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Insects - Cowpea

Contributors to this section: IITA, Nigeria (M. Ayodele, L. Kumar).

Contents:
Cowpea aphid
Bean pod borer, Legume pod borer, Cowpea pod borer
Cowpea weevil, Spotted cowpea bruchid, Cowpea seed beetle
Leafhoppers
Bean fly, French bean miner
Flower thrips, Bean flower thrips, African bean thrips

Cowpea aphid

Scientific name

Aphis craccivora

Other scientific names

Aphis medicaginis auct. nec. Koch, 1854
Aphis leguminosae Theobald, 1915
Pergandeida craccivora Koch

Importance

High

Significance

This Aphid is a major economic pest of cowpea. The aphid while feeding removes sap from the leaves, pods, seeds and other aerial plant parts causing damage to the plant resulting in yield reductions.
From experimental data and results, infestation with A. craccivora caused significant reductions in seed yield. (Ofuya, 1989). In a Chinese study A. craccivora infestation, resulted in a reduction in plant height to 41.9% , green leaf area and delayed production of harvestable pods by 30 days (Chang and Thrower, 1981).
Infestations of A. craccivora on cowpeas caused reduction in growth and losses in yield (Annan et al., 1995). Attia et al., (1986). Bishara et al., (1984), reported that A. craccivora was the most damaging pest of cowpeas in Egypt, particularly early in the growing season.
In addition to loss due to damage caused by the aphid, A. craccivora is known to be an important vector of plant viral disease, transmitting over 30 plant viruses, (Wightman and Wightman, 1994).
The aphid also produces honeydew, a substrate which attracts fungi (Mayeux, 1984).

Symptoms

The aphids attacks all growing stages and parts of the plant : flowering, seedling and vegetative growing , points including the leaves and the plant as a whole.

Leaves: distortion, stunting of leaflets, lesions; abnormal colours; premature defoliation; sooty mould

Pod : shrivelling. (Ofuya, 1995; Bottenberg et al., 1998).

Growing points: rosette

Seed : shrivelling

Whole plant : stunting, deformities and yield reductions. (Annan et al., 1997)

Infested cowpea plant (photo:IITA)

Aphids
(photo:IITA)

Hosts

The insect feeds on several plants causing damage. Some reported hosts are Vigna unguiculata (cowpea), Arachis hypogaea (groundnut), Cajanus cajan (pigeon pea), Medicago sativa (lucerne), Vigna radiata (mung bean), Capsicum (peppers), Chenopodium quinoa (quinoa), Cicer arietinum (chickpea), Citrus , Gossypium (cotton), Lablab purpureus (hyacinth bean), Lupinus (lupins), Lycopersicon esculentum (tomato), Phaseolus (beans), Phaseolus vulgaris (common bean), Sesamum indicum (sesame), Solanum tuberosum (potato), Theobroma cacao (cocoa), Trifolium (clovers), Vicia faba (broad bean), Vigna catjang , Vigna mungo (black gram).

Geographic distribution

World wide in distribution. It has been reported in Europe, Asia, Africa, Central America, Canada, Mexico, USA, Argentina, Bolivia, Brazil, Chile, Venezuela, Australia, Fiji, New Zealand.

Biology and transmission

Is a shiny black aphid, feeding on the undersurface of the cowpea leaves ,young stems an pods.

Parthenogenetic reproduction occurrs all year round. The aphid is ovoviviparous, The females retain eggs inside their bodies and give birth to small larvae.Young colonies of this small aphids are found on growing points of plants in association with ants. (Soans and Soans, 1971; Patro and Behera, 1991).

Although A. craccivora is polyphagous, it has preference for Leguminosae.

 A. craccivora is dispersed by wind. ( dispersal of the winged forms).

Detection/indexing methods used at IITA

Field inspection during active growth and in storage

Dry seed inspection:

Treatment

Chemical pesticides used for the control of the aphid and ants on the field during active growth:

Chemical control

Protocol

Cultural

Procedures in case of positive test at IITA

References and further reading

Annan IB, Schaefers GA, Tingey WM. 1995. Influence of duration of infestation by cowpea aphid (Aphididae) on growth and yield of resistant and susceptible cowpeas. Crop Protection, 14(7):533-538.

