A larva is a distinct juvenile form many animals undergo before metamorphosis into adults. Animals with indirect development such as insects, amphibians, or cnidarians typically have a larval phase of their life cycle...
of the moth
A moth is an insect closely related to the butterfly, both being of the order Lepidoptera. Moths form the majority of this order; there are thought to be 150,000 to 250,000 different species of moth , with thousands of species yet to be described...
(formerly in the genus Heliothis
) is a major agricultural pest. It can feed on many different plants (i.e. it is polyphagous) during the larval stage. Accordingly, the species has been given many different common name
A common name of a taxon or organism is a name in general use within a community; it is often contrasted with the scientific name for the same organism...
s. When the larva consumes cotton
Cotton is a soft, fluffy staple fiber that grows in a boll, or protective capsule, around the seeds of cotton plants of the genus Gossypium. The fiber is almost pure cellulose. The botanical purpose of cotton fiber is to aid in seed dispersal....
, it is known as the cotton bollworm
. When it consumes corn
Maize known in many English-speaking countries as corn or mielie/mealie, is a grain domesticated by indigenous peoples in Mesoamerica in prehistoric times. The leafy stalk produces ears which contain seeds called kernels. Though technically a grain, maize kernels are used in cooking as a vegetable...
, it is known as the corn earworm
. When it consumes tomato
The word "tomato" may refer to the plant or the edible, typically red, fruit which it bears. Originating in South America, the tomato was spread around the world following the Spanish colonization of the Americas, and its many varieties are now widely grown, often in greenhouses in cooler...
es, it is known as the tomato fruitworm
. It has also been known to consume many other crops
Agriculture is the cultivation of animals, plants, fungi and other life forms for food, fiber, and other products used to sustain life. Agriculture was the key implement in the rise of sedentary human civilization, whereby farming of domesticated species created food surpluses that nurtured the...
. The adult moth is a pollinator
A pollinator is the biotic agent that moves pollen from the male anthers of a flower to the female stigma of a flower to accomplish fertilization or syngamy of the female gamete in the ovule of the flower by the male gamete from the pollen grain...
and it is pictured on the right engaging in this process.
The larva (caterpillar) is very aggressive and will bite. It has been known to attack and consume other larvae of the same species.
The impact of this pest has been and continues to be significant, especially because of the wide range of crops attacked, and the natural abundance of the species in the wild.
The cotton bollworm, corn earworm or Old World bollworm, Helicoverpa armigera, is a moth, the larvae of which feed on a wide range of plants, including many important cultivated crops. It is a major pest in cotton and one of the most polyphagous and cosmopolitan pest species...
, a close relative of H. zea
from which the latter evolved, is a major pest in Asia, Africa and Australia.
The insidious flower bug
Orius insidiosus, common name the insidious flower bug, is a species of minute pirate bug, a predatory insect in the order Hemiptera . They are considered beneficial, as they feed on small pest arthropods and their eggs...
), a pirate bug, feeds on the eggs of H. zea
, thus acting as a biological control agent. The braconid wasp Microplitis croceipes
Microplitis croceipes is a braconid wasp native to Georgia. It is an important parasitoid of the caterpillars of Helicoverpa zea and of Heliothis virescens....
, which deposits its eggs inside a living caterpillar, is also an important parasitoid
A parasitoid is an organism that spends a significant portion of its life history attached to or within a single host organism in a relationship that is in essence parasitic; unlike a true parasite, however, it ultimately sterilises or kills, and sometimes consumes, the host...
of both H. zea
and the related species Heliothis virescens
The Tobacco Budworm is a moth of the Noctuidae family. It is found in Virginia, Georgia, Florida, Texas, Mexico, Guatemala, Panama, Brazil and the Antilles. The wingspan is 28-35 mm....
larvae are green, brown, or pinkish with darker longitudinal stripes; they grow to about 3.7 cm (1.5 inches) in length. Adults are most active during the evening and at night. An adult has a body length of approximately 1.9 cm (0.75 inches) and a wingspan of 2.5 to 3.8 cm (1 to 1.5 inches. Its body is yellowish tan with distinctive double lines that are reddish brown, olive green or grey (Coxwell 1984, p. 141). The forewing has several dark marking and a central brown dot. The hindwings are pale in colour and surrounded by a dark brown border. It has a tan coloured head with bright green eyes. The male and female moths are very similar morphologically, which make it difficult to differentiate the two.
The corn earworm is considered to be a major agricultural pest, with a large host range encompassing not only corn, but also numerous other crop plants. Pesticides are one method by which corn earworm populations are controlled; however, since they have been widely used, the insects are resistant to many pesticides. The use of biological controls such as the bacterium Bacillus thuringiensis
and various forms of nematodes is also common, although not without its own problems. Corn earworms are only variably vulnerable to the bacterium, and nematodes are only effective once the larvae have pupated and dropped to the ground.
The corn earworm is found in temperate and tropical regions of the world. It is mainly found in North America, but is not found in northern Canada and Alaska, as it cannot overwinter in these areas. Corn earworm regularly migrates into northern regions from southern regions depending on winter conditions.
Eggs are individually deposited on leaf hairs and corn silks and hatch in about 3 to 4 days. Following hatching, larvae normally feed on the reproductive structures of the plant and usually develop through four to six instars. Older larvae become aggressive and cannibalistic, resulting in one or two larvae per feeding site (Boyd 2008, p. 143). Mature larvae migrate to the soil, where they pupate for 12 to 16 days. Adult moths collect nectar or other plant exudates from a large number of plants, and live for 12 to 16 days. Females lay up to 2500 eggs in their lifetimes.
- Capinera, J.P. http://edis.ifas.ufl.edu/IN302. Corn Earworm, Helicoverpa (=Heliothis) zea (Boddie) (Lepidoptera: Noctuidae), 2008.
- Cooke, K.A., Weinzier, R. http://www.ipm.uiuc.edu/fieldcrops/insects/corn_earworm/index.htmlIPM: Field Crops: Corn Earworm (Heliothis Zea), 2004.
- Coxwell, V.C. (1984) Eastern Moths. Peterson Field Guides. 141pp.
- Hagerman, P. http://www.omafra.gov.on.ca/english/crops/facts/95-065.htm, Corn Earworm Factsheet, 2008.
- Zimmerman, E.C. http://www.extento.hawaii.edu/kbase/Crop/Type/helicove.htm#BIOLOGY, Heliothis zea (Boddie), 1958.
- Boyd, B.M. (2008) Predaceous Behavior by Helicoverpa zea (Boddie) (Lepidoptera: Noctuidae: Heliothinae). Journal of Insect Behavior 21:143-46.
- Hill, D.S.http://www.extento.hawaii.edu/kbase/Crop/Type/helicove.htm#BIOLOGY, Heliothis zea (Boddie), 1983.
- corn earworm on the UF
The University of Florida is an American public land-grant, sea-grant, and space-grant research university located on a campus in Gainesville, Florida. The university traces its historical origins to 1853, and has operated continuously on its present Gainesville campus since September 1906...
The University of Florida’s Institute of Food and Agricultural Sciences is a federal-state-county partnership dedicated to developing knowledge in agriculture, human and natural resources, and the life sciences, and enhancing and sustaining the quality of human life by making that information...
Featured Creatures Web site
- corn earworm moth Find large format diagnostic photos and information.
- J. L. Capinera, Corn Earworm, Helicoverpa (=Heliothis) zea (Boddie) (Lepidoptera: Noctuidae),
- A new synonym of Helicoverpa zea (Boddie) and differentiation of adult males of H. zea and H. armigera (Hübner) (Lepidoptera: Noctuidae: Heliothinae)