Corn Earworm

Helicoverpa zea — the corn earworm (also called the cotton bollworm and tomato fruitworm in different crops) — is one of the most economically important AGRICULTURAL PESTS in North America. The species is widespread across all of North America from southern Canada south through the eastern and central US to South America, with seasonal range expansion north each spring (the species cannot overwinter in cold northern regions and is re-established each spring by southward populations and long-distance migration from year-round overwintering sites in the southern US and Mexico). Larvae are 3-4 cm long, color-polymorphic (variable across individuals — green, brown, pink, or black variants), with longitudinal stripes along the body and a distinctive small head capsule with strong mandibles. Adult moths are medium-sized (3-4 cm wingspan), tan-yellow gray with a dark spot on each forewing — the typical NOCTUID 'OWLET' MOTH appearance. The species is one of the most economically important LEPIDOPTERAN PESTS in NA agriculture and is a major pest of MULTIPLE CROPS: CORN (the most cited host — larvae feed inside developing corn ears, tunneling through the kernels and frass-filling the ear cavity, ruining the grain for both fresh-market corn and processing); COTTON (where the species is called 'COTTON BOLLWORM' — larvae feed inside developing cotton bolls, destroying the cotton fibers and seeds inside); TOMATOES (where it is called 'TOMATO FRUITWORM' — larvae feed inside developing tomato fruits, similar to apple maggot fly but on a different host); SOYBEANS (a major pest of southeastern US soybean production); SORGHUM, COWPEA, and many other crops. The species' EXTREME POLYPHAGY and ability to attack multiple major commodity crops makes it the single most economically important Lepidopteran pest in North American agriculture — and combined with the closely-related Old World cotton bollworm (Helicoverpa armigera), one of the most economically important crop pests in the entire world. Annual NA agricultural losses to corn earworm are estimated at BILLIONS OF DOLLARS, even with intensive insecticide control. The species is the FOUNDATIONAL TARGET SPECIES in the development of GENETICALLY-MODIFIED Bt CROPS. Bt CORN (corn varieties engineered to express the Bacillus thuringiensis bacterial endotoxin, which is highly toxic to lepidopteran larvae) was developed specifically to provide built-in resistance to corn earworm and the closely-related European corn borer (Ostrinia nubilalis). Bt CORN was first commercialized in 1996 and has been one of the most-adopted GMO crops in NA agriculture — currently planted on the majority of US corn acreage. Bt cotton was similarly developed to control corn earworm (cotton bollworm) and is widely used in cotton production. The species is the most-studied case in modern Bt RESISTANCE EVOLUTION research — corn earworm populations have evolved varying levels of resistance to Bt corn over the past 30 years, prompting the development of 'pyramided' Bt traits (multiple Bt toxins in the same plant) and refuge management strategies. The species is harmless to humans (no venom, no bite) but is the single greatest economic threat to North American crop agriculture.