heads are most susceptible to damage caused by the sunflower moth caterpillars from the onset of flowering to when the ray petals begin drying.

Small, green teardrop shaped insects on a green, soybean stem with pink flower.

It’s Time to Scout for Soybean Aphids

Small populations of soybean aphids were observed this week while scouting. Early scouting will ensure that populations do not rapidly increase and exceed the recommended economic threshold.