Corn earworm (Helicoverpa zea) is a type of caterpillar that feeds on corn ears, causing significant damage to kernels. Infestations can result in yield losses of up to 30%, making corn earworm a formidable threat.

But with proactive scouting strategies and quick action with chemical treatments like Willowood Lambda-Cy 1EC and GCS Bifenthrin 2EC, control is achievable.

(Image Credit: Ward Upham, Kansas State University, Bugwood.org)


How Does Corn Earworm Affect Corn Crops?

Corn earworm larvae have a voracious appetite for corn kernels, directly impacting the development of the ears and creating entry points for secondary infections. Severe infestations can even extend beyond the ears to the stalks and tassels, further compromising overall plant health and productivity.

Identifying Corn Earworm

Adult corn earworm moths have a wingspan of about 1.5 inches and can vary in color.

However, it is the larval stage that causes the most damage. These larvae are typically pale green or brown with longitudinal stripes along their body.

To identify the presence of corn earworm:

  • Closely inspect the silks, husks and kernels for signs of larvae or feeding damage

  • Look for chewed silks, holes in the husks and kernels, and the presence of frass

  • Monitor for any signs of secondary infections, such as discoloration, mold or decay

(Image Credit: Ward Upham, Kansas State University, Bugwood.org)

Regions Typically Affected by Corn Earworm

Corn earworm is widespread across the United States, particularly in the southern and eastern parts of the country. However, it can also pose a problem in other regions, especially during periods of migration.

When Does Corn Earworm Affect Crops?

Corn earworm can be present in corn fields at any point during the growing season. Early-season infestations are often caused by overwintering populations, while late-season infestations result from migration.

(Image Credit: Eugene E. Nelson, Bugwood.org)

How to Chemically Manage Corn Earworm

Start with corn hybrids that contain above-ground Bt traits, such as Viptera™ or Agrisure® Viptera 3110.

When deciding whether to employ chemical products to control corn earworm, farmers should first assess the severity of the infestation and determine the economic threshold for treatment. Then, consider these crop protection products:

  • Asana® XL*: Apply the first application at or before silking. Then, apply subsequent applications every three to five days until silking is complete. Apply at 5.8-9.6 fl oz/A. 

  • Willowood Lambda-Cy 1EC*: Use for control before the larva bores into the ear. Apply it at a rate of 1.92-3.20 fl oz/A. 

  • GCS Bifenthrin 2EC*: Apply it just before silking at 2.1-6.4 fl oz/A.

Consider integrating other management practices alongside chemical control, such as crop rotation, biological control, and pheromone traps, to enhance effectiveness and reduce reliance on insecticides. Rotating between different modes of action helps prevent the development of resistance in corn earworm populations, ensuring long-term sustainable pest management.


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Viptera™ is a trademark of Syngenta Group Company.

Agrisure® is a registered trademark of Syngenta Group Company.

*Asana® XL is a restricted use pesticide.

Asana is a registered trademark of Valent U.S.A. Corporation.

*Willowood Lambda-Cy 1EC is a restricted use pesticide.

*GCS Bifenthrin 2EC is a restricted use pesticide.

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