Annan IB, Ampong-Nyarko K, Tingey WM, Schaefers GA. 1997. Interactions of fertilizer, cultivar selection, and infestation by cowpea aphid (Aphididae) on growth and yield of cowpeas. International Journal of Pest Management, 43(4):307-312.

Attia AA, El-Heneidy AH, El-Kady EA. 1986. Studies on the aphid, Aphis craccivora, Koch. (Homoptera: Aphididae) in Egypt. Bulletin de la Société Entomologique d’égypte, No. 66:319-324.

Bishara SI, Fam EZ, Attia AA, El-Hariry MA. 1984. Yield losses of faba bean due to aphid attack. FABIS Newsletter, Faba Bean Information Service, ICARDA, No. 10:16-18.

Bottenberg H, Tamò M, Singh BB. 1998. Occurrence of phytophagous insects on wild Vigna sp. and cultivated cowpea: comparing the relative importance of host-plant resistance and millet intercropping. Agriculture, Ecosystems & Environment, 70(2/3):217-229

Mayeux A. 1984. The groundnut aphid. Biology and control. Oléagineux, 39(8/9):425-434; [

Ofuya TI. 1989. The effect of pod growth stages in cowpea on aphid reproduction and damage by the cowpea aphid, Aphis craccivora (Homoptera: Aphididae). Annals of Applied Biology, 115(3):563-566.

Patro B, Behera MK. 1991. Mutualism between the bean aphids (Aphis craccivora Koch) and ants. Orissa Journal of Agricultural Research, 4(3-4):238.

Soans AB, Soans JS. 1971. Proximity of the colonies of the tending ant species as a factor determining the occurrence of aphids. Journal of the Bombay Natural History Society, 68(3):850-851

Wightman JA, Wightman AS. 1994. An insect, agronomic and sociological survey of groundnut fields in southern Africa. Agriculture, Ecosystems & Environment, 51(3):311-331.

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Bean pod borer, Legume pod borer, Cowpea pod borer

Scientific name

Maruca vitrata

Other scientific names

Maruca testulalis Geyer
Crochiphora testulalis Geyer

Importance

High

Significance

Loss in yield not quantified but it is a major cowpea pest in Nigeria .(Odulaja and Oghiakhe 1993).

Symptoms

Maruca  feeds on the tender stems, flower buds, flowers, peduncles, pods, and leaves causing damage to all the plant parts. Symptoms found on:

Flowers: round holes,

Leaves: holes

Pods: distortion

Hosts

The insect attacks 39 hosts of which 37 are leguminous as reported by Rathore and Lal (1998). Arodokoun (1996) listed 23 host plants of M. vitrata in Benin Republic. Some recorded hosts of concern to peasant farmers in the tropics include Vigna unguiculata (cowpea), Cajanus, Cajanus cajan (pigeon pea), Canavalia, Canavalia ensiformis (gotani bean), Fabaceae (leguminous plants), Glycine, Lablab purpureus (hyacinth bean), Phaseolus (beans), Phaseolus lunatus (lima bean), Phaseolus vulgaris (common bean) and Pueraria phaseoloides (tropical kudzu).

Geographic distribution

Belgium, Denmark, France, UK, Asia, China, India, Indoneia, Iran, Japa, Korea, Malaysia, Nepal, Sri Lanka, Thailand, Singapore, Vietnam, Africa, Central America, Mexico, USA, S. America, Australia, Fiji, Papua New Guinea.

Biology and transmission

Adults are not active during the day. They are usually found at rest under the lower leaves of the host plant. They live for an average of 6-10 days, each female laying   up to 200 eggs. Ke et al. (1985) recorded seven generations per year in China.

