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* ''Heliothis stombleri '' <small>Okumura & Bauer, 1969</small>
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'''''Helicoverpa zea''', ''commonly known as the '''corn earworm''', is a species (formerly in the genus ''Heliothis'') in the family [[Noctuidae]].<ref name="
The species is widely distributed across the Americas with the exception of northern Canada and Alaska. It has become resistant to many pesticides, but can be controlled with [[integrated pest management]] techniques including deep ploughing, [[trap crop]]s, chemical control using mineral oil, and [[Biological pest control|biological controls]].
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== Distribution ==
The corn earworm is found in [[Temperate climate|temperate]] and [[tropical]] regions of [[North America]], with the exception of northern [[Canada]] and [[Alaska]] as it cannot [[Overwintering|overwinter]] in these areas.<ref name="extento.hawaii.edu">{{cite web | first1 = Ronald F.L. | last1 = Mau | first2 = Jayma L. Martin | last2 = Kessing | name-list-format = vanc | publisher = Department of Entomology, University of Hawii | title = Helicoverpa zea (Boddie) | url = http://www.extento.hawaii.edu/kbase/Crop/Type/helicove.htm#BIOLOGY | work = Crop Knowledge Master | }}</ref><ref name="edis.ifas.ufl.edu" /> ''Helicoverpa zea'' found in the eastern [[United States]] also does not overwinter successfully.<ref name="edis.ifas.ufl.edu" /> They live in [[Kansas]], [[Ohio]], [[Virginia]], and southern [[New Jersey]], but survival rate is mainly affected by the severity of the winter.<ref name="edis.ifas.ufl.edu" /> Corn earworm moths regularly migrate from southern regions to northern regions depending on winter conditions.<ref name="edis.ifas.ufl.edu" /> They are also found in [[Hawaii]], the [[Caribbean islands]], and most of [[South America]], including [[Peru]], [[Argentina]], and [[Brazil]].<ref>{{cite journal | vauthors = Blanchard
Cotton earworms have also been reported from China in 2002.<ref name="LuLiang2002">{{cite journal | last1 = Lu
The taxonomy of ''[[Helicoverpa]]'' was poorly understood for a long time. Many older works referring to "''Heliothis obsoleta''", a synonym of ''H. armigera'', are actually about ''H. zea''.<ref name="Hardwick1965">{{cite journal |last1=Hardwick |first1=David F. | name-list-format = vanc |year=1965 |title=The corn earworm complex |journal=Memoirs of the Entomological Society of Canada |publisher= |volume=97 |issue=S40 |pages=5-247 |doi=10.4039/entm9740fv |url=https://www.cambridge.org/core/journals/memoirs-of-the-entomological-society-of-canada/article/corn-earworm-complex/89C7B569C797D0A6B813A8B9B6B45B57 |
== Lifecycle and description ==
=== Eggs ===
[[Egg (biology)|Egg]]s are individually deposited on [[leaf]] hairs and corn silks (not in reference given).<ref name=":10" /> The eggs are initially pale green in color, but over time they turn yellowish and then grey.<ref name=":10" /> Eggs are 0.5 mm in height and average about 0.55 mm in [[diameter]].<ref name=":10">{{cite journal | vauthors = Neunzig HH
[[File:Corn earworm, eggs 2014-06-06-10.46.51 ZS PMax (15938018542).jpg|thumbnail|left|190px|Eggs]]
[[File:Helicoverpa zea larva.jpg|thumb|left|205px|Corn earworm larva<ref>{{cite web | title = Helicoverpa zea larva | url = http://www.learner.org/jnorth/images/graphics/monarch/helicoverpa_zea_larva_800.jpg | archive-url = https://web.archive.org/web/20180410071945/http://www.learner.org/jnorth/images/graphics/monarch/helicoverpa_zea_larva_800.jpg | archive-date = 10 April 2018 | work = Annenberg Learner }}</ref>|190x190px]]
=== Larvae ===
Following hatching, larvae feed on the reproductive structures of the plant and usually develop through four to six [[instars]].<ref name="extento.hawaii.edu" /> Initially, the young larva feed together, and this stage is their most destructive stage.<ref name="animals.pawnation.com">{{cite web | title = Life Cycle of Corn Earworms | url = http://animals.pawnation.com/life-cycle-corn-earworms-4256.html | archive-url = https://web.archive.org/web/20131203012122/http://animals.pawnation.com/life-cycle-corn-earworms-4256.html | archive-date = 3 December 2013 | work = PawNation }}</ref> Through [[Developmental biology|maturation]], older larvae become [[aggressive]] and [[cannibalistic]], leaving one or two larvae per feeding site (See [[Helicoverpa zea#Interfamilial Predation|Interfamilial Predation]]).<ref name=":0">{{cite journal | vauthors = BoydBM,
=== Pupae ===
Larvae pupate 5 to 10 cm below the [[soil]] surface.<ref name="extento.hawaii.edu" /> Pupae are brown in color; they measure 5.5 mm wide and 17 to 22 mm long.<ref name="extento.hawaii.edu" /> The biggest environmental factor that affects the pupal developmental rate is [[temperature]], primarily soil temperature.<ref name=":4" /> This is because proper insulation facilitates development, and soil temperatures below 0 degrees Celsius correlate to higher pupal mortality.<ref name=":4" /> Another factor that influences pupal development is soil moisture. Pupal mortality is high in wet soil, where the moisture level is between 18 and 25 percent. [[Dehydration]] can also lead to high death rates among pupae, if soil moisture is as low as 1 to 2 percent.<ref>
