Striga gesnerioides
(cowpea witchweed)

Pictures

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Identity

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Preferred Scientific Name

• Striga gesnerioides (Willd.) Vatke (1875)

Preferred Common Name

• cowpea witchweed

Other Scientific Names

• Buchnera gesnerioides Willd. (1800)
• Buchnera hydrabadensis Roth. (1821)
• Buchnera orobanchoides R.Br. (1814)
• Striga orobanchoides R.Br. Benth. (1836)

EPPO code

• STRGE (Striga gesnerioides)

Taxonomic Tree

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• Domain: Eukaryota
•     Kingdom: Plantae
•         Phylum: Spermatophyta
•             Subphylum: Angiospermae
•                 Class: Dicotyledonae
•                     Order: Scrophulariales
•                         Family: Orobanchaceae
•                             Genus: Striga
•                                 Species: Striga gesnerioides

Notes on Taxonomy and Nomenclature

Top of page Originally described as Buchnera gesnerioides by Wildenow in 1801, it was independently named B. orobanchoides by R Brown in 1814. In 1836, Bentham used the specific name orobanchoides when creating the new combination Striga orobanchoides which was widely used until quite recently. However, Vatke's combination, using the earlier specific name to make the combination Striga gesnerioides, is now accepted as the more valid.

Description

Top of page S. gesnerioides differs markedly from most other Striga species, in being totally parasitic, without expanded leaves and with a pale-green or yellowish colour. In vigorous plants, as on cowpea, the stems branch mainly below the soil and emerge as a cluster of generally unbranched, fleshy, erect shoots 10-20 cm high, with scale leaves only a few millimetres long (Parker and Riches, 1993). On other hosts, shoots may be single. Much of the shoot comprises the spike-like inflorescence. Flowers, generally in opposite pairs, subtended by bracts 4-6 mm long, are sessile with a tubular calyx, also 4-6 mm long with five ribs and corolla 5-15 mm long with corolla lobes expanding to about 5 mm across. Flower colour in forms attacking cowpea is usually mauve but occasionally white, whereas in other forms it may be reddish, purple or even yellow. The capsule, up to 5 mm long, develops several hundred minute seeds about 0.25 mm long, not readily distinguishable from those of S. asiatica (see Musselman and Parker, 1981). Seed production per plant was estimated to be over 60,000 (Hartman and Tanimonure, 1991).

S. gesnerioides also differs from most other Striga species in developing a substantial haustorium at least several millimetres across, about 1 cm on tobacco and often up to 3-4 cm in diameter on cowpea. The root system is rudimentary.

Chromosome number (2n) = 40.

Distribution

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S. gesnerioides is widely distributed in Africa, from Morocco and Egypt, south to South Africa, also in Arabia and widely in India (up to 2000 m) and Sri Lanka. Holm et al. (1979) indicate occurrence in Australia, but there is no more recent confirmation of this. It also occurs locally in Florida, USA.

A record of S. gesnerioides in Japan (Holm et al., 1979; EPPO, 2014) published in previous versions of the Compendium is unreliable. No original source was provided for the record in Holm et al. (1979). According to Spallek et al. (2013), S. gesnerioides is not present in Japan.

Across most of its range it occurs only on wild hosts. It is only in the western African countries of Senegal, Mali, Togo, Benin, Burkina Faso, Ghana, Nigeria, Niger, Cameroon and Chad that it constitutes a serious weed problem on cowpea. In Zimbabwe, South Africa and Ethiopia it occurs only very locally on tobacco and/or sweet potato.

Distribution Table

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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.

Risk of Introduction

Top of page All Striga species are listed as prohibited imports into Australia, Israel, Russia and USA.

Habitat

Top of page S. gesnerioides is a plant of the semi-arid tropics, associated both with agriculture and with undisturbed natural vegetation. In southern Africa, Hepper (1990) indicates occurrence in Mopane woodland, rocky grassland and cultivated ground. In West Africa, it is apparently able to grow under quite wet conditions but fails to attack aquatic species growing in water 10 cm deep (Porteres, 1948). A survey by Cardwell and Lane (1995) suggested an association of S. gesnerioides with sandy soils.

