Helicoverpa zea (American cotton bollworm)
- Taxonomic Tree
- Notes on Taxonomy and Nomenclature
- Distribution Table
- Risk of Introduction
- Hosts/Species Affected
- Host Plants and Other Plants Affected
- Growth Stages
- List of Symptoms/Signs
- Biology and Ecology
- Natural enemies
- Notes on Natural Enemies
- Detection and Inspection
- Similarities to Other Species/Conditions
- Prevention and Control
- Links to Websites
- Distribution Maps
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PicturesTop of page
IdentityTop of page
Preferred Scientific Name
- Helicoverpa zea (Boddie, 1850)
Preferred Common Name
- American cotton bollworm
Other Scientific Names
- Bombyx obsoleta Fabricius
- Chloridea obsoleta Fabricius
- Heliothis armigera auct.nec Huebner Hübner
- Heliothis ochracea Cockerell
- Heliothis umbrosa Grote
- Heliothis zea Boddie
- Phalaena zea (Boddie)
International Common Names
- English: bollworm, American; corn earworm; cotton bollworm; tomato fruitworm
- Spanish: bellotero; elotero; gusano bellotero del algodon; gusano de la bellota del algodón; gusano de la mazorca; gusano de la mazorca del maiz; gusano de las cápsulas; gusano del elote del maíz; gusano del fruto del tomate; gusano elotero; noctua del tomate; oruga de la mazorca
- French: chenille des epis du mais; noctuelle de la tomate; noctuelle des tomates; ver de la capsule; ver de l'épi du maïs
Local Common Names
- Argentina: isoca del maiz
- Brazil: lagarta da espiga do milho; lagarta das espicas
- Denmark: amerikansk bomuldsugle
- Germany: Amerikanischer Baumwollkapselwurm; Wurm, Amerikanischer Baumwollkapsel-
- Italy: elotide del cotone; elotide del granturco; elotide del pomodoro; elotide del tomato; nottua del granturco; nottua gialla del granturco
- Netherlands: Mimosa-rups
- Turkey: yesil kurt
- HELIZE (Helicoverpa zea)
Taxonomic TreeTop of page
- Domain: Eukaryota
- Kingdom: Metazoa
- Phylum: Arthropoda
- Subphylum: Uniramia
- Class: Insecta
- Order: Lepidoptera
- Family: Noctuidae
- Genus: Helicoverpa
- Species: Helicoverpa zea
Notes on Taxonomy and NomenclatureTop of page The taxonomic situation regarding H. zea is complicated and presents several problems. Hardwick (1965) reviewed the New World corn earworm species complex and the Old World African bollworms, most of which had previously been referred to as a single species (Heliothis armigera or H. obsoleta), and pointed out that there was a complex of species and subspecies involved. Specifically, he proposed that the New World H. zea (first used in 1955) was distinct from the Old World H. armigera on the basis of male and female genitalia; he described the new genus Helicoverpa to include these important pest species. Some 80 or more species were formerly placed in Heliothis (sensu lato) and Hardwick referred 17 species (including 11 new species) to Helicoverpa on the basis of differences in both male and female genitalia. Within this new genus the zea group contains eight species, and the armigera group two species with three subspecies (Hardwick, 1970).
Because the old name of Heliothis for the pest species (four major pest species and three minor) is so well established in the literature, and since dissection of genitalia is required for identification, there has been resistance to the name change (for example, Heath and Emmet, 1983), but Hardwick's work is generally accepted and so the name change must also be accepted (Matthews, 1991).
DescriptionTop of page Egg
Eggs are subspherical, radially ribbed, 0.52 mm high and 0.59 mm in diameter, stuck singly to the plant substrate, green when laid, turning red and finally grey before hatching. Egg maturity takes 2-3 days at 20-30°C. Eggs are usually located on the silk of maize, or on fruiting structures.
On hatching, the tiny grey caterpillars have a black head; they grow through six instars usually, but five and seven instars are not uncommon, and the final body size is approximately 40 mm long. In the third instar, two colour phases can develop: brown (the predominant phase) and green (less frequent). Longitudinal lines of white, cream or yellow are present, and the spiracular band is the most distinct. As the larvae develop, the pattern becomes better defined, but in the final instar (sixth) the coloration changes abruptly into a bright pattern, often pinkish, and with extra striations. Larvae have 5 pairs of prolegs.