Detection/indexing methods used at IITA

Field inspection during active growth and inspection during storage

Dry seed inspection

Treatment

Chemical control

Procedures in case of positive test at IITA (Discard)

References and further reading

Arodokoun DY. 1996. Importance des plantes-hotes alternatives et des ennemis naturels indigenes dans le controle biologique de Maruca testutalis Geyer (Lepidoptera, Pyralidae), ravageur de Vigna unguiculata Walp. PhD thesis. Quebec, Canada: Universite Laval, 182.

Ke LD, Fang JL, Li ZJ. 1985. Bionomics and control of the legume pod-borer Maruca testulalis Geyer. Acta Entomologica Sinica, 28(1):51-59.

Odulaja A, Oghiakhe S. 1993. A nonlinear model describing yield loss in cowpea (Vigna unguiculata) due to the legume pod borer, Maruca testulalis Geyer (Lepidoptera: Pyralidae). International Journal of Pest Management, 39(1):61-63.

Rathore YS, Lal SS. 1998. Phylogenetic relationship of host plants of Maruca vitrata.

Indian Journal of Pulses Research, 11(2):152-155.

Singh, S R. 1977. Grain legume Entomology, IITA, Ibadan, Nigeria., 55 pp.

Adult on cowpea (photo:IITA)

Larva stage (photo:IITA)

Pupa stage (photo:IITA)

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Cowpea weevil, Spotted cowpea bruchid, Cowpea seed beetle

Scientific name

Callosobruchus spp.

Other scientific names

Bruchus quadrimaculatus Fabricius 1792
Callosobruchus ornatus (Boheman 1829)

Importance

High

Significance

In Nigeria, yield loss was estimated to 3% of the annual production in 1961/62 . Infestation starts in the pods in the field and are carried over into storage where infestation continues and substantial losses occur (Ojimelukwe et al., 1999). Decrease seed /grain quality.

Symptoms

The insect attacks the fruiting stage, seeds and all stored grains and products.

Pod : eggs cemented to the surface.

Seeds : Round holes.

Hosts

C. maculatus is a major pest of cowpeas, green gram and lentils).
The hosts attacked are Vigna unguiculata (cowpea), Acacia nilotica (gum arabic tree), Cajanus cajan (pigeon pea), Glycine max (soyabean), Phaseolus (beans), stored products (dried stored products), Vigna radiata (mung bean), and Voandzeia subterranea (bambara groundnut).

Geographic distribution

C. maculatus is widely distributed throughout the tropics and sub-tropics. It is found in China, India, Iran, Pakistan, Sri Lanka, Turkey, Africa, Nicaragua, USA, Brazil, Peru, Venezuela, Australia.

Biology and transmission

Adult Callosobruchus maculatus do not feed on stored products. Short lived having a life span of no more than 12 days. Females lay many eggs up to 115 eggs.The beettle lays eggs on maturing cowpea pods.

Detection/indexing methods used at IITA

Field inspection during active growth and inspection of stored seeds for conservation

Dry seed inspection:

Treatment/cControl

Cultural

Procedures in case of positive test at IITA

References and further reading

Ojimelukwe PC, Onweluzo JC, Okechukwu E. 1999. Effects of infestation on the nutrient content and physicochemical properties of two cowpea (Vigna unguiculata) varieties. Plant Foods for Human Nutrition, 53(4):321-332.

Cowpea weevil, Source Ayodele/Oguntade (IITA)

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Leafhoppers

Scientific name

Empoasca spp.

Other scientific name

Empoasca dolichi

Importance

High

Significance

Not reported.

Symptoms

Emposca attacks cowpea seedlings causing

Leaves :discoloration of veins and margins, cupping

Whole plant : stunting, pre mature drying of the plant.

Empoasca dolichi (photos: IITA)

Hosts

The leaf hoppers attack Vigna unguiculata (cowpea), Arachis hypogaea (groundnut), and Gossypium (cotton).

Geographic distribution

Africa, Nigeria

Biology and transmission

The hopper lays eggs on the underside of the leaves. Adults expentancy life varies from 30-60 days.

