WSU Extension

Hortsense

Corn
 
Disease
Root, stalk, and ear rots 
Seed rot and seedling blight (damping-off) 
Smut 
Insect
Brown marmorated stink bug 
Corn aphids 
Corn earworm 
Cutworms and armyworms 
Earwigs 
Spider mites 
Western spotted cucumber beetle 



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Caption: Bertha armyworm
Photo by: K. Grey
  
Corn : Cutworms and armyworms
(revision date: 5/11/2015)


Biology
Cutworms and armyworms are the larvae of noctuid moths. These common moths are medium-sized with fairly dull coloration. The greenish, grayish, or 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 may feed by cutting through stems of young plants an inch or less above ground level. Several plants may be damaged in one night. 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 their primary food source.
Management Options

Non-Chemical Management
  • Control weeds and grasses in and near the garden.
  • Remove debris that may provide shelter for cutworms.
  • Hand-pick night-feeding larvae, when practical. Scratch soil at base of damaged plants to find larvae in the daytime.
  • Encourage natural enemies of cutworms including birds and spiders.
  • 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 barrier may help prevent cutworm attack.
Select non-chemical management options as your first choice!

Chemical Management

Bacillus thuringiensis will provide some control if caterpillars eat enough of it. Use a spreader-sticker with liquid Bt formulations. Apply other materials to the soil surface if cutworm damage is observed.

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 reg no: 4-472
  • Bull's-Eye Bioinsecticide
    Active ingredient: spinosad (spinosyn A+D)  |  EPA reg no: 62719-314-56872
  • Safer Brand BioNEEM Multi-Purpose Insecticide & Repellent Conc [Organic]
    Active ingredient: azadirachtin  |  EPA reg no: 70051-6-42697
  • Safer Brand Garden Dust RTU [Organic]
    Active ingredient: Bacillus thuringiensis subsp. kurstaki  |  EPA reg no: 36488-25-42697
  • Worryfree Brand Garden Insect Killer RTU
    Active ingredient: canola oil, pyrethrins  |  EPA reg no: 67702-6-33116
  • This list may not include all products registered for this use.
Images

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Caption: Bertha armyworm
Photo by: K. Grey
Caption: Spotted cutworm
Photo by: K. Grey