=== Adults ===
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=== Damage ===
The corn earworm is a major agricultural pest, with a large [[host (biology)|host]] range encompassing corn and many other crop plants.<ref name="omafra.gov.on.ca">{{cite web | title = Corn Earworm | url = http://www.omafra.gov.on.ca/english/crops/facts/95-065.htm | work = Ministry of Agriculture, Food and Rural Affairs | location = Provence of Ontario }}</ref> ''H. zea'' is the second-most important economic pest species in North America, next to the [[codling moth]].<ref name=":8" />{{Dubious | reason=Outdated | date=June 2015}} The estimated annual cost of the damage is more than US$100 million, though expenditure on [[insecticide]] application has reached up to $250 million.<ref name=":14" /> The moth's high [[fecundity]], ability to lay between 500 and 3,000 eggs, [[polyphagous]] larval feeding habits, high mobility during migration, and a [[facultative]] pupal diapause have led to the success of this pest.<ref name=":14">Capinera, John. Handbook of vegetable pests. Access Online via Elsevier, 2001.</ref><ref name="Fitt, G.P. 1989">Fitt, G.P. (1989) The ecology of Heliothis species in relation to agro-ecosystems. Annual Review of Entomology 34, 17-52.</ref>
=== Control ===
Two kinds of control measures have been advocated since the 19th century.<ref name=":8" /> One aims at total pest population reduction, while the other is aimed at protection of the particular crop.<ref name=":8" /> {{As of|2013}}, [[integrated pest management]] (IPM), an array of techniques and approaches to control pests, was recommended.<ref name=":8" /> Practices such as deep [[ploughing]], mechanical destruction, and trap crops are also used to kill different [[instars]].<ref name=":8" /> Chemical control is widely successful, and includes the use of applying [[mineral oil]] inside the tip of each corn ear, which suffocates the young larvae.<ref name=":8">Hardwick, D.F. (1965) The corn earworm complex. Memoirs of the Entomological Society of Canada 40, 1-247.</ref><ref>{{Cite web |url=http://cru.cahe.wsu.edu/CEPublications/eb1455e/eb1455e.pdf |title=Archived copy |access-date=2013-11-15 |archive-url=https://web.archive.org/web/20120917022044/http://cru.cahe.wsu.edu/CEPublications/eb1455e/eb1455e.pdf |archive-date=2012-09-17 |url-status=dead }}</ref> [[Pesticides]] are one method by which corn earworm populations are controlled; however, since they have been widely used, the insects have become resistant to many pesticides.<ref name="edis.ifas.ufl.edu" /> The use of biological controls, such as the [[bacterium]] ''[[Bacillus thuringiensis]]'' and various forms of [[nematodes]], is also common, although not without their own problems.<ref name="
== Survival ==
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===Migration===
[[File:Corn earworm moth.jpg|thumb|right|253x253px|''Helicoverpa zea ''adult]]
''Helicoverpa zea'' is a [[seasonal]], [[nocturnal]] migrant, and adults disperse, weather permitting, when there are poor reproductive conditions.<ref name=":19" /> In short-range [[Biological dispersal|dispersal]], the moths move within the crop and low over the [[foliage]].<ref name=":19" /> This type of dispersal is mostly independent of wind currents. Long-range dispersal involves adults flying up to 10 meters above the ground and moving [[downwind]] from crop to crop.<ref name=":19" /> Migratory flights occur up to 1–2 km above the ground and can last for hours.<ref>
===Diapause===
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=== Corn ===
[[File:Helicoverpa zea caterpillar.jpg|thumb|175x175px|''Helicoverpa zea'' larva feeding on corn<ref>{{cite journal | title = Image Number K2627-14 | url = http://www.ars.usda.gov/is/graphics/photos/aug11/k2627-14.htm | work = Agricultural Research Service (ARS) | publisher = U.S. Department of Agriculture }}</ref>]]
''Helicoverpa zea'' earns its nickname the corn earworm for its widely known destruction of cornfields.<ref name=":21" /> The corn earworm feeds on every part of corn, including the [[Corn kernel|kernel]]s.<ref name=":21" /> Severe feeding at the tip of kernels allows entry for diseases and [[Mold (fungus)|mold]] growth.<ref name=":21" /> Larvae begin feeding on the kernels once they have reached third [[instar]].<ref name=":21" /> Larvae penetrate 9 to 15 cm into the ear, with deeper penetration occurring as the kernels harden.<ref name=":21" /> Larvae do not eat the hard kernels, but take bites out of many kernels, lowering the quality of the corn for processing.<ref name=":21">Archer, T. L., and E. D. Bynum. "Corn earworm (Lepidoptera: Noctuidae) biology on food corn on the high plains." Environmental entomology 23.2 (1994): 343-348.</ref>
