C
Species Profile

Corn Earworm

Helicoverpa zea

One moth, many crops-guard the silks
Stephanie Frey/Shutterstock.com

Corn Earworm Distribution

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Invasive Species
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Found in 56 locations

Corn earworm

At a Glance

Wild Species
Also Known As Tomato fruitworm, Cotton bollworm, American bollworm, Earworm, Bollworm, Sorghum earworm
Diet Herbivore
Activity Nocturnal+
Lifespan 45 years
Weight 0.00022 lbs
Status Not Evaluated
Did You Know?

Adult H. zea moths typically have a wingspan of ~32-45 mm (field guides/extension keys; e.g., Capinera, 2008).

Scientific Classification

A noctuid moth species best known for its caterpillar, the corn earworm, which feeds on reproductive structures of crops (ears, bolls, buds) and is a key agricultural pest.

Kingdom
Animalia
Phylum
Arthropoda
Class
Insecta
Order
Lepidoptera
Family
Noctuidae
Genus
Helicoverpa
Species
Helicoverpa zea

Distinguishing Features

  • Larvae (caterpillars) highly variable in color (green, brown, pinkish) with longitudinal striping; robust, smooth-bodied noctuid larva
  • Feeds commonly in corn ears (silks and kernels), but is highly polyphagous (many host plants)
  • Adult is a medium-sized moth; forewings often yellowish-brown to olive-tan with darker markings (field ID can be difficult vs. close relatives)

Physical Measurements

Weight
0 lbs (0 lbs – 0 lbs)
Top Speed
10 mph
About 16 km/h sustained

Appearance

Primary Colors
Green Brown Tan
Secondary Colors
Striped Cream Yellow Black Gray
Skin Type Cuticle varies by stage: larva smooth to slightly bumpy skin with sparse short bristles from small dark bumps; soft-bodied; pupa hard smooth reddish-brown cuticle in soil; adult has scaled wings and hairy/scaled thorax (Noctuidae).
Distinctive Features
  • Larval stage is a caterpillar (Lepidoptera: Noctuidae), not a true worm. It feeds mainly on reproductive plant parts—ears, silks, bolls, buds, and fruit—of crops like corn, cotton, tomato, sorghum, and legumes.
  • Mature larva is about 38 mm long; published sources report a range of roughly 32-45 mm (UF/IFAS Featured Creatures; Capinera 2001).
  • Head capsule usually brown; body bears multiple longitudinal stripes; color polymorphism ranges from green to tan, pinkish-tan, brown, to nearly black depending on host and instar (Capinera 2001; CABI).
  • Typical noctuid caterpillar body plan: 3 pairs of true thoracic legs + 4 pairs of abdominal prolegs (A3-A6) and an anal proleg; prolegs with crochets (hooklets) (general Lepidoptera morphology; UF/IFAS).
  • Eggs are hemispherical/dome-shaped with vertical ridges; approximately ~0.5-0.6 mm in diameter (values commonly reported ~0.5 mm) and laid singly on host surfaces (Capinera 2001; UF/IFAS).
  • Pupation occurs in the soil in an earthen cell; pupa smooth, reddish-brown, typically ~14-18 mm long (reported ranges often within ~14-20 mm) (Capinera 2001; CABI).
  • Adult moth wingspan commonly about 32-45 mm; forewings tan to brown with darker markings; hindwings pale with a distinct dark marginal band (UF/IFAS Featured Creatures; Capinera 2001).
  • Timing depends on temperature: eggs hatch in 2 to 4 days; larvae feed 2 to 3+ weeks; pupae 10 to 14 days in warm conditions but longer in cool/overwintering; multiple generations occur in warm regions.

Sexual Dimorphism

Sexual dimorphism is subtle and most evident in the adult moth stage rather than the larva. Males and females are similar in wing coloration/pattern, but differ in antennae and abdominal form related to reproduction (typical for many Noctuidae; species accounts commonly note close similarity).

