Black cutworm feeding damage being found in some southwest Michigan corn fields

Be on the lookout for black cutworm larvae in corn fields across southwest Michigan.

There have been reports of a few corn fields that have high numbers of cutworms in Van Buren County. I have seen evidence of clipping in a field in northern Cass County. Gary Blonde, gronomist with NorthStar Grain in Decatur, Mich., reported that the heaviest populations in a few impacted fields had several cutworm larvae per row foot. Watch for window pane feeding caused by small larvae, and plants that are clipped near the soil surface for more mature larvae.

Black cutworm damage tends to be sporadic in nature. Moths are often deposited in areas by thunderstorm events and damage occurs in fields where winter annual weeds or cover crops were present. MSU field crops entomologist Chris DiFonzo published an article about black cutworms in Michigan in 2011, including very good pictures.

Insecticides can be very effective in controlling this pest, but infestations need to be caught early to prevent unacceptable stand losses. MSU Extension Bulletin E-1582, Insect Control in Field and Forage Crops, will provide you with insecticide options, application rates and treatment thresholds. The standard threshold for treatment is 5 percent clipping damage and live larvae are present.

Cutworms are not the only pest that can remove plants. Canadian geese can also feed on the emerging corn plants. Be sure to look for clipped plants and to dig around the base of clipped plants to see if you can find cutworm larvae.

It might be worthwhile to look for signs of armyworm feeding when you are out in the fields. Armyworm poses the most serious threat to small grains. In corn fields, armyworm moths like to lay eggs in fields that had cereal cover crops or grass weed infestations. Grassy areas of fields that were burned down late or are adjacent to grassy areas are likely to be at the most risk. Armyworm feeding on young corn plants usually appears as ragged leaf margins. Severe damage is the removal of leaf tissue down to the midrib of the leaves.

We have been catching armyworm moths in pheromone traps in elevated numbers near wheat fields in many places across Michigan this spring. Early detection through scouting is really the best way to protect your fields from unexpected damage from these insect pests.

Curious if your Bt hybrid is effective at controlling black cutworms or armyworms? Review the Handy Bt Trait Table developed by DiFonzo and University of Wisconsin field crops entomologist Eileen Cullen.

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