Pupae are light to dark brown depending on maturity and approximately 20 mm long, with two distinct terminal cremaster spines. Pupae are located 5-15 cm below the soil surface in earthen cells.
A stout-bodied (20-25 mm long) brown moth of wing-span 38-43 mm; forewing pale brown (female) to greenish (male) with darker transverse markings, underwings pale with a broad dark marginal band.
DistributionTop of page H. zea is confined to the New World. It occurs throughout the Americas from Canada to Argentina (IIE, 1993).
Distribution TableTop of page
The distribution in this summary table is based on all the information available. When several references are cited, they may give conflicting information on the status. Further details may be available for individual references in the Distribution Table Details section which can be selected by going to Generate Report.
|Continent/Country/Region||Distribution||Last Reported||Origin||First Reported||Invasive||Reference||Notes|
|China||Present||Present based on regional distribution.|
|-Anhui||Present||Lu and Liang, 2002|
|Canada||Restricted distribution||EPPO, 2014|
|-British Columbia||Present||EPPO, 2014|
|-New Brunswick||Present||EPPO, 2014|
|-Nova Scotia||Present||EPPO, 2014|
|-New Hampshire||Present||EPPO, 2014|
|-New Jersey||Present||EPPO, 2014|
|-New Mexico||Present||EPPO, 2014|
|-New York||Present||EPPO, 2014|
|-North Carolina||Present||EPPO, 2014|
|-North Dakota||Present||EPPO, 2014|
|-Rhode Island||Present||EPPO, 2014|
|-South Carolina||Present||EPPO, 2014|
|-South Dakota||Present||EPPO, 2014|
|-West Virginia||Present||EPPO, 2014|
Central America and Caribbean
|Antigua and Barbuda||Present||EPPO, 2014|
|Costa Rica||Present||EPPO, 2014|
|Dominican Republic||Present||EPPO, 2014|
|El Salvador||Present||EPPO, 2014|
|Puerto Rico||Present||EPPO, 2014|
|Saint Kitts and Nevis||Restricted distribution||EPPO, 2014|
|Saint Lucia||Present||EPPO, 2014|
|Saint Vincent and the Grenadines||Present||EPPO, 2014|
|Trinidad and Tobago||Widespread||EPPO, 2014|
|United States Virgin Islands||Present||EPPO, 2014|
|-Goias||Present||Marchiori et al., 2002|
|-Minas Gerais||Present||EPPO, 2014|
|-Rio de Janeiro||Present||EPPO, 2014|
|-Rio Grande do Sul||Present||EPPO, 2014|
|-Santa Catarina||Present||EPPO, 2014|
|-Sao Paulo||Present||EPPO, 2014|
|-Easter Island||Present||Olivares et al., 2011|
|Falkland Islands||Present, few occurrences||EPPO, 2014|
|French Guiana||Present||EPPO, 2014|
|Switzerland||Absent, intercepted only||EPPO, 2014|
|UK||Absent, intercepted only||Seymour and, 1978|
Risk of IntroductionTop of page
H. zea was recently added to the EPPO A1 list of quarantine pests, and is also considered as a quarantine pest by APPPC. Originally, H. zea was considered as practically synonymous with H. armigera, an A2 quarantine pest (EPPO/CABI, 1996). The addition to the EPPO list harmonizes it with EU Directive Annex I/A1.
For the related H. armigera, EPPO (EPPO, 1990) makes recommendations on phytosanitary measures which would also be suitable for H. zea. According to these, imported propagation material should derive from an area where H. armigera does not occur or from a place of production where H. armigera has not been detected during the previous 3 months.
Bibliographies are included in the monograph by Hardwick (1965) (2000 titles on H. zea), and the reviews by Fitt (1989) (194 titles), and King and Coleman (1989) (159 references). Most of the basic research on H. zea was done in the early 1900s and published under early synonyms. Many references to H. zea are made in publications relating to the cultivation/protection of specific crops, for example, Chiang (1978), COPR (1983), and Pitre (1985).