♂
  • Adult male antennae are more noticeably pectinate/bipectinate (more 'feathery') for pheromone detection compared with females (common noctuid trait; used in Helicoverpa sexing).
  • Adult males often appear slightly slimmer in the abdomen compared with egg-laden females (general noctuid morphology).
♀
  • Adult female antennae are typically more filiform (less pectinate) than males (common noctuid trait).
  • Adult females often have a fuller, broader abdomen when gravid (egg-carrying), aiding visual sexing in hand specimens (general noctuid morphology).

Did You Know?

Adult H. zea moths typically have a wingspan of ~32-45 mm (field guides/extension keys; e.g., Capinera, 2008).

A full-grown caterpillar reaches about 25-40 mm long before pupating in the soil (Capinera, 2008).

Females can lay hundreds to over 1,000 eggs in a lifetime; lab/field reports commonly cite ~500-1,500+ eggs per female depending on conditions (Hardwick, 1965; Capinera, 2008).

Eggs are tiny (about ~0.5-0.6 mm diameter) and are usually laid singly on fresh plant growth, often near corn silks or flower buds (Capinera, 2008).

Caterpillars are famously cannibalistic-often only one survives per corn ear because larger larvae eat smaller ones.

In warm summer conditions the insect can complete egg→adult in roughly ~30 days (egg ~2-4 d; larva ~14-21 d; pupa ~10-14 d), but timing stretches in cool weather (Capinera, 2008).

Adults are strong fliers and can recolonize northern regions each year from warmer areas; multi-generation seasonal movement is a key part of its pest status in North America (extension syntheses).

Unique Adaptations

  • Extreme polyphagy: H. zea uses many host plants (often cited 100+), enabled by flexible feeding behavior and detoxification enzyme systems typical of noctuid generalists (Capinera, 2008).
  • Rapid development in heat: short generation time in warm weather (often ~1 month egg→adult) allows quick population buildup during crop flowering/fruiting windows.
  • Color polymorphism in larvae: caterpillars vary from green to tan/brown/pinkish with striping-useful camouflage across different crops and plant parts.
  • Diapause capability (regional): pupae can suspend development to survive unfavorable seasons, improving persistence where winters limit year-round breeding.
  • Strong flight capacity: adults disperse efficiently, promoting reinfestation of fields and gene flow that can accelerate the spread of insecticide/Bt resistance traits (documented in pest-management literature).
  • Behavioral "protected feeding" habit: larvae often feed within ears, bolls, or folded plant tissues, physically shielding them from contact insecticides and some natural enemies.

Interesting Behaviors

  • Nocturnal activity: adults fly and mate mainly at night; females oviposit during evening/night, placing eggs singly on silks, leaves, buds, or terminals (Capinera, 2008).
  • Targeting reproductive tissues: larvae preferentially feed on ears (corn), bolls (cotton), and fruiting structures (tomato/pepper), which causes disproportionate yield and quality losses.
  • Cannibalism as a spacing mechanism: in confined sites like a corn ear tip, larvae attack and consume competitors, often leaving a single dominant larva.
  • Soil pupation: mature larvae leave the plant and burrow into soil to pupate, typically a few centimeters down (commonly reported ~2-8 cm depending on soil; extension references).
  • Seasonal phenology and generation turnover: multiple generations per year in warm regions; later-season individuals may enter diapause as pupae where winters are cold (Capinera, 2008).
  • Adult nectar feeding: moths visit flowers for nectar, fueling dispersal and egg production.
  • Pheromone-mediated mating: females emit sex pheromones; monitoring traps using synthetic pheromone lures are standard tools for timing scouting and interventions in IPM programs.

Cultural Significance

Helicoverpa zea (corn earworm or cotton bollworm) is a major farm pest in North America. It harms corn, cotton, tomatoes, and other crops, and led to pheromone traps, timed sprays, Bt crops, and resistance research.

