Cutworms are the larvae of noctuid moths. These common moths are medium-sized with fairly dull coloration. The gray to tan caterpillars are hairless, nocturnal, and generally spotted, striped, or otherwise marked. They may be 1/4" to 1" in length and tend to curl up when disturbed. Cutworms feed by chewing leaves and buds, typically on lower portions of the tree. Symptoms of damage include ragged, irregularly chewed leaf margins and buds damaged prior to bloom. Fruit may also be damaged, with small to large holes chewed into the surface. Cutworms typically spend the day just beneath the soil surface or under debris near the host. While armyworms are typically day feeders, cutworms usually feed at night. It is advisable to search for them with a flashlight in the dark. Weeds are the primary food source for cutworms.

Management Options

Non-Chemical Management

Cut weeds and remove debris from around trees.
Encourage natural enemies of cutworms including birds and spiders.
Use a sticky material such as Tanglefoot or Stik-Em. It is applied to a polyethylene strip secured around the trunk and acts as a barrier to prevent access to the foliage. Keep in mind that low-hanging branches and tall weeds may also provide access.
Hand-pick night-feeding larvae, when practical.

Select non-chemical management options as your first choice!

Chemical Management

IMPORTANT: Visit Home and Garden Fact Sheets for more information on using pesticides

Apply when caterpillars are present. Bacillus thuringiensis (Bt) is only useful if larvae are feeding. Use a spreader-sticker with liquid Bt formulations. Do not apply Sevin (carbaryl) to flowers or allow to drift onto blooming plants. It is deadly to bees. Homeowners should not make foliar applications to trees over 10 ft tall. Consult a commercial pesticide applicator for treatment of trees and shrubs over 10 ft. tall.

Listed below are examples of pesticides that are legal in Washington. Always read and follow all label directions.

Bonide Thuricide BT Conc
Active ingredient: Bacillus thuringiensis subsp. kurstaki | EPA reg no: 4-226
Bull's-Eye Bioinsecticide
Active ingredient: spinosad (spinosyn A+D) | EPA reg no: 62719-314-56872
GardenTech Sevin Conc Bug Killer
Active ingredient: carbaryl | EPA reg no: 264-334-71004
Monterey Garden Insect Spray [Organic]
Active ingredient: spinosad (spinosyn A+D) | EPA reg no: 62719-314-54705
Naturalis L
Active ingredient: Beauveria bassiana | EPA reg no: 53871-9
Safer Brand BioNEEM Multi-Purpose Insecticide & Repellent Conc [Organic]
Active ingredient: azadirachtin | EPA reg no: 70051-6-42697
This list may not include all products registered for this use.

Images

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Caption: Spotted cutworm Photo by: K. Grey
Caption: Bertha armyworm Photo by: K. Grey
Caption: Cutworm eggs Photo by: A.L. Antonelli
Caption: Western yellow stripe armyworm adult Photo by: A.L. Antonelli

WSU Extension

Hortsense