One Million cutworm caterpillars #763146 - Ask Extension


One Million cutworm caterpillars #763146

Asked July 21, 2021, 9:02 PM EDT

There are about one million caterpillars making their way across and down a tar road. They are coming out of a corn field and headed towards about 10 houses on the north shore of Waverly Lake. I used inaturalist to identify them as bronzed cutworm moths. A neighbor said this has happened for several days. Another neighbor was upset and disturbed. My questions are: What is happening? Is this a problem?

Wright County Minnesota

Expert Response

Bronzed cutworm caterpillars (Nephelodes minians Guenee) are native to Minnesota and overwinter as eggs in weedy or grassy areas. They are nocturnal and usually hide during the day. Fully grown larvae are slightly larger than 1 1/2 to 2 inches long. The huge number of the bronzed cutworm near your yard can result in lawn injury. Cutworms usually dig a burrow in the ground. At night they emerge and clip off grass blades. This feeding damage appears as circular spots of dead grass or sunken spots. Turf grass is normally able to outgrow bronzed cutworm activity, unless it is already stressed by drought. It is possible that the current dry conditions could prevent the lawns from recovering from the feeding if the turf is not watered. Examples of common pesticides effective against cutworms are carbaryl, cyfluthrin and permethrin.

Pat Mack Replied July 21, 2021, 11:21 PM EDT

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