Myths & Legends

Earworm and bollworm are old farm names for the Corn Earworm (Helicoverpa zea). They come from larvae boring into corn ears and cotton bolls, used in grower stories before the moth's scientific name.

In many U.S. cotton and sweet-corn areas, "bollworm years" (Corn Earworm, Helicoverpa zea) are remembered as times when night-flying moths ruined ears and bolls, forcing long days of hand-checking fields and emergency spraying.

In farmer education, the Corn Earworm (Helicoverpa zea) is the classic "hidden feeder"—it shows damage can be inside ears or fruit while leaves look fine, so farmers must inspect silks, ears, and bolls.

For decades Helicoverpa zea was seen as the New World match to the Old World cotton bollworm (Helicoverpa armigera). Ports and produce trade often asked "which bollworm?" as tests and biosecurity improved.

Conservation Status

NE Not Evaluated

Has not yet been evaluated against the criteria.

Population Unknown

Life Cycle

Birth 1000 larvas
Lifespan 45 years

Lifespan

In the Wild
30–270 years
In Captivity
33–55 years

Reproduction

Mating System Promiscuity
Social Structure Solitary
Breeding Pattern Transient
Fertilization Internal Fertilization
Birth Type Internal_fertilization

Helicoverpa zea is a moth active at night, solitary, with no pair bonds or parental care. Females use pheromones; males fly upwind and receive a spermatophore (internal fertilization). Adults live ~1–2 weeks; females lay hundreds to >1,000 single eggs and often remate.

Behavior & Ecology

Social Solitary Group: 1
Activity Nocturnal, Crepuscular
Diet Herbivore Maize/corn ear tissues-especially fresh silks followed by developing kernels (earworm feeding in ears)
Seasonal Migratory, Hibernates 1,056 mi

Temperament

Larvae: strongly aggressive and cannibalistic toward conspecifics, especially under crowding or limited food; this drives a predominantly solitary feeding outcome in confined plant structures (e.g., ears/bolls/buds) reported in pest biology syntheses (Capinera, 2017).
Adults: non-aggressive and non-territorial; primarily evasive/avoidant, with brief reproductive interactions.
Both stages: behavior is opportunistic and resource-driven rather than cooperative; apparent 'grouping' is usually incidental co-location at food/oviposition sites rather than affiliation.

Communication

Long-range sex pheromones: females 'call' and release a species-specific pheromone blend that attracts males downwind; mate-finding is primarily chemical Hardwick, 1965; widely documented for H. zea pheromone-mediated attraction in pheromone-trap literature
Short-range chemical/tactile cues during courtship: antennal contact and contact chemoreception help finalize mate recognition and copulation in close proximity Hardwick, 1965
Plant-odor/host volatile cues: adults use olfaction to locate nectar resources and suitable host plants for oviposition; this can concentrate multiple individuals in the same habitat patch without true social structure Capinera, 2017
Indirect chemical cues among larvae: presence of conspecifics is detected via contact/chemosensory cues, often triggering avoidance or aggression/cannibalism rather than aggregation Reported broadly for Helicoverpa larval ecology in pest syntheses such as Capinera, 2017

Habitat

Agricultural/Farmland Plantation Grassland Prairie Shrubland Woodland Deciduous Forest Urban Suburban Coastal +4
Biomes:
Temperate Grassland Temperate Forest Mediterranean Savanna Tropical Dry Forest Tropical Rainforest Desert Hot +1
Terrain:
Plains Valley Hilly Coastal Riverine
Elevation: Up to 8202 ft 1 in

Ecological Role

Polyphagous herbivore and major agricultural pest of row and vegetable crops; adults are nectar-feeding moths that can contribute minor pollination while larvae strongly impact plant reproductive success by consuming flowers/fruit/seeds.

Trophic link supporting predators and parasitoids (e.g., tachinid flies and braconid/ichneumonid wasps that utilize corn earworm larvae as hosts) Minor nocturnal pollination via adult nectar feeding Ecosystem disservice: substantial crop yield/quality losses by larval feeding on ears/bolls/fruit (key pest status in maize, cotton, tomato, etc.)