Hosts/Species AffectedTop of page H. zea is polyphagous in feeding habits but it shows a definite preference in North America for young maize cobs and tassels, and particularly for the cultivars grown as sweetcorn and popcorn, and also for Sorghum. Most hosts are recorded from the Poaceae, Malvaceae, Fabaceae and Solanaceae; in total more than 100 plant species are recorded as hosts. A feeding preference is shown for flowers and fruits of host plants.
For further information see Barber (1937), Neunzig (1963), Davidson and Peairs (1966) and Matthews (1991).
Host Plants and Other Plants AffectedTop of page
|Abelmoschus esculentus (okra)||Malvaceae||Main|
|Abutilon theophrasti (velvet leaf)||Malvaceae||Other|
|Arachis hypogaea (groundnut)||Fabaceae||Other|
|Brassica oleracea (cabbages, cauliflowers)||Brassicaceae||Other|
|Brassica oleracea var. botrytis (cauliflower)||Brassicaceae||Other|
|Brassica oleracea var. capitata (cabbage)||Brassicaceae||Other|
|Cajanus cajan (pigeon pea)||Fabaceae||Main|
|Capsicum annuum (bell pepper)||Solanaceae||Main|
|Chenopodium quinoa (quinoa)||Chenopodiaceae||Other|
|Cicer arietinum (chickpea)||Fabaceae||Other|
|Cucumis melo (melon)||Cucurbitaceae||Other|
|Cucumis sativus (cucumber)||Cucurbitaceae||Other|
|Fragaria ananassa (strawberry)||Rosaceae||Other|
|Geranium carolinianum (Carolina geranium)||Geraniaceae||Other|
|Gerbera (Barbeton daisy)||Asteraceae||Other|
|Glycine max (soyabean)||Fabaceae||Main|
|Helianthus annuus (sunflower)||Asteraceae||Main|
|Ipomoea purpurea (tall morning glory)||Convolvulaceae||Other|
|Lactuca sativa (lettuce)||Asteraceae||Other|
|Lamium amplexicaule (henbit deadnettle)||Lamiaceae||Other|
|Lespedeza juncea var. sericea (Sericea lespedeza)||Fabaceae||Other|
|Lonicera japonica (Japanese honeysuckle)||Caprifoliaceae||Wild host|
|Medicago lupulina (black medick)||Fabaceae||Other|
|Medicago sativa (lucerne)||Fabaceae||Other|
|Nicotiana tabacum (tobacco)||Solanaceae||Other|
|Panicum miliaceum (millet)||Poaceae||Other|
|Phaseolus vulgaris (common bean)||Fabaceae||Main|
|Securigera varia (crown vetch)||Fabaceae||Other|
|Solanum lycopersicum (tomato)||Solanaceae||Main|
|Solanum melongena (aubergine)||Solanaceae||Main|
|Sorghum bicolor (sorghum)||Poaceae||Main|
|Spinacia oleracea (spinach)||Chenopodiaceae||Other|
|Trifolium incarnatum (Crimson clover)||Fabaceae||Other|
|Vicia sativa (common vetch)||Fabaceae||Other|
|Vicia villosa (hairy vetch)||Fabaceae||Wild host|
|Vigna unguiculata (cowpea)||Fabaceae||Other|
|Zea mays (maize)||Poaceae||Main|
|Zea mays subsp. mays (sweetcorn)||Poaceae||Main|
Growth StagesTop of page Flowering stage, Fruiting stage, Vegetative growing stage
SymptomsTop of page Fruiting structures are consumed or damaged and feeding damage also facilitates entry by diseases and other insect pests. In cotton the square (flower bud), flowers and young bolls are attacked and larvae excavate the interior. Young shoots and leaves can also be damaged, especially in the absence of fruiting structures.
Young maize plants have serial holes in the leaves following whorl feeding on the apical leaf. On larger plants the silks are grazed and eggs can be found stuck to the silks. As the ears develop, the soft milky grains in the top few centimeters of the cobs are eaten; usually only one large larva per cob can be seen. Ear damage is often localized to the tip but can increase the incidence of disease.
Sorghum heads are grazed. Legume pods are holed and the seeds eaten. Bore holes can be seen in tomato fruits, cotton bolls, cabbage and lettuce hearts, and flower heads.
