Helicoverpa zea

Larvae distinguished from fall armyworm by absence of inverted 'Y' suture on head capsule. From Heliothis virescens, requires microscopic examination of male genitalia or molecular methods (ITS1 marker, immunoassay). Eggs on soybean: barrel-shaped, creamy-white with light brown ring below apex, larger (~3,500 eggs/g) than related species. Adults: forewing dark spot and yellowish-brown ground color; distinguishable from H. armigera only by genitalia dissection or genetic analysis.

Agricultural landscapes, particularly fields of host crops. Larvae develop on reproductive structures of plants. Adults hide in vegetation during daylight hours. Pupation occurs in soil.

Widely distributed across temperate and tropical regions of North, Central, and South America. Found throughout the United States except northernmost areas where winter mortality prevents overwintering; regular seasonal migration recolonizes these regions. Established in Hawaii and Caribbean islands. Reported from China (2002). Cannot overwinter successfully in northern Canada, Alaska, or the eastern United States north of approximately Kansas, Ohio, Virginia, and southern New Jersey.

Year-round activity in tropical and subtropical regions. In temperate zones, adults migrate northward from southern overwintering areas in spring and summer. Peak activity varies by region and crop: corn silking period, cotton flowering, soybean pod development. Multiple generations per year where conditions permit; generation time shortened at higher temperatures.

Highly polyphagous larvae feed primarily on reproductive structures of plants. Major hosts include corn (silks and kernels), cotton (bolls), tomato (fruits), soybean (pods and seeds), sorghum, and numerous other vegetable and field crops. Larvae also exhibit cannibalism and predation on other insects when larval densities are high or plant quality is low. Adults feed on nectar and plant exudates.

• Zea mays - primary hostFeeds on silks and kernels; major economic impact
• Gossypium hirsutum - primary hostDamages cotton bolls
• Solanum lycopersicum - primary hostFeeds on tomato fruits
• Glycine max - increasingly important hostPod and seed feeding; rising pest status in mid-south U.S.
• Sorghum bicolor - preferred hostHeads grazed for developing seeds
• Helianthus annuus - host
• Phaseolus vulgaris - hostPod and seed feeding
• Nicotiana tabacum - host

Eggs laid singly on leaf hairs, silks, or other plant parts; hatch in 66–72 hours. Larvae pass through 4–6 instars, feeding gregariously when young, becoming solitary and cannibalistic as they mature. Mature larvae drop to soil and pupate 5–10 cm below surface for 12–16 days. Pupae may enter facultative diapause in response to temperature, photoperiod, or drought. Adults emerge, live 5–15 days on average (up to 30+ days in optimal conditions). Females produce 500–2,500 eggs. Generation time temperature-dependent; more generations at lower latitudes and in warmer years.

Adults are nocturnal, hiding in vegetation during day. Seasonal nocturnal migrants; short-range dispersal within crops independent of wind, long-range dispersal up to 400 km downwind at altitudes of 1–2 km. Males engage in thermoregulatory shivering to reach optimal thoracic temperature (~26°C) before takeoff; respond to female pheromone plumes with rapid directed flight. Larvae become increasingly aggressive with age, attacking and consuming other insects including conspecifics.

Major herbivore in agricultural ecosystems. Significant prey for generalist predators and parasitoids; over 100 insect species recorded as natural enemies. Important host for parasitoid wasps including Cardiochiles nigriceps and Microplitis croceipes. Larval cannibalism and intraguild predation may regulate population densities. Fungal pathogen Nomuraea rileyi can cause epizootics at high larval densities.

Second most economically important lepidopteran pest in North America (after codling moth). Annual damage and control costs exceed $100 million, with insecticide expenditures up to $250 million. Resistance to multiple insecticide classes and Bt toxins complicates management. Subject of integrated pest management programs incorporating biological control, cultural practices, and chemical control. Hybridization with invasive H. armigera has introduced novel resistance genes, threatening control efficacy.

• Helicoverpa armigeraPhenotypically nearly identical; distinguished reliably only by male genitalia morphology or molecular markers. Recently established in Americas and hybridizing with H. zea.
• Heliothis virescensOverlapping host range and distribution; eggs and larvae require immunoassay or feeding disruption bioassay for reliable separation. Slightly smaller eggs (~5,000 vs ~3,500 eggs/g).
• Spodoptera frugiperdaLarvae similar in size and coloration; distinguished by presence of inverted 'Y' pattern on head capsule in fall armyworm.

Older literature referring to 'Heliothis obsoleta' often actually concerns H. zea, not H. armigera as the name would suggest. The common name 'American bollworm' for H. armigera is misleading as that species is native to the Old World.

• agricultural pest
• polyphagous
• migratory
• insecticide resistant
• Noctuidae
• Heliothinae

• BugGuide
• Wikipedia
• GBIF taxonomy match
• iNaturalist taxon
• NCBI Taxonomy
• Catalogue of Life
• Alfalfa Insects - AgriLife Extension Entomology
• Learnings From Latin America: Potential Risk of Helicoverpa armigera to U.S. Soybean Production
• Bollworms rising! | Beetles In The Bush
• Life at 8X—Guide to lepidopteran eggs on soybean | Beetles In The Bush
• How Climate Change May Accelerate Corn Earworm's Resistance to Bt Crops
• Introgression: How the Corn Earworm Borrowed Insecticide Resistance From an Invasive Cousin
• Evaluating cross-resistance and synergy between Vip3Aa and Cry proteins from Bt in six strains of Helicoverpa zea derived via F(2) screens.