Insect & Pests

All Insect & Pests Content

Adult red sunflower seed weevil on a sunflower leaf.

Malathion receives special local needs approval to treat red sunflower seed weevils in South Dakota from July 15 to August 31, 2025

The request was submitted and approved by the Environmental Protection Agency due to the large populations of red sunflower seed weevil present in South Dakota that are resistant to pyrethroid insecticides.

Green corn leaf with ragged holes through-out caused by common stalk borer feeding.

Start Scouting for Common Stalk Borer Activity

Enough degree days have accumulated in some areas of South Dakota for common stalk borer caterpillars to start moving to corn end rows.

Purple-brown caterpillar with orange head on a green corn leaf.

Common Stalk Borer Activity Estimate: June 5, 2025

In the southern counties of South Dakota, degree day estimates indicate that common stalk borer caterpillars are beginning to move from weedy hosts along field edges into corn fields.

Small black and yellow beetle feeding on the green leaf of a canola plant.

Start Scouting Canola for Flea Beetle Activity

There are three species of flea beetles that commonly infest canola and feed on the leaves. The main concern occurs early in the season when these beetles can rapidly defoliate the plants.

Dectes Stem Borer in Soybean Survey: 2023 and 2024 Results

During the 2023 and 2024 growing seasons, researchers at SDSU surveyed soybean in Eastern South Dakota for the presence of Dectes stem borer adults.

A small green corn plant that has been cut and is laying on the ground.

Scout Corn for Black Cutworm Activity

Black cutworms are a migratory moth that moves into South Dakota during early spring. Although black cutworm caterpillars cause minor corn injury by feeding on leaf tissue, serious injury occurs when feeding results in the cutting of young corn plants.

Plastic bag containing numerous green larvae.

Alfalfa Weevil Populations Rapidly Increasing in Western South Dakota and Starting to Show up in Eastern South Dakota This Week

Recent degree day accumulations for alfalfa weevils in western South Dakota would suggest that alfalfa weevil larvae activity should be wrapping up for the 2025 season. However, recent scouting of alfalfa suggests otherwise.