Detection/indexing methods used at IITA

Field inspection during active growth

Dry seed inspection

Treatment/control

Cultural

Chemical control, applying sprays during active growth with either:

Protocol

Procedures in case of positive test at IITA

References and further reading

Singh SR. 1977. Grain Legume Entomology,IITA, Ibadan, Nigeria,., 55pp

Singh SR. 1977. Tropical Grain Legume Bull.9.1-7

Singh RS, van Emden HF. 1998. Ann.Rev. Entom., 24, Rev, 255-278

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Bean fly, French bean miner

Scientific name

Ophiomyia phaseoli

Other scientific names

Melanagromyza phaseoli Vanschuytebroeck, 1951
Agromyza phaseoli Coquillett, 1899
Agromyza destructor Malloch, 1916

Importance

High

Significance

The bean fly is a serious and destructive pest of cow pea and other edible legumes in the tropical and subtropical regions of Asia Talekar (1990.

In Tanzania yield loss which ranges from 30-50% were reported by Wallace, (1939; Walker, (1960). Also, in 1985, the Asian Vegetable Research and Development Center (AVRDC), reported that in Taiwan damage caused by the fly reduced cowpea yield by 32%.

Symptoms

Symptoms caused by the fly are exhibited on various plant parts where they feed and lay eggs,

Leaves : punctures on the upper side, light yellow spots, larval mines turn dark brown, blotchy and drooping, defoliation

Trifoliate leaves : egg holes, silvery, curved stripes of larval mines which are visible on the underside of the leaves , visible tunnels on the upper side of the leaves.

Leaf petiole : swollen

Root : tunnelling , cortex destruction, swollen

Stem : Tunnelling

Whole plant : stunting , Wilting

Hosts

Vigna unguiculata (cowpea) has been reported as a minor host of this fly. Listed major hosts are Fabaceae (leguminous plants), Phaseolus (beans), Phaseolus vulgaris; (common bean), Vigna radiata (mung bean). Minor and wild hosts of the fly have also been reported which include: Cajanus cajan (pigeon pea), Glycine max (soyabean), Phaseolus lunatus (lima bean), Pisum sativum (pea), Psophocarpus tetragonolobus (winged bean), Vigna angularis (adzuki bean), and Vigna mungo (black gram).

Geographic distribution

Bangladesh, China, India, Indonesia, , Iran, Israel, Japan, Jordan, Malaysia, Nepal, Pakistan, Singapore, Saudi Arabia, Sri Lanka, Thailand, Vietnam, Africa, USA, Australia, Fiji, Papua New Guinea

Biology and transmission

The famales of the bean fly are very active on warm clear days seeking young tender leaves for oviposition.  Eggs are laid during the morning hours on the upper side of the leaves, often near the midrib close to the petiole.

Burikam (1980) reported that females lay an average of 77 eggs in cowpea. The adult females live for 23-42 days and males for 31-38 days, and if no food is provided they die in 2-3 days ( Raros (1975) .

Detection/indexing methods used

Field inspection during active growth

Dry seed inspection

Treatment/control

Cultural

Chemical control

Protocol

Procedures in case of positive test at IITA

References and further reading

AVRDC. 1985. 1983 Progress report. Shanhua, Taiwan: Asian Vegetable Research and Development Center

Burikam I. 1978. Ecological investigation of the bean fly, Ophiomyia phaseoli (Tryon) (Diptera: Agromyzidae) and its natural enemies in Thailand., 71 pp.; [24 fig., unpublished M.Sc. thesis]

Raros ES. 1975. Bionomics of bean fly, Ophiomyia phaseoli (Tryon) (Diptera: Agromyzidae) and its parasites in Hawaii. Ph. D. Thesis. Honolulu, USA: Department of Entomology, University of Hawaii.

Talekar NS. 1990. Agromyzid flies of food legumes in the tropics. New Delhi, India: Wiley Eastern Limited

Walker PT. 1960. Insecticide studies in East African agricultural pests. III. Seed dressing for the control of beanfly, Melanagromyza phaseoli (Coq.) in Tanganyika. Bulletin of Entomological Research, 50:781-793.

Wallace GB. 1939. French bean diseases and bean fly in East Africa. East African Agricultural Journal, 5:170-175.