List of Symptoms/SignsTop of page
|Fruit / external feeding|
|Fruit / internal feeding|
|Growing point / external feeding|
|Growing point / internal feeding; boring|
|Inflorescence / external feeding|
|Inflorescence / internal feeding|
|Leaves / external feeding|
|Seeds / external feeding|
|Seeds / internal feeding|
Biology and EcologyTop of page Eggs are laid mostly on the silks of maize plants in small numbers (one to three), stuck to the plant tissues. Choice of oviposition site by the female seems to be governed by a combination of physical and chemical cues. Female fecundity can be dependent upon the quality and quantity of larval food, and also on the quality of adult nutrition. Up to 3000 eggs have been laid by a single female in captivity, but 1000-1500 per female is more usual in the wild. Hatching occurs after 2-4 days and the eggs change colour from green through red to grey. The tiny grey larvae first eat the eggshell and after a short rest they wander actively for a while before starting to feed on the plant. They usually feed on the silks initially and then on the young tender kernels after entering the tip of the husk. By the third instar the larvae become cannibalistic and usually only one larva survives per cob. Feeding damage is typically confined to the tip of the cob. Larval development usually takes 14-25 (mean 16) days, but under cooler conditions 60 days are required. In the final instar (usually sixth) feeding ceases and the fully fed caterpillar leaves the cob and descends to the ground. It then burrows into the soil for some 10-12 cm and forms an earthen cell, where it rests in a prepupal state for a day or two, before finally pupating. Two basic types of pupal diapause are recognized, one in relation to cold and the other in response to arid conditions. In the tropics pupation takes 10-14 (mean 13) days; the male takes 1 day longer than the female. Diapausing pupae are viable as far north as 40-45°N in the USA.
Adults are nocturnal in habit and emerge in the evenings. Maize fields in the USA regularly produce 40,000 to 50,000 adult moths per hectare. Flying adults respond to light radiation at night and are attracted to light traps (Hardwick, 1968), especially the ultraviolet type, in company with many other local noctuids. Sex aggregation pheromones have been identified and synthesized for most of the Heliothis/Helicoverpa pest species, and pheromone traps can be used for population monitoring. Adult longevity is recorded as being about 17 days in captivity; they drink water and feed on nectar from both floral and extra-floral nectaries. The moths fly strongly and are regular seasonal migrants, flying hundreds of kilometres from the USA into Canada. They migrate by flying high with prevailing wind currents.
The life cycle can be completed in 28-30 days at 25°C and in the tropics there may be up to 10-11 generations per year. All stages of the insect are to be found throughout the year if food is available, but development is slowed or stopped by either drought or cold. In the northern USA there are only two generations per year, in Canada only one generation.
For more information, see Hardwick (1965), Beirne (1971), Balachowsky (1972), Allemann (1979), King and Saunders (1984) and Fitt (1989).
Means of Movement/Dispersal
H. zea is a facultative seasonal nocturnal migrant, and adults migrate in response to poor local conditions for reproduction, when weather conditions are suitable. Three types of movement are practiced by Helicoverpa moths: short-range, long-range, and migration. Short-range dispersal is usually within the crop and low over the foliage, and largely independent of wind currents. Long-range flights are higher (up to 10 m), further (1-10 km), and usually downwind, from crop to crop. Migratory flights occur at higher altitudes (up to 1-2 km) and may last for several hours. The moths can be carried downwind hundreds of kilometres; 400 km is not uncommon for such a flight. There is now evidence that many of them originate in Mexico as young adults and migrate northwards into the USA in the early spring. Probably three generations are required to effect the annual displacement from Mexico up to southern Ontario. Transatlantic dispersal is clearly a possibility for this moth, although it has not yet been demonstrated.
Air-freight transportation of agricultural produce from the New World to Europe is an ever increasing commercial enterprise, especially with vegetables and ornamentals. Almost every year, caterpillars of H. zea are intercepted on this produce in the UK (Seymour, 1978).
