Raspberry: Cutworms and armyworms

categories: Raspberry Raspberry Insects Small Fruits

last review date: 2025-11-12 01:34

Biology

Cutworms and armyworms are the larvae of noctuid moths. These common moths are medium-sized with fairly dull coloration.

The pale green to brownish caterpillar 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. They climb into the plant and feed on buds, shoots, and foliage.

Armyworm behavior is similar to that of cutworms, but armyworms feed in large groups instead of individually. They tend to be voracious feeders.

The caterpillars typically spend the day just beneath the soil surface or under debris near the host. While armyworms oftentimes feed during the day, cutworms usually feed at night, so it is advisable to search for them with a flashlight in the dark.

Weeds are a primary food source for both cutworms and armyworms.

Management Options

See "Using Integrated Pest Management (IPM) in the Landscape" for successful problem management techniques.

Non-chemical Management

Select non-chemical management options as your first choice!

• Control weeds and grasses in and near the garden.
• Remove debris around plants that provides shelter for cutworms.
• Hand-pick night-feeding larvae, when practical. Scratch soil at the base of damaged plants to find larvae in the daytime.
• Encourage natural enemies of cutworms and armyworms including birds, spiders, and predacious insects. Avoid use of broad-spectrum insecticides that kill beneficial insects.
• Plastic or cardboard collars extending 2″ into the soil and 2″ above the soil can be placed around individual plants or groups of plants. The barriers may help prevent attack.

Chemical Management

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

• Apply Bacillus thuringiensis (Bt) products when first tiny worms or their damage are seen.
• Repeat Bt products applications at weekly intervals until threat subsides.
• Use a spreader-sticker with liquid Bt formulations.

Approved Pesticides

Examples of pesticides that are legal for home use in Washington State are listed below.
The list may not include all products registered for this use.

• Bonide Captain Jack's Deadbug Brew R-T-U [Organic]
  Active ingredient: spinosad (spinosyn A+D) (EPA reg. 4-472)
• Bonide Thuricide BT Concentrate
  Active ingredient: Bacillus thuringiensis subsp. kurstaki (EPA reg. 4-226)
• Bug Buster-O [Organic]
  Active ingredient: pyrethrins (EPA reg. 1021-1771-54705)