Corn earworms, or bollworms, feed directly on developing kernels. Large caterpillars may be green, brown or yellow with a pale brown or orange head. Corn earworms have light and dark stripes running the length of their body and four pairs of abdominal prolegs.

 

Sampling: During whorl stages, corn fields should be checked at least weekly until the crop is mature to determine the presence of insect pests or their damage. Sample 10 plants in 10 locations on a weekly basis for signs of tattered and torn whorls. Fewer plants can be sampled depending on pest density. To check for live corn earworm larvae, cut open at least two (or more) plants in each sample and record the number of larvae.

Pheromone (sex-attractant) traps are also used to monitor various insect flights, and can complement an effective scouting program. Traps can be used in each county or on individual farms to provide producers with advance warnings of insect infestations.

 

Treatment Thresholds: Whorl stage plants: Controls should be initiated when 75 percent of whorls have larvae present. Control of larvae in ears is not economically practical in field corn.

Management options

Insecticide (Trade Names) for CORN EARWORMLb Active Ingredient per AcreAmount Formulation per AcrePerformance Rating
bifenthrin (Brigade 2E, Discipline 2E, Fanfare 2E)0.063 - 0.14 - 6.4 oz6
carbaryl (Sevin XLR Plus 4)1 - 232 - 64 oz4
chlorantraniliprole (Prevathon 0.43 SC)0.05 - 0.0714 - 20 oz9
chlorantraniliprole, λ-cyhalothrin (Besiege)See label6 - 10 oz9
esfenvalerate (Asana XL 0.66E)0.03 - 0.055.8 - 9.6 oz6
methomyl (Lannate LV 2.4)*0.225 - 0.312 - 16 oz7
permethrin (Pounce 3.2E)0.1 - 0.24 - 8 oz5
spinetoram (Radiant SC 1)0.023 - 0.053 - 6 oz7?
spinosad (Blackhawk 36% WDG)0.05 - 0.072.2 - 3.3 oz7
β-cyfluthrin (Baythroid XL 1)0.0125 - 0.021.6 - 2.8 oz6
γ-cyhalothrin (Declare 1.25)0.008 - 0.01250.77 - 1.28 oz6
λ-cyhalothrin (Karate 2.08, Warrior II)0.016 - 0.0260.96 - 1.6 oz6
Z-cypermethrin (Mustang Max 0.8E)0.0125 - 0.0252 - 4 oz6
  • Planting in the recommended planting window is suggested to avoid late-season infestations of caterpillar pests.
  • Certain Bt corn technologies are effective at controlling corn earworms in whorls or in corn ears.