Habitat List

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Category	Sub-Category	Habitat	Presence	Status
Terrestrial

Hosts/Species Affected

Top of page S. gesnerioides, as a species, has a wide host range, including annual, perennial and woody species, mainly in Dicotyledonae but also some grass species. The main economic host is cowpea, with tobacco and sweet potato also affected very locally. The most commonly affected hosts occur in the families Acanthaceae, Convolvulaceae, Euphorbiaceae, Fabaceae and Solanaceae (Parker and Riches, 1993). Other genera providing occasional hosts, as listed by Porteres (1948) and others, include Sansevieria (Agavaceae), Commiphora (Burseraceae), Cleome (Capparaceae), Helianthus (Asteraceae), Bergia (Elatinaceae), Echinochloa, Panicum, Rottboellia, Brachiaria, Paspalum, Andropogon, Cymbopogon, Hyparrhenia, Oryza, Setaria, Hyparrhenia, Eleusine (Poaceae), Dysophylla (Lamiaceae), Pterodiscus (Pedaliaceae), Cissus (Vitaceae).

Individual biotypes of S. gesnerioides have a much narrower range of hosts, however. The types attacking cowpea are rarely detected on any wild host. An exception is the occurrence of a Nigerian biotype on Indigofera spicata and I. tinctoria as well as cowpea in pot experiments by Igbinnosa and Okonkwo (1991); another type with deeper purple flowers and more slender stems, which overlaps in distribution, attacks Tephrosia (Fabaceae), Jacquemontia and Merremia species (Convolvulaceae). Although the host range of individual biotypes is generally very limited, the hosts attacked by a single biotype may come from diverse plant families. The form occurring in Florida, USA, has only five or six known hosts but these include sunflower (Asteraceae), sweet potato (Solanaceae), Jacquemontia tamnifolia (Convolvulaceae) and Alysicarpus vaginalis (Fabaceae) in addition to the main host Indigofera hirsuta (Fabaceae) (Upton, 1979). Other forms are apparently specific (or nearly so) to tobacco, or to Euphorbia species, while individual biotypes can also differ in the varieties of cowpea that they can parasitize, as noted under Control. These specificities apparently depend on factors involved after attachment, rather than at the germination stage, but the precise mechanisms are not yet fully understood.

References from before 1957, cited here and in other sections, are usefully abstracted in the compilation by McGrath et al. (1957).

Host Plants and Other Plants Affected

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Growth Stages

Top of page Flowering stage, Fruiting stage, Vegetative growing stage

Symptoms

Top of page Symptoms on cowpea are not always obvious in the early stages of infection but show themselves gradually as veinal chlorosis, reduced growth, poor fruiting and eventually chlorosis and withering of foliage. Uprooting reveals the substantial yellowish haustorium, 1-3 cm in diameter at the point of attachment of the Striga plant.

List of Symptoms/Signs

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Biology and Ecology

Top of page The biology of S. gesnerioides is generally very similar to that of S. hermonthica and S. asiatica. It is an obligate parasite with minute seeds, unable to establish without the help of a host plant. Germination depends on a period of moist conditioning and exposure to germination stimulants in host root exudates, the most important of which is alectrol (so named because it also stimulates germination of the related parasite Alectra vogelii) (Muller et al., 1992). This is closely related to the lactones, strigol and sorgolactone, which stimulate S. hermonthica and S. asiatica. S. gesnerioides is also stimulated by ethylene but is relatively insensitive to the strigol analogues GR 7 and GR 24 (Igbinnosa and Okonkwo, 1992; Maass, 1999). Prolonged conditioning in the absence of stimulant results in a secondary 'wet dormancy' (Reid and Parker, 1979; Maass, 1999). Germination temperature appears to be uncritical over the range 23-33°C. Germination is slower than in other species, taking 2-3 days.

Attachment and penetration of the host root do not appear to differ from the other main species (see Reiss and Bailey, 1998), but the physiology of the established parasite differs in showing very low rates of photosynthesis. The effects on the host also differ in that there is no change in root:shoot ratio. Host roots beyond the point of attachment tend to abort. Host photosynthesis may be reduced to some degree but the greatest damaging effect is attributed to the removal of metabolites from the host (Graves et al., 1992; Hibberd et al., 1996). Fertilization is autogamous (Musselman et al., 1991).

A survey by Cardwell and Lane (1995) suggested an association of S. gesnerioides with sandy soils.

Natural enemies

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Notes on Natural Enemies

Top of page S. gesnerioides in West Africa is frequently affected by several gall-forming Smicronyx species, one of which, S. dorsomaculatus, has recently been described as a new species (Anderson and Cox, 1997). The galls caused by Smicronyx species occur variously in the capsules and in the base of the stem. Markham (1985) concluded that stem galls and plant pathogens, including Macrophomina phaseolina, often significantly reduced vigour and seed production of S. gesnerioides in Mali. It has also been noted that use of insecticides in cowpea can result in the destruction of Smicronyx and an increase in vigour of the parasite (Parker and Riches, 1993).

