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Plantwise Technical Factsheet

American cotton bollworm (Helicoverpa zea)

Host plants / species affected
Abelmoschus esculentus (okra)
Abutilon theophrasti (velvet leaf)
Amaranthus (amaranth)
Arachis hypogaea (groundnut)
Brassica oleracea (cabbages, cauliflowers)
Brassica oleracea var. botrytis (cauliflower)
Brassica oleracea var. capitata (cabbage)
Cajanus cajan (pigeon pea)
Capsicum (peppers)
Capsicum annuum (bell pepper)
Chenopodium quinoa (quinoa)
Cicer arietinum (chickpea)
Citrus
Cucumis melo (melon)
Cucumis sativus (cucumber)
Fragaria (strawberry)
Fragaria ananassa (strawberry)
Geranium carolinianum (Carolina geranium)
Gerbera (Barbeton daisy)
Glycine max (soyabean)
Gossypium (cotton)
Helianthus annuus (sunflower)
Ipomoea purpurea (tall morning glory)
Lactuca sativa (lettuce)
Lamium amplexicaule (henbit deadnettle)
Lespedeza juncea var. sericea (Sericea lespedeza)
Lonicera japonica (Japanese honeysuckle)
Medicago lupulina (black medick)
Medicago sativa (lucerne)
Nicotiana tabacum (tobacco)
Panicum miliaceum (millet)
Phaseolus (beans)
Phaseolus vulgaris (common bean)
Salix (willows)
Securigera varia (crown vetch)
Solanum lycopersicum (tomato)
Solanum melongena (aubergine)
Sorghum bicolor (sorghum)
Spinacia oleracea (spinach)
Trifolium (clovers)
Trifolium incarnatum (Crimson clover)
Vicia sativa (common vetch)
Vicia villosa (hairy vetch)
Vigna unguiculata (cowpea)
Zea mays (maize)
Zea mays subsp. mays (sweetcorn)
List of symptoms/signs
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
Symptoms
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.
Prevention and control

Introduction

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).

Cultural Control

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.

Biological Control

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).

Host-Plant Resistance

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

Due to the variable regulations around (de-)registration of pesticides, we are for the moment not including any specific chemical control recommendations. For further information, we recommend you visit the following resources:


Impact
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.
Related treatment support
Plantwise Factsheets for Farmers
CABI; CABI, 2017, Portuguese language
Torres Medina, L.; CABI, 2012, English language
Torres Medina, L.; CABI, 2012, Spanish language
Mayco Toykin, M.; Huanca, F. F.; Oscanoa Rodríguez, C. A.; CABI, Spanish language
Catalan Bazan, W.; Nina Montiel, R.; CABI, Spanish language
 
Pest Management Decision Guides
Thokre, V.; Patkar, N.; Malarvanan, Dr.; Rajkumar, Mr.; CABI, 2014, English language
Castillo, P.; Anibal Ordoñez, J.; CABI, 2013, Spanish language
Castillo, P.; Ordoñez, J. A.; CABI, 2013, Spanish language
Rawlins, T.; CABI, 2014, English language
Ndomba, O.; Kitandu, L.; CABI, 2014, English language
 
External factsheets
CIMMYT Plant Pest and Disease Factsheets, Centro Internacional de Mejoramiento de Maiz y Trigo (CIMMYT) (International Maize and Wheat Improvement Center), English language
Pennsylvania State University Insect Pest Fact Sheets, The Pennsylvania State University, 2001, English language
Pennsylvania State University Insect Pest Fact Sheets, The Pennsylvania State University, 2000, English language
Virginia Cooperative Extension - Agricultural Insects Pests, Virginia Polytechnic Institute and State University, 2003, English language
Bayer CropScience Crop Compendium, Bayer CropScience, English language
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