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=== Pheromone production ===
A [[hormone]] produced in the [[brain]] of the female moths controls sex pheromones. The hormone is released into the [[hemolymph]] to stimulate pheromone production.<ref>Raina AK, Klun JA. Brain factor control of sex pheromone production in the female corn earworm moth. Science. 1984;225(4661):531-3.</ref> [[Pheromone Biosynthesis Activating Neuropeptide|Pheromone biosynthesis-activating neuropeptide]] (PBAN) is a [[peptide]] that regulates pheromone production in moths. It acts on the pheromone gland cells using [[calcium]] and [[cyclic AMP]].<ref>Choi, Man-Yeon, et al. "Identification of a G protein-coupled receptor for pheromone biosynthesis activating neuropeptide from pheromone glands of the moth Helicoverpa zea." Proceedings of the National Academy of Sciences 100.17 (2003): 9721-9726.</ref> Although the photoperiod regulates the release of PBAN to some extent, the chemical signals from the host plant supersede the effect from the time of day.<ref name=":22" /> Female ''Helicoverpa zea'' in corn fields do not produce pheromones during the night until they encounter corn. Several natural corn silk [[volatiles]] like the plant hormone [[ethylene]] induce ''H. zea'' pheromone production.<ref name=":22" /> The presence of the silk from an ear of corn is enough to cause pheromone production, and physical contact between females and corn is unnecessary.<ref name=":22" /> This [[evolutionary]] mechanism enables the moths to coordinate their reproductive behavior with the availability of food.<ref name=":22">Raina, Ashok K., Timothy G. Kingan, and Autar K. Mattoo. "Chemical signals from host plant and sexual behavior in a moth." Science 255.5044 (1992): 592-594.</ref> Female moths often become depleted of sex pheromone after mating within 2 hours of separation from the male.<ref name=":9">Kingan, Timothy G., Patricia A. Thomas-Laemont, and Ashok K. Raina.『Male accessory gland factors elicit change from ‘virgin’ to ‘mated’ behaviour in the female corn earworm moth Helicoverpa zea.』Journal of Experimental Biology 183.1 (1993): 61-76.</ref> The pheromonostatic peptide (PSP), a [[protein]] 57 [[amino acids]] long found in the male accessory gland, is what causes depletion of the female's sex pheromone.<ref>Kingan, Timothy G., et al. "The loss of female sex pheromone after mating in the corn earworm moth Helicoverpa zea: identification of a male pheromonostatic peptide." Proceedings of the National Academy of Sciences 92.11 (1995): 5082-5086.</ref> This capability in males has been selected for because it increases the reproductive fitness of those that carry it, since other males will not be attracted to a female without a sex pheromone; thus, the female will bear only the first male's offspring.<ref name=":23" /> The transfer of a [[spermatophore]] without accessory gland products does not stop female pheromone production, but does stop the female's calling behavior.<ref name=":23" /> Intense selection acting on males to manipulate female reproductive [[physiology]] promotes rapid evolution of specific molecules, and male-derived pheromone suppressing factors exhibit [[positive selection]].<ref name=":23">Wedell, Nina. "Female receptivity in butterflies and moths." Journal of Experimental Biology 208.18 (2005): 3433-3440.</ref> When females are infected with the virus [[Helicoverpa zea nudivirus 2|''Helicoverpa zea'' nudivirus 2]], they produce 5 to 7 times the amount of sex pheromone than uninfected females.<ref>{{
[[File:HelicoverpazeaAdultVentral.JPG|thumb|200x200px|''Helicoverpa zea ''adult<ref>{{cite web | title = Helicoverpa zea larva | url = http://www.learner.org/jnorth/images/graphics/monarch/helicoverpa_zea_adult_800.jpg | archive-url = https://web.archive.org/web/20180410071945/http://www.learner.org/jnorth/images/graphics/monarch/helicoverpa_zea_adult_800.jpg | archive-date = 10 April 2018 | work = Annenberg Learner }}</ref>]]
=== Mortality ===
[[Sperm]] competition and chemicals introduced to females through mating have a negative effect on females and their lifespan.<ref name=":23" /><ref name=":24" /> In males, production of the spermatophore, sperm, and secondary chemicals reduces their lifespan.<ref name=":24" /> As the number of copulations increase, the rate of mortality also increases in both sexes.<ref name=":24">
=== Flight behavior ===
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</gallery>
== References ==
{{reflist|30em}}
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*Hill, D.S.[http://www.extento.hawaii.edu/kbase/Crop/Type/helicove.htm#BIOLOGY], ''Heliothis zea (Boddie)'', 1983. <!--accessed February 20, 2009-->
== External links ==
{{wikispecies}}
{{commons}}
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