Diet Details

Other Foods:
Maize reproductive tissues Cotton Tomato fruit Sorghum panicle Larvae Tobacco buds and capsules Pepper fruit Okra pods Floral nectar +3

Human Interaction

Domestication Status

Wild

Helicoverpa zea (corn earworm, cotton bollworm, tomato fruitworm) is a wild, migratory moth native to the Americas and is not domesticated. It is often bred in large numbers in labs for research and pest-control tests (insecticide and Bt resistance, pheromone and host-plant studies), but lab colonies are not true domestication.

Danger Level

Low
  • Not venomous and not known to transmit human disease; direct medical risk is minimal.
  • Occasional minor skin irritation or allergic reactions can occur from handling caterpillars/moth scales (a general lepidopteran handling risk).
  • Indirect risk is significant: because H. zea is a key pest, people may be exposed to insecticides used for its control (occupational/field exposure risk rather than an inherent danger from the insect).
  • Accidental spread via transport of infested produce/plant material can create biosecurity and economic harm (human-mediated dispersal risk).

As a Pet

Not Suitable as Pet

Legality: Corn Earworm (Helicoverpa zea) is not usually a pet. Keeping, moving, or releasing live eggs, larvae, or pupae may be restricted; USDA-APHIS, states, and institutions often require permits and secure housing.

Care Level: Experienced

Purchase Cost: Up to $20
Lifetime Cost: $20 - $150

Economic Value

Uses:
Major agricultural pest (direct yield/quality losses) Driver of insecticide and transgenic (Bt) management costs Target of integrated pest management (IPM) programs Research organism for resistance evolution, pheromone communication, and host-plant interactions HUBS: Across Noctuidae/Helicoverpa, human interactions range from severe crop damage (corn, cotton, tomato, legumes and many others), to intensive monitoring (pheromone traps), to regulated laboratory culture for science; most species are non-pets and interact with people primarily through agriculture, biosecurity, and nighttime attraction to lights.
Products:
  • Pheromone lures/traps used to monitor adult flights (management product tied to this species)
  • Biological control inputs used against larvae (e.g., parasitoids and microbial insecticides such as Bacillus thuringiensis formulations and nucleopolyhedroviruses in IPM programs)
  • Insecticide applications and associated scouting/threshold services
  • Bt crop traits and refuge/IRM (insect resistance management) programs whose economic rationale is partly driven by H. zea damage

Relationships

Predators 11

Egg parasitoid wasp Trichogramma pretiosum
Egg parasitoid wasp Trichogramma brassicae
Parasitoid wasp Cotesia marginiventris
Larval parasitoid wasp Microplitis croceipes
Larval parasitoid wasp Campoletis sonorensis
Tachinid fly Archytas marmoratus
Green lacewing Chrysoperla carnea
Minute pirate bug Orius insidiosus
Big-eyed bug Geocoris punctipes
Spined soldier bug Podisus maculiventris
Red imported fire ant Solenopsis invicta

Related Species 7

Old World bollworm Helicoverpa armigera Shared Genus
Australian native budworm Helicoverpa punctigera Shared Genus
Oriental tobacco budworm Helicoverpa assulta Shared Genus
South American bollworm Helicoverpa gelotopoeon Shared Genus
Tobacco budworm Chloridea virescens Shared Family
Subflexus straw moth Heliothis subflexa Shared Family
Fall armyworm
Fall armyworm Spodoptera frugiperda Shared Family

