Corn Earworm | Pioneer® Seeds

Key Points

  • Corn earworm is a pest of field corn, sweet corn and several other crops throughout much of North America.
  • Populations do not usually overwinter in most of the Corn Belt and must re-infest each year.
  • Corn earworms are cannibalistic and normally only one will be found per ear.

Pest Facts and Impact on Crop

  • Latin Name: Heliothiszea
  • Closely related or indistinguishable from:
    • Cotton bollworm: Helicoverpa armigera
    • Tobacco budworm: Heliothisvirescens, etc.
  • Importance
    • Grain losses estimated at 2.5% annually
    • Losses in southeastern U.S. as high as 16.7%
    • Losses in sweet corn as high as 50% in unsalable produce
  • Found worldwide but does not usually overwinter in most of the Corn Belt and must re-infest each year
  • Large range of hosts including corn, cotton, tobacco, tomatoes and other fleshy fruits and vegetables
  • In addition to the ear, occasionally larvae can be found in the whorl and foliage on younger plants

Photo - corn earworm larva

Pest Symptoms/Injury ID

  • Corn earworms are cannibalistic and normally only one will be found per ear.

Photos - Side by side - corn ear tips damaged from insect feedingI

  • They will frequently be near the tip but may feed down the ear creating a track of damaged kernels.
  • The injury creates an ideal environment for ear fungi to invade and may lead to quality problems at harvest.

Photo - damage to corn ear from insect feeding

Distribution

Pest ID:

  • Similar species
    • Note the lack of straight lateral lines or large tubercles on the sides of the western bean cutworm
    • Contrast with the thin white line of the fall armyworm
    • Contrast with the wider line of the corn earworm
  • Corn earworms are found in many colors
    Photos - Side by side - Identification - Brown Marmorated Stink Bug and Brown Stink Bug

    Western bean cutworm

    Photos - Side by side - Identification - Brown Marmorated Stink Bug and Brown Stink Bug

    Fall armyworm

    Photos - Side by side - Identification - Brown Marmorated Stink Bug and Brown Stink Bug

    Corn earworm

IPM Practices

  • Trapping
    • Light traps or pheromone traps can indicate when adults are flying.
  • Scouting
    • Scouting can be done in the field by looking for eggs on the green silks and turning back the silks at the tip of the ear to look for larvae.
  • Management timing
    • Because the larva is exposed outside the ear for only a short time, economical timing of insecticides is difficult.
    • Stop application after silks turn brown.
  • Resistance available
    • Tight husks give some protection, but real resistance is only available with Bt hybrids.
  • Pesticide use
    • In field corn, insecticide use is rarely warranted.
    • Please check local accepted practices and label instructions when growing either sweet corn, seed corn, or another specialty crop.

Management Considerations

  • Favorable conditions
    • Warm humid nights.
  • Natural enemies
    • Predators include birds, big-eyed bugs, lady beetles, and minute pirate bugs.
    • Trichogramma parasites infest some eggs, but control is minimal.
  • Pioneer® brand corn with Optimum® Leptra® insect protection provides strong above-ground insect control with a superior level of efficacy against ear-feeding pests for cleaner ears and improved grain quality.
    • These products provide protection against a broad spectrum of pests, including corn earworm, European corn borer, southwestern corn borer, fall armyworm, black cutworm and western bean cutworm.
    • Each product contains 95 percent of a Pioneer brand hybrid with three modes of above-ground insect protection, blended with 5 percent in-the-bag refuge of a similar non-Bt hybrid with herbicide tolerance.
    • A 20 percent separate structured refuge is required in EPA-designated cotton counties.

Illustration - Corn earworm life cycle

Click here or on the above image for a larger view



The foregoing is provided for informational use only. Please contact your Pioneer sales professional for information and suggestions specific to your operation. Product performance is variable and depends on many factors such as moisture and heat stress, soil type, management practices and environmental stress as well as disease and pest pressures. Individual results may vary. Pioneer® brand products are provided subject to the terms and conditions of purchase which are part of the labeling and purchase documents.

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Agrisure Viptera® is a registered trademark of, and used under license from, a Syngenta Group Company. Agrisure® technology incorporated into these seeds is commercialized under a license from Syngenta Crop Protection AG. Roundup Ready® is a registered trademark used under license from Monsanto Company. LibertyLink® and the Water Droplet Design are trademarks of BASF.