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Monitor Lawns and Gardens for Bronzed Cutworm Activity

Brown caterpillar with tan head capsule and 3, light-tan stripes running along its back.
Figure 1. Bronzed cutworm caterpillar. Courtesy: Whitney Cranshaw, Colorado State University, Bugwood.org.

Bronzed cutworms can be an issue for lawns and gardens in South Dakota. In grass, bronzed cutworms will feed and leave small brown circular patches. Large populations of bronzed cutworm can result in severe lawn injury. However, grass is normally able to outgrow bronzed cutworm activity unless it is already stressed. In gardens, bronzed cutworms can cause serious injury to young plants. As their name implies, bronzed cutworms are capable of clipping and killing young plants. Bronzed cutworms have a single generation each year and are currently active as caterpillars in South Dakota.

Identification

Bronzed cutworm caterpillars are dark brown with a bronze sheen. These caterpillars have three yellow stripes that run the length of the bodies (Figure 1). Bronzed cutworm caterpillars have three pairs of true legs and four pairs of abdominal prolegs. When fully mature, caterpillars are approximately 1.5-1.75 inches in length.

Scouting

Scouting for bronzed cutworm is difficult because caterpillars are nocturnal and hide during the day. Therefore, scouting involves monitoring lawns for small brown spots and checking garden plants for signs of feeding injury on the leaves, wilted plants, or plants cut off near the soil surface.

Management

If bronzed cutworms are active in a garden, plants can be protected by placing aluminum foil or cardboard rings around the stems of young plants. This will prevent cutworm feeding and protect the plants. The foil or cardboard should be positioned 1-2 inches belowground and extend above the soil 2-3 inches. Repurposed paper towel tubes can be cut down and used as plant collars. Insecticide management for bronzed cutworms is difficult because they are nocturnal.

Related Topics

Garden & Yard Issues, Lawn, Plant