Ecological Equivalents 5

Animals that fill a similar ecological role in their ecosystem

Old World bollworm Helicoverpa armigera Closest ecological match is Helicoverpa armigera, a heliothine moth that feeds on many plant parts (buds, flowers, bolls, ears, fruits). It causes similar crop damage, exhibits comparable resistance issues, and is similar in size.
Tobacco budworm Chloridea virescens Attacks buds, flowers, and fruit in cotton, tobacco, and other broadleaf crops. Larvae tunnel into protected spots, reducing insecticide effectiveness and prompting use of Bt and resistance monitoring. Often co-occurs with H. zea and is managed with the same scouting methods and pheromone traps.
Fall armyworm
Fall armyworm Spodoptera frugiperda Both are major noctuid pests of maize and other grasses, with multiple generations and a strong ability to migrate, causing crop damage. Spodoptera frugiperda primarily damages whorls and leaves, whereas Helicoverpa zea attacks silks and developing kernels.
European corn borer
European corn borer Ostrinia nubilalis A major corn moth pest that reduces yield and grain quality. It is managed alongside similar species using Bt traits, pheromone traps, and degree-day timing as part of integrated corn IPM.
Southwestern corn borer Diatraea grandiosella Another larva that attacks maize ear, shank, and stalk tissues. It overlaps in phenology and economic impact with Helicoverpa zea (H. zea) in some regions and is often discussed alongside H. zea in corn pest complexes, even though feeding sites differ (boring vs. ear-tip/silk/kernels).

Types of Corn Earworm

1

Explore 1 recognized types of corn earworm

The corn earworm is an insect species of the moth family that is found in a wide range of crops that, include corn, cotton, and beans. It first appeared in Europe in 1886 and quickly traveled to a number of continents by 1890. These moths primarily inhabit South America, parts of Europe, and North America, except northern Canada and Alaska. Due to the harshness of winter, Corn earworms tend to migrate towards warmer climates as it provides them with an abundant food source, allowing this species to mature from caterpillar to moth.

4 Fun Facts

  • The corn earworm is capable of devouring an entire crop in just a few days.
  • Its larvae can be found in more than 200 different types of plants.
  • The adult moths are active during the day when they fly around searching for food sources.
  • Earworms have also been known to migrate over great distances which reach up to 398 miles!

Types of Corn Earworms Species

Corn earworm Helicoverpa zea

Helicoverpa zea is the most prevalent and widespread corn earworm species in the United States and Canada.

©Marcos Cesar Campis/Shutterstock.com

The corn earworm, also known as Helicoverpa zea, is the only species known by its name. However, there are other closely related species within the same genus, called Helicoverpa, which are sometimes referred to as fruit worms.

There are several subspecies of corn earworms, which are listed below:

  1. Helicoverpa zea: Also known to be the most prevalent and widespread corn earworm species in the United States and Canada.
  2. Helicoverpa armigera: Although it was recently discovered in North and South America, this species is native to Africa, Asia, Europe, and Oceania.
  3. Helicoverpa assulta: This species is found in Asia, from the Indian subcontinent to eastern Asia.
  4. Helicoverpa punctigera: Australia and areas of Southeast Asia are home to this species.

In addition, all four of these species resemble one another in terms of appearance and behavior, and they all feed on a variety of crops, including corn, cotton, tomatoes, and soybeans.

The Scientific Name of the Corn Earworm

The corn earworm is an insect that belongs to the family Noctuidae, which represents a family of moths. Helicoverpa zea is its scientific name.

The Appearance of the Corn Earworm

Helicoverpa zea, corn earworm

The corn earworm caterpillars can be various shades including green, pinkish-brown, and black.

©iStock.com/Bhupinder Bagga

The larvae of the corn earworm are tiny, slender caterpillars displaying a variety of colors that include green, pinkish-brown, and sometimes even black. It has three pairs of legs near its head and five pairs of prolegs near its tail. In addition, the tail end of their body consists of a couple of black spots. The larvae can grow up to 1 1\2 inches long when fully grown.

Upon completing their growth, they will form a cocoon and transform into an adult moth. The adult moth can be identified by its unique creamy yellow to olive-tan color tones followed by black stripes, as well as a white spot on its wings. The adult moth measures roughly 1.5 inches in length, boasting a wingspan of up to 2 inches.

