Black and Other Cutworm Species in Minnesota Corn

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Black cutworms are not the only cutworm species than can injure crops in Minnesota. As corn (and other row crops) germinate and begin to emerge they can be attacked by several species of cutworms. Table 1 lists some of the most common species that might be found in Minnesota corn fields. Most species can overwinter in Minnesota as eggs or larvae. Black and variegated cutworms cannot winter here and migrate into the state each spring.

While we can project cutting dates for the black cutworm, corn should be scouted for other cutworm species as soon as it emerges. Because cutworms that overwinter, particularly those that winter as larvae, begin development before migrant black cutworms arrive, they are ready to feed on corn early. Often, the first corn leaf feeding observed in the spring is from overwintered dingy cutworm larvae.  

Species
Eggs Laid
# of Generations
Overwinters as
Likely habitat

Black

Spring-Summer

3

Adults migrate

Late-tilled fields, early broadleaves

Bronzed

Fall

1

Eggs/larvae

After sod

Clay-backed

Fall

1

Larvae

After sod

Darksided

Fall

1

Eggs

Dingy

Summer-Fall

1

Larvae

After sod and alfalfa, weedy fields

Glassy

Summer-Fall

1

Larvae

After sod

Redbacked

Fall

1

Eggs

Light/medium textrued soils

Sandhill

Summer-Fall

1

Larvae

Sandy soils

Variegated

Spring-Summer

2

Adults migrate

After alfalfa, weeds

Certain species prefer particular habitats. For example, sandhill cutworms are found in sandy soils and several species tend to be problems in crops planted into sod. Dingy cutworms are often abundant when corn is planted after alfalfa or fields that were weedy the previous year. 

Species ID is important to determine damage potential. Small larvae of all species feed on weeds and leaves and cannot cut corn. Dingy and variegated cutworms are primarily leaf feeders feeding at or above the soil surface. Consequently, they don’t usually cut corn below the soil line and growing point and the plant recovers. However, the larvae of some species like glassy, sandhill and black cutworms tend to feed below ground at or below the growing point.

This tendency for feeding to kill corn plants makes black cutworm a threat. When larger larvae tunnel into the growing point, corn as large as 5 or 6 leaves can be killed. Fortunately, damaging black cutworm populations are infrequently encountered.

Pictures of some of these cutworm species can be found at Northern Plains IPM: Cutworms on corn . Some excellent comparison images of black and dingy cutworms are available at the University of Nebraska NebGuide: Corn cutworms. With a bit of practice, the two species are easily distinguished by the size of paired black bumps (tubercles) on the top of each segment.  These tubercles are unequal in size on the black cutworm.

Look at the tubercles on the cutworm picture below; the small black bumps on each segment near the back of the cutworm. The unequal size is a characteristic of black cutworms.   The overall appearance of black cutworm larvae is black and "greasy". Under a good hand lens, the skin of the black cutworm has a granular appearance.

Black cutworm