Natural enemiesTop of page
|Natural enemy||Type||Life stages||Specificity||References||Biological control in||Biological control on|
|Bacillus thuringiensis alesti||Pathogen||Larvae|
|Bacillus thuringiensis israelensis||Pathogen||Larvae|
|Bacillus thuringiensis kurstaki||Pathogen||Larvae|
|Bacillus thuringiensis thuringiensis||Pathogen||Larvae|
|Cytoplasmic polyhedrosis virus (CPV)||Pathogen||Larvae|
|cytoplasmic polyhedrosis viruses||Pathogen||Larvae|
|Helicoverpa armigera nuclear polyhedrosis virus||Pathogen||Adults/Larvae|
|Heliothis nucleopolyhedrosis virus||Pathogen|
|Nomuraea rileyi||Pathogen||Larvae||USA; South Carolina||soyabeans|
|Paratriphleps laeviusculus||Predator||USA||cotton; maize; tomatoes|
|Trichogramma pretiosum||Parasite||Eggs||California; Nicaragua; Nova Scotia; Texas; USA; Texas||cotton|
Notes on Natural EnemiesTop of page Kogan et al. (1989) provides a full list of natural enemy records.
ImpactTop of page In North America it is reported that H. zea is the second most important economic pest species (preceded by codling moth, Cydia pomonella) (Hardwick, 1965). Fitt (1989) quotes the estimated annual cost of damage by H. zea and H. virescens together on all crops in the USA as more than US$ 1000 million, despite the expenditure of US$ 250 million on insecticide application.
Reasons for the success and importance of this agricultural pest include its high fecundity, polyphagous larval feeding habits, high mobility of both larvae locally and adults with their facultative seasonal migration, and a facultative pupal diapause.
Damage is usually serious and costly because of the larval feeding preference for the reproductive structures and growing points rich in nitrogen (for example, maize cobs and tassels, sorghum heads, cotton bolls and buds, etc), and they have a direct influence on yield. Many of the crops attacked are of high value (cotton, maize, tomatoes). If this pest should become established in protected cultivation economic damage could be widespread.
Infestations of maize grown for silage or for grain are not of direct economic importance; losses are typically about 5% and no control measures are taken, but they serve as a focus, or reservoir of infestation. In many areas the first generation is not regarded as a pest (often on Trifolium) and it does not become an economic pest on cultivated crops until the second, third or even fourth generation.
Detection and InspectionTop of page Feeding damage is usually visible and the larvae can be seen on the surface of plants but often they are hidden within plant organs (flowers, fruits, etc). Bore holes may be visible, but otherwise it is necessary to cut open the plant organs to detect the pest. Because of morphological similarity, it is impossible to distinguish the larvae of H. zea from those of Heliothis armigera, already present in the EPPO region. Positive identification is achieved by rearing the larvae and examining the genitalia of the adult.
Similarities to Other Species/ConditionsTop of page The adults are similar in appearance to Heliothis armigera, but differ in several details in their genitalia (Hardwick, 1965); dissection and slide-mounting are required for specific determination, and some aspects are comparative so that a series of closely related species have to be available for comparison.
Prevention and ControlTop of page
Control of H. zea has been advocated in the USA since the middle of the nineteenth century, and measures fall into two broad categories: those aimed at an overall pest population reduction, and others aimed at the protection of a particular crop. In most situations it is now recommended that integrated pest management be used (Bottrell, 1979).
Various cultural practices can be used to kill the different instars, including deep ploughing, discing and other methods of mechanical destruction, manipulation of sowing dates and use of trap crops.
In many areas, natural control of this pest may be quite effective for most of the time. Insect parasitoids attack the eggs (especially Trichogramma spp.) and larvae, and some predators can be important in reducing pest populations. King and Coleman (1989) discuss the prospects for long-term biological control of Heliothis/Helicoverpa spp., and clearly this should be an important component of any regional IPM programme.
The most frequently tried method of achieving biological control has been by augmentative releases of artificially reared parasites or predators, especially using Trichogramma spp. However, releases in cotton have not been consistently effective against heliothine populations. Microplitis croceipes could be more effective because it is less affected by organophosphate pesticides and synthetic pyrethroids.
There has also been interest in exploiting entomophagous pathogens such as Bacillus thuringiensis and Heliothis NPV. In cotton, maize and tomato, transgenic crop varieties expressing the active Bacillus thuringiensis toxin have been used commercially.
A commercial formulation of the nuclear polyhedrosis virus Baculovirus heliothis gave control that was equal to chemical methods. However, the cost of virus applications was higher than chemical control methods. (Martinez and Swezey, 1988).
