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ISSUE 1   May 15, 2008


Cutworms have been reported in winter wheat in the southwestern region of North Dakota and central and western South Dakota, and in lentils in east central Montana. Most of the cutworm species being reported are Army cutworms and pale western cutworms. Maps of Army cutworm and pale western cutworm forecast can be found on the "Western Region Cutworm Risk Warning" website of Montana State University:


North Dakota is at low risk for army cutworm and at low to medium risk for pale western cutworm (see maps). The medium risk area for pale western cutworm is located in the northwestern corner of North Dakota.

Army Cutworm Moths map

Pale Western Cutworm Moth map

Army Cutworm Moth Counts 3/24/08 Pale Western Cutworm Moth Counts 3/24/08

Cutworms become active when soil temperatures are above 40F. With the statewide cool soil temperatures in May, cutworms will develop slower and this could result in a prolonged feeding period this year. Cutworms injury plants by chewing and/or cutting the plant in the early stages of crop development (seedling stage = most susceptible). Generally, cutworms destroy more of the plant then they eat. Their numbers vary greatly from year to year and when numerous may destroy 50-75% of a crop! Cutworms feed at night and hide in soil during the day. Since there are early and late season cutworms, feeding activity usually extends from May through the end of June.

The key to successful cutworm control is early detection and knowing your plant population. Field scouts should look for cut or wilted plants, and dig around underneath freshly cut plants to find cutworms in the soil. A flashlight at night can also be used to find the night-feeding cutworms. If the plant population is below recommended, few or no plants can be lost to cutworm feeding. The greater the plant population the more damage can be tolerated without economic yield loss. When spraying insecticides for cutworm control, applications should be made in the evening when cutworms are actively feeding. Wet soil conditions will also improve insecticide efficacy, as cutworm feed near the soil surface in these conditions.

Treatment threshold vary depending on the field crop:

Canola 1 per square foot
Small grains 4 to 5 cutworms per square foot
Corn 3 to 6% of the plants cut and small larvae less than 1-inch present
Soybeans / Dry beans 1 or more larvae per three feet of row or 20% of plants cut
Sunflower 1 per square foot or 25-30% of plants cut
Alfalfa 4 to 5 or more per square foot (new or thin stands only 2/sq ft)
Lentils 2 to 3 cutworms per square meter (Canada)
Peas 2 to 3 cutworms per square meter (Canada)

Please see "2008 North Dakota Field Crop Insect Management Guide" for list of insecticides available on different field crops.



Two different formulations of Mustang Max (FMC Corporation) have been issued a 24(c) registration for control of various insect pests in sugarbeets in North Dakota this year.

1) Mustang Max: The expiration date for SLN ND-030003 (previously issued) has been extended to allow the use of Mustang Max insecticide (EPA Reg. No. 279-3249) until to March 17, 2013. This registration allows use of Mustang Max insecticide on sugarbeets at plant for control of wireworms, white grubs, cutworms, and as a foliar application for control of cutworms, flea beetles and grasshoppers.

2) Mustang Max EC: SLN ND-0800001 was also issued to allow use of the new formulation of Mustang Max EC (EPA Reg. No. 279-3327) on sugarbeets at plant for control of wireworms, white grubs, cutworms, and as a foliar application for control of cutworms, flea beetles and grasshoppers. Expires December 31, 2013.

The pesticide SLN labels are posted on the NDSU Entomology Extension Resources website:


Note: Due to concerns with potential negative impacts to the pallid sturgeon in Williams and McKenzie Counties by the US FWS, these products may not be used on sugarbeets grown under flood irrigation in these two counties.

(Source: J. Gray, ND Department of Agriculture)

Janet Knodel
Extension Entomologist

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