Habitat of the Corn Earworm

The corn earworm has a diverse food host range that includes grassy areas, wooded areas, and agricultural fields. Its cultivated hosts consist of:

  • Sweet corn
  • Field corn
  • Green beans
  • Eggplant
  • Peas
  • Peppers
  • Lettuce
  • Sweet potato
  • Rice
  • Cotton
  • Grapes
  • Strawberries

Diet

The larvae of the corn earworm feed voraciously on various plants, particularly flowers, foliage, and vegetables. However, it is especially fond of corn, thus giving it the name corn earworm, derived from its habit of feeding on sweet corn ears.

Adult moths indulge in pollen and nectar found in flowers. Apart from plant material, these ravenous eaters also feast on insects such as aphids and caterpillars.

Lifecycle of the Corn Earworm

Corn earworm moth (Helicoverpa zea)

The corn earworm moth is usually brown or gray and has a wingspan of about 1.2-1.5 inches.

©Davide Bonora/Shutterstock.com

The duration of their life cycle can vary from 30-50 days, depending on temperature and other environmental factors. In addition, it has a life cycle that consists of four stages that include: egg, larva, pupa, and adult.

Egg: The female moth lays between 500 and 1000 eggs on the surface of leaves, maize silk, or other plant parts. The eggs are typically cream or yellowish in color and have a diameter of about 0.5 mm.

Larva: When the eggs hatch after 2-10 days, the larva emerges and starts to feed on the host plant, which can either include corn, cotton, and tomato plants. The larva is typically green, yellow, or brown in color, with a distinct head that has two black spots.

Pupa: After about 2 to 3 weeks of feeding, the larva pupates and forms a cocoon in the soil or in plant debris. The pupa is usually brown or reddish-brown and about 1 cm long.

Adult: After about 1 to 2 weeks of pupation, the adult moth emerges from the cocoon. The moth is usually brown or gray and has a wingspan of about 1.2-1.5 inches.

Prevention of Infestation

Below are some guidelines on how to eradicate an infestation of corn earworm and how to prevent this species from reoccurring.

  • Remove any damaged or infested fruit or vegetables from the plant and dispose of them properly.
  • Inspect the plant regularly for eggs and caterpillars. Corn earworms are usually found on the leaves, stems, or fruit of the plant. You can remove them by hand or use a soft brush to gently brush them off the plant.
  • Apply insecticides; there are several insecticides available that can help control corn earworms, including pyrethroids, carbamates, and organophosphates. Follow the instructions carefully when using any insecticide, and wear protective clothing as recommended.
  • Incorporate natural enemies of corn earworms. Their natural enemies include parasitic wasps, ground beetles, and birds. You can draw these predators to your garden by planting nectar-producing flowers or offering bird nesting sites.
  • You can use physical barriers like netting, or row covers to stop adult moths from depositing their eggs on the plants.
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Sources

  1. Safer Brand / Accessed March 30, 2023
  2. University of Illinois / Accessed March 30, 2023
  3. University of Maryland / Accessed March 30, 2023
  4. Wikipedia / Accessed April 6, 2023
Kayeleen Parsons

About the Author

Kayeleen Parsons

Kayeleen Parsons is a writer at A-Z Animals that thoroughly enjoys writing about animals of all types. She has a love for many animals, but her Cocker Spaniel dog holds a special place in her heart. In addition to being a writer, she's also an English teacher, sharing her knowledge to help her students become excellent in the language and literature. When she's not busy writing, Kayeleen enjoys reading and spending quality time with her family in her homeland of Cape Town.

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Corn Earworm FAQs (Frequently Asked Questions)

The larvae of the corn earworm are tiny, slender caterpillars displaying a variety of colors that include green, pinkish-brown, and sometimes even black. It has three pairs of legs near its head and five pairs of prolegs near its tail. In addition, the tail end of their body consists of a couple of black spots. The larvae can grow up to 1 1\2 inches long when fully grown.

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