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Flower Thrips, Bean flower thrips, African bean thrips

Scientific name

Megalurothrips sjostedti Trybom, 1908.

Other scientific names

Taeniothrips sjostedti Trybom
Lundathrips inopinatus Bournier, 1979.

Importance

High

Significance

These Thrips are responsible for the total cowpea yield loss in West Africa

 Serious infestation causing the loss of flower resulting to complete loss of yield was reported by   Childers and Achor, (1995). Alghali (1992) reported that in Nigeria, yield loss of cowpeas was up to 75% when insects attacked during the flower budding and flowering stages.

Symptoms

The Thrips attack the flowering stage infesting the inflorescence and leaves.
Childers and Achor, ( 1995) reported that feeding by M. sjostedti which begins before the flowers open, damages various parts of the cowpea plant especially the flowers. Infestation of the flower and other plant parts results to:

Inflorescence: distortion and discolouration, abortion, reduced pollen production and flower loss

Leaves: Defoliation

Whole plant : death, yield reduction

Megalurothrips sjostedti(photos:IITA)

Hosts

Legumes are the main hosts of M. Sjostedti and this include Vigna unguiculata (cowpea), Cajanus cajan (pigeon pea), Phaseolus vulgaris (common bean). Tamo et al. (1993b).They also attack some other plants considered as minor hosts such as Arachis hypogaea (groundnut), and some wild hosts.

Geographic distribution

Reported to be found throughout Sub-Saharan Africa, from the high rainfall areas of West to the semi-arid areas of Kenya and Sudan. Meanwhile in Nigeria, it is associated with the dry savanna regions in which cowpeas are produced.

Biology and transmission

Rapid breeding, laying eggs on leaf petioles, peduncles , inflorescences and  pods was reported by Tamo et al., (1993a). Salifu, (1992) reported that development from egg to adult takes about 19 days at 29°C and 58% RH and adults live for about 23 days.

Taylor (1969) reported that the infestation of cowpea plants begin just before flowering. That the adults fligh by day, with the peak of flight activity occurring between noon and 1 pm at a temperature 23-24°C. It had been observed that, both temperature and light intensity influence flight.

Detection/indexing methods used at IITA

Field inspection during active growth.

Dry seed inspection:

Treatment

Cultural

Chemical control, applying sprays during active growth with any of the pesticides

Protocol

Biological control

Procedures in case of positive test at IITA

References and further reading

Alghali AM. 1992. Insecticide application schedules to reduce grain yield losses caused by insects of cowpea in Nigeria. Insect Science and its Application, 13(5):725-730

Childers CC, Achor DS. 1995. Thrips feeding and oviposition injuries to economic plants, subsequent damage and host responses to infestation. In: Parker BL, et al., eds. Thrips Biology and Management. New York, USA: Plenum Press.

Salifu AB. 1992. Some aspects of the biology of the bean flower thrips Megalurothrips sjostedti (Trybom) (Thysanoptera: Thripidae) with reference to economic injury levels on cowpea (Vigna unguiculata (L.) Walp). Revue de Zoologie Africaine, 106(5):451-459.

Tamò M, Baumgärtner J, Arodokoun DY. 1993. The spatio-temporal distribution of Megalurothrips sjostedti (Trybom) (Thysanoptera, Thripidae) life stages on cowpea, and development of sampling plans. Mitteilungen der Schweizerischen Entomologischen Gesellschaft, 66(1-2):15-34.

Tamò M, Baumgärtner J, Delucchi V, Herren HR. 1993. Assessment of key factors responsible for the pest status of the bean flower thrips Megalurothrips sjostedti (Thysanoptera: Thripidae) in West Africa. Bulletin of Entomological Research, 83(2):251-258

Taylor TA. 1969. On the population dynamics and flight activity of Taeniothrips sjostedti (Tryb.) (Thysanoptera:Thripidae) on cowpea. Bulletin of the Entomological Society of Nigeria, 1969:60-71.

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The Genebanks

The 11 CGIAR genebanks currently conserve 730,000 of cereals and grain legumes, forage crops, tree species, root and tuber crops, bananas and crop wild relatives.

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