Corn Earworm (Helicoverpa zea) 

CEW is a pest that attacks many different crops, including tomato, hemp, tobacco, cotton, soybean and corn. In the southern United States, the damage from CEW is more severe due to the warmer climate and its ability to over winter. In the north it typically does not over winter. Migrating adults arrive in the northeast between mid-July and late August, and can produce between one and two generations. Adult moths will lay their eggs on fresh corn silk. Upon hatching, the larvae will feed on corn silks before entering the ear to feed on the kernels, reducing yield and appearance of the cob. In uncontrolled areas, heavy infestations can cause almost 100% of the ears to be infested.

Life cycle of Corn Earworm

• Adult moths lay eggs on warm, moist and cloudy evenings at dusk. Eggs will hatch between 2 and 10 days depending on the temperature.
• Young larvae move down the silk channel and enter the ear where they feed on developing kernels. Here the larvae eat the kernels down to the cob and leave excrement (frass) near the tip of the ear.
• Once fully developed, the larvae will leave or fall off the corn ears to the ground. They then burrow 3 to 5 inches (76 to 127 mm) into the ground to pupate for 10 to 25 days depending on the temperature.
• After pupation, moths will emerge from the ground. The total development cycle of CEW from egg to adult takes about 30 days during the summer.
• In New York State, CEW larvae do not typically overwinter; however, overwintering is becoming more common in certain areas. With ongoing climate change, these areas appear to be expanding.
• CEW flights in New York State usually begin in mid-July and continue through September, but in overwintering locations, adult CEW have been detected as early as late May. 

Management of Corn Earworm

Pest monitoring

• Scouting for eggs and CEW damage is very difficult. CEW eggs are very small and laid individually, and the larvae enter and feed on corn ears with little external damage.
• It is better to rely on pheromone or black light traps to monitor CEW populations. Spray intervals for CEW can be based off of weekly trap catches.
• For more information on monitoring CEW, see the Cornell Pheromone Traps for Sweet Corn fact sheet.
• For more instruction on sweet corn trap monitoring, watch Cornell IPM’s Sweet Corn Pheromone Trap Network Setup and Monitoring video.
• The Sweet Corn Pheromone Trapping Network has been monitoring CEW populations in NY since 1997. To get weekly trapping reports visit the IPM sweet corn network website. 

Control

• Cultural control: Planting early in the season can help avoid most of the damage from CEW. If sweet corn is harvested before mid-August, it will suffer from little to no damage.
• Biological control: Certain species of insects, such as the big-eyed bug, parasitic flies and Trichogramma wasps will feed on or parasitize corn earworm eggs and larvae. For more information, see the Trichogramma ostriniae wasp fact sheet on the Cornell IPM website.
• Bt corn hybrids: Certain field and sweet corn hybrids are available that possess resistance to CEW. These hybrids contain the Bt trait, which enables the plant to produce insecticidal proteins that help protect against CEW feeding. Refer to seed company guidelines when using Bt or other corn hybrids.
• Chemical control: Refer to your local Cornell Cooperative Extension or state guidelines when applying insecticides to crops.
  • Responsible pesticide application should be planned when applying any insecticide to crops. This should be done to ensure that resistance to pesticides is minimized in the targeted pest population, while minimizing damage to beneficial insects and pollinator populations.
  • Use the EIQ (Environmental Impact Quotient) calculator to access the environmental and health impacts different pesticides have before selection.