The development of crop cultivars resistant or tolerant to damage by Heliothis and Helicoverpa spp. has major potential in their management, particularly for communities with few resources. Many crops possess some genetic potential that can be exploited by breeders to produce varieties less subject to pest damage. Resistance can take three basic forms: antixenosis, antibiosis and tolerance. Varieties of crop hosts showing resistance to Heliothis or Helicoverpa have been identified or developed in cotton, chickpeas, soyabean, tomato, maize, sorghum, millet and tobacco.
In maize, resistant genotypes have been identified which have a high concentration of maysin (rhamnosyl-6-C-(4-ketofucosyl)-5,7,3',4'-tetrahydroxyflavone), a C-glycosyl flavone, in silk tissue. Quantitative trait loci for maysin production were identified on chromosomes 1 (p1) and 9 (umc105a) (Byrne et al., 1996).
In cotton, gossypol glands on the calyx crowns of flower buds confers considerable resistance to H. zea (Calhoun et al., 1997).
Transgenic maize containing genes encoding delta-endotoxins from Bacillus thuringiensis (Bt) kurstaki have been commercialized in the USA. Feeding studies using Cry1A(c) toxins demonstrated transformed cotton plants are highly toxic to first-fourth instars of H. zea, but not to fifth instar larvae. Movement of fifth instar larvae from non-Bt plants to Bt-cotton plants in mixed stands could result in feeding and injury to Bt plants (Halcomb et al., 1996). A new type of toxin called vegetative insecticidal proteins (vip) has been isolated from Bacillus thuringiensis during the vegetative phase of growth which shows a wide spectrum of activities against lepidopteran insects, especially noctuids such as H. zea (Estruch et al., 1996).
There is little knowledge of the interactions between natural enemies of Heliothis or Helicoverpa and host-plant resistance, but it cannot be assumed that resistance will always be compatible with natural control. For example, laboratory tests using resistant tomato plants containing an alkaloid (alpha-tomatine) were found to be toxic to Hyposoter exiguae, a parasite of H. zea. The parasite acquired the alkaloid from its host after the host had ingested the alkaloid (Campbell and Duffey, 1979).
Chemical control of the larvae has been the most widely used and generally successful method of pest destruction on most crops, but it is not easy because of larvae feeding within plant structures. The early history of chemical control of corn earworms is given by Hardwick (1965), while COPR (1983) includes a list of 29 insecticides effective for the control of Heliothis/Helicoverpa spp. at the recommended rates given. Pesticide resistance has been known for some years and is quite widespread (Fitt, 1989) especially on cotton crops.
For cotton, chemicals recommended for control include sulprofos, profenofos, thiodicarb, chlorpyrifos, acephate, amitraz and pyrethroids. Several Bacillus thuringiensis sprays are also recommended (Anon., 1997).
For maize, oil applied to silks reduces H. zea damage to the ear. Applications are generally made 3 days after silk emergence and applied on a weekly basis until silk dry down.
Sterile male offspring are produced when certain species are crossed, for example, Heliothis subflexa and H. virescens. This fact has been exploited and evaluated on the island of St Croix, Virgin Islands, where after a 3-year release program, suppression was achieved.
Mating of H. zea was reduced by 50% in a 12 ha maize field treated with hollow fibres containing (Z)-9-tetradecenyl formate (Mitchell and McLaughlin, 1982). Likewise, (Z)-11-hexadecenal, a component of the Heliothis virescens pheromone, reduced the mating of females of H. zea by 85% (Mitchell et al., 1976).
ReferencesTop of page
Anon., 1997. Insect Control Guide. Ohio, USA: Meister Publishing Co., 442 pp.
Balachowsky AS, ed. , 1972. Entomology applied to agriculture. Tome II. Lepidoptera. Second volume. Zygaenoidea-Pyraloidea-Noctuoidea. Entomologie appliquee a l'agriculture. Tome II. Lepidopteres. Deuxieme volume. Zygaenoidea-Pyraloidea-Noctuoidea. Paris, France: Masson et Cie, pp 1059-1634.
Barber GW, 1937. Seasonal availability of food plants of two species of Heliothis in eastern Georgia. Journal of Economic Entomology, 30:150-158.
