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Insect & Pests

All Insect & Pests Content

A small black bug with tan margins on the wings. This insect is resting on a blade of grass that is green with white spots.

Black Grass Bug Activity Expected in Coming Weeks

Spring green-up is the time to be watching for black grass bug activity. Large populations of this early-season pest can cause severe damage to pasture (up to 90% forage reduction) and infest the edges of wheat fields.

Dark colored caterpillar feeding on wheat head.

Scout for True Armyworms in Oats and Wheat

During most years, we start worrying about true armyworm activity in wheat fields in mid-July. However, the strong southerly winds that we experienced during the last two weeks pushed several insect pests north ahead of their normal schedule

Left: Brown moth with light markings present on a green leaf. Right: Brown moth with light markings present.

Army Cutworm Moths Among the Recently Reported Western Bean Cutworm Moths

Last week, we published an article about the presence of western bean cutworm moths being very abundant throughout Central and Western South Dakota. However, when talking with an entomologist from a neighboring state, they suggested the moths could also be army cutworm moths.

Green wheat stems with a gray slug feeding on them.

Slugs Causing Issues in Some South Dakota Wheat Fields

Slug activity in wheat fields has been reported in South Dakota. Although slugs are not normally an issue in South Dakota crops, they can pose a threat when field conditions are just right.

Top: Tan caterpillar with dark brown head on corn stalk. Bottom: Black caterpillar with light stripes and yellow-brown head capsule. Caterpillar also has small spines on body segments.

Caterpillars Active in South Dakota Corn Fields

Both European corn borer (Ostrinia nubilalis) and corn earworm (Helicoverpa zea) are active in corn fields. Sometimes the caterpillar activity and identity of these two species can be confused.

Two common caterpillar pests of corn. Top: Corn earworm caterpillar. Bottom: European corn borer.

A Case of Mistaken Caterpillar Identity

Tweets about European corn borer (Ostrinia nubilalis) caterpillars in the stems of conventional corn and feeding in the whorls of corn are crossing my Twitter feed. Unfortunately, there is a problem with some of these tweets. Not all of the caterpillars that are being identified as European corn borer caterpillars are actually European corn borer caterpillars!

Young corn plant with three circular feeding holes in a leaf.

Black Cutworm Caterpillars Are Actively Feeding in South Dakota

We received numerous reports this week of small holes in V1-V2 corn plants. The holes are the result of early instar cutworm caterpillar feeding and, more specifically, black cutworm caterpillars. After hatching, black cutworm caterpillars initially feed on the leaves. As they develop and become larger, they pose a clipping or cutting threat to corn.

A shiny caterpillar with a light brown head, dark brown body, and three yellow stripes down the length of its back.

Watch Corn for Bronzed Cutworm Activity

Bronzed cutworms are not a common pest of corn in South Dakota. However, they can become an issue when corn is planted into areas that were previously grassland. Like its name implies, bronze cutworms feed on corn above the soil surface, which often results in cutting or clipping.

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

Monitor Newly Emerged Corn for Black Cutworm Activity

There are several important insect pests that can severely injure corn during the early vegetative stages. One of these pests is the black cutworm. Although black cutworm caterpillars injure corn by feeding on leaf tissue, the serious damage occurs when caterpillar feeding results in the cutting of young corn plants.

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

How to Identify Common Stalk Borers and Thresholds

As corn is being planted, it is important to remember that there are insect pests capable of injuring young, vegetative corn. One such pest is the common stalk borer. Although common stalk borer outbreaks are sporadic, when present in high numbers they can cause significant yield loss.