Apple: Cutworms and armyworms

Biology

Cutworms and armyworms are the larvae of noctuid moths. These common moths are typically 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 and armyworms 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. While armyworms typically feed during the day, cutworms spend the day just beneath the soil surface or under debris near the host. They usually feed at night, so it is advisable to search for them with a flashlight in the dark. Weeds are the primary food source for cutworms.

Management Options

Use Integrated Pest Management (IPM) for successful plant problem management.

Non-chemical Management

Select non-chemical management options as your first choice!

• Cut weeds and remove debris from around trees.
• 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.
• Encourage natural enemies of cutworms including birds and spiders.

Chemical Management

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

• Certain biological insecticides, such as spinosad and Bacillus thuringiensis (Bt), will work on these pests.
• Use spinosad only at night to protect bees.
• Bt formulations are effective only if caterpillars are actively feeding.
• Use a spreader-sticker with liquid Bt formulations.
• 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.

Approved Pesticides

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

• Bonide Captain Jack's Deadbug Brew R-T-U [Organic]
  Active ingredient: spinosad (spinosyn A+D) [EPA registration number: 4-472]
• Bonide Thuricide BT Concentrate
  Active ingredient: Bacillus thuringiensis subsp. kurstaki [EPA registration number: 4-226]
• Natural Guard Spinosad Bagworm, Tent Caterpillar & Chewing Insect Control
  Active ingredient: spinosad (spinosyn A+D) [EPA registration number: 62719-314-7401]
• This list may not include all products registered for this use.

Additional Images