Bottrell DG, 1979. Guidelines for integrated control of maize pests. FAO, Plant Production and Protection Paper No. 91. Rome, Italy: FAO.
Byrne PF, McMullen MD, Snook ME, Musket TA, Theuri JM, Widstrom NW, Wiseman BR, Coe EH, 1996. Quantitative trait loci and metabolic pathways: genetic control of the concentration of maysin, a corn earworm resistance factor, in maize silks. Proceedings of the National Academy of Sciences of the United States of America, 93(17):8820-8825; 38 ref.
Chiang HC, 1978. Pest management in corn. Annual Review of Entomology, 23:101-123.
COPR, 1983. Pest Control in Tropical Tomatoes. London, UK: COPR.
Davidson RH, Peairs LM, 1966. Insect Pests of Farm, Garden and Orchard (6th edition). New York, USA: Wiley.
EPPO, 1990. Specific quarantine requirements. EPPO Technical Documents, No. 1008. Paris, France: European and Mediterranean Plant Protection Organization.
EPPO, 2014. PQR database. Paris, France: European and Mediterranean Plant Protection Organization. http://www.eppo.int/DATABASES/pqr/pqr.htm
Estruch JJ, Warren GW, Mullins MA, Nye GJ, Craig JA, Koziel MG, 1996. Vip3A, a novel Bacillus thuringiensis vegetative insecticidal protein with a wide spectrum of activities against lepidopteran insects. Proceedings of the National Academy of Sciences of the United States of America, 93(11):5389-5394; 23 refs.
Halcomb JL, Benedict JH, Cook B, Ring DR, 1996. Survival and growth of bollworm and tobacco budworm on nontransgenic and transgenic cotton expressing a CryIA insecticidal protein (Lepidoptera: Noctuidae). Environmental Entomology, 25(2):250-255; 29 ref.
Hardwick DF, 1965. The corn earworm complex. Memoirs of the Entomological Society of Canada, 40:1-247.
Hardwick DF, 1968. A brief review of the principles of light trap design with a description of an efficient trap for collecting noctuid moths. Journal of the Lepidopterists' Society, 22:65-75.
Hardwick DF, 1970. A generic revision of the North American Heliothidinae (Lepidoptera: Noctuidae). Memoirs of the Entomological Society of Canada, 73:1-59.
Heath J, Emmet AM, ed. , 1983. The moths and butterflies of Great Britain and Ireland. Volume 10. Noctuidae (Cuculliinp to Hypeninp) and Agaristidae. The moths and butterflies of Great Britain and Ireland. Volume 10. Noctuidae (Cuculliinp to Hypeninp) and Agaristidae. Harley Books Colchester UK, 459 pp.
King FG, Coleman RJ, 1989. Potential for biological control of Heliothis species. Annual Review of Entomology, 34:53-75.
Kogan M, Helm CG, Kogan J, Brewer E, 1989. Distribution and economic importance of Heliothis virescens and Helicoverpa zea in North, Central, and South America and of their natural enemies and host plants. In: King EG, Jackson RD, eds. Proceedings of the workshop on the biological control of Heliothis: increasing the effectiveness of natural enemies. New Delhi, India: USDA, Far East Regional Office, 241-297.
Marchiori CH, Oliveira AMS, Costa MCR, 2002. Insects collected in maize crop in Itumbiara, south of Goiás state, Brazil. (Insetos coletados em cultivar de milho em Itumbiara, sul de Goiás, Brasil.) Arquivos do Instituto Biológico (São Paulo), 69(Suplemento, Resumos expandidos):233-234. http://www.biologico.sp.gov.br/ARQUIVOS/V69_supl_RE/marchiori.PDF
Martinez R, Swezey SL, 1988. Control of Heliothis zea (Boddie) larvae with a nuclear polyhedrosis virus (Baculovirus heliothis) in cotton, Leon, Nicaragua 1983. Revista Nicaraguense de Entomologia, 2:13-18.
Mitchell ER, Baumhover AH, Jacobson M, 1976. Reduction of mating potential of male Heliothis spp. and Spodoptera frugiperda in field plots treated with disruptants. Environmental Entomology, 5(3):484-486.
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