Corn Earworm Presence: Monitoring and Field Inspection Guide

Headshot of Trent Klarenbach, founder of Klarenbach Research
Trent Klarenbach
March 28, 2024
A farmer inspecting corn silks for earworm infestation.
April 11, 2024
Corn earworms, scientifically known as Helicoverpa zea, are a significant pest in agricultural settings, particularly in cornfields. Recognized for their detrimental impact on crop yields, these pests necessitate vigilant monitoring and management strategies to mitigate their effects.

Understanding Corn Earworm

Corn earworm larvae on a corn ear.

Biology and Behavior

Corn earworms are nocturnal moths that lay eggs on corn silk. The larvae, or caterpillars, are the primary concern for farmers, as they directly feed on the corn ears. These pests have a diverse diet, also affecting crops like tomatoes, cotton, and sorghum. Understanding their life cycle is crucial for effective pest management.

Seasonal Development

The lifecycle of corn earworms includes overwintering in the soil as pupae, emerging as adults in spring, and then laying eggs on corn plants. The number of generations per year can vary geographically, with warmer regions experiencing more cycles due to favorable conditions.

Monitoring Techniques

A blacklight trap in a cornfield capturing corn earworm moths.

Visual Inspection and Trapping

Monitoring for corn earworms involves regular field inspections and the use of traps. Blacklight traps and pheromone traps are common tools used to monitor adult populations. The placement of traps and timing of inspections are critical for accurate monitoring.

Damage Identification

Farmers should inspect for direct damage to corn ears, as well as secondary signs like frass (insect waste) around the feeding areas. Early detection is key to preventing significant crop loss.

Control Strategies

Cultural Practices

Selecting corn varieties that are less susceptible to earworm infestation, such as those with tight-fitting husks, can reduce damage. Planting timing is also a strategic factor; early or mid-season planting can result in lower earworm pressure.

Different corn varieties in a field, illustrating varietal resistance.

Chemical and Biological Controls

Insecticides are commonly used to manage earworm populations, but resistance and environmental impacts must be considered. Biological controls, including natural predators and biopesticides, offer sustainable alternatives to chemical methods.

A farmer applying insecticide in a corn field.

Integrated Pest Management (IPM)

IPM approaches combine monitoring, cultural practices, biological controls, and chemical interventions to manage earworm populations effectively. This strategy emphasizes sustainable and environmentally friendly practices.

Effective management of corn earworms requires a comprehensive understanding of their biology, regular monitoring, and the strategic application of control measures. By integrating various management strategies, farmers can protect their crops from this pervasive pest and ensure higher yields.

For more detailed guidance and specific techniques, accessing resources from agricultural extension services like NC State Extension​ (NCSU Corn)​, Penn State Extension​ (Penn State Extension)​, and the University of Kentucky College of Entomology​ (University of Kentucky Entomology)​ can provide invaluable support to farmers dealing with corn earworm challenges.