Plant Trade

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Plant parts not known to carry the pest in trade/transport
Bark
Flowers/Inflorescences/Cones/Calyx
Leaves
Roots
Seedlings/Micropropagated plants
Stems (above ground)/Shoots/Trunks/Branches
Wood

Impact

Top of page S. gesnerioides is a severe pest of cowpea across many countries of West Africa, causing significant loss of yield and continuing to spread and intensify in some areas. In a farm survey in the Kano district, northern Nigeria, at least 25% of farmers reported severe infestation of S. gesenerioides in cowpea (Bottenburg, 1995), and Emechebe et al. (1991) reported that many farmers' fields across northern Nigeria had been 'completely blighted'. Ouedraogo (1989) reported a comparable situation in Burkina Faso. In a trial to assess crop loss, yields across a number of cowpea varieties averaged 30% lower and were 56% lower in the most susceptible parasitized by S. gesnerioides (Aggarwal and Ouedraogo, 1989).

Detection and Inspection

Top of page Where infestation is suspected, from previous history or from symptoms of chlorosis, uprooting the crop can reveal the nodules of young Striga seedlings. These can vary in size from a few millimetres to over 2 cm in diameter and are somewhat irregular in shape.

A technique for detecting the seeds of Striga spp. as contaminants of crop seed is described by Berner et al. (1994). This involves sampling the bottom of sacks, elutriation of samples in turbulent flowing water and collection of seeds and other particles on a 90-µm mesh sieve. Striga seeds are then separated from heavier particles by suspension in a solution of potassium carbonate of specific gravity 1.4 in a separating column. Sound seeds collected at the interface are then transferred to a 60-µm mesh for counting. However, the seeds of S. gesnerioides are not readily distinguished from those of other Striga species such as S. asiatica or S. hermonthica (see Musselman and Parker, 1981).

Similarities to Other Species/Conditions

Top of page S. gesnerioides is not readily confused with other Striga species, due to the lack of expanded leaves (see Parker and Riches, 1993, for a key to agriculturally important species).

Prevention and Control

Top of page Cultural Control

No cultural control methods have been widely developed or adopted. Crop rotation should be effective over the long term but is rarely practicable and there has been little research on the potential for trap crops, although pigeon pea, velvet bean (Mucuna species), sorghum and soyabean have been suggested (Wild, 1948; Igbinnosa and Okonkwo, 1991; Berner and Williams, 1998). Cardwell and Lane (1995) also note an apparent absence of S. gesnerioides where cotton is grown. The use of manures or fertilizer to increase soil fertility has apparently much less impact on this species than on those attacking cereal crops (Parker and Riches, 1993). Hand-pulling is difficult and liable to uproot the crop itself, though it should be used where new sporadic infestations are discovered.

Chemical Control

Some herbicides have shown moderate promise for conventional pre-emergence application (see Parker and Riches, 1993), but the farmers affected by S. gesnerioides are not generally in a position to use these and there has been no field use. A more recent development has been the demonstration that S. gesenerioides may be controlled by application of the herbicide imazaquin to the crop seed itself (Berner et al., 1994) but it is uncertain whether this has yet been used in practice.

Biological Control

S. gesnerioides is often very heavily affected by Smicronyx gall-forming weevils and while there has been no attempt to exploit these for biological control it has been noted that this natural control can be adversely affected by insecticide use. The only effort towards biological control has been the testing of the ethylene-generating bacterium Pseudomonas syringae as a means of inducing suicidal germination (Berner et al., 1999). Promising progress in the development of mycoherbicides for control of S. hermonthica, based on Fusarium species, has recently been reported (Watson et al., 2000), and could have relevance for control of S. gesnerioides in the future.

Host-Plant Resistance

The main control measure available for cowpea is varietal resistance. The most important source of resistance is the landrace B301, originally selected for its partial resistance to Alectra vogelii in Botswana (Parker and Riches, 1993). B301 fortunately shows high-level resistance to A. vogelii in West Africa (based on two dominant genes) as well as to S. gesnerioides (based on a single dominant gene) (Singh et al., 1993; Atokple et al., 1995). The resistance, or virtual immunity, of this line has been effective against all biotypes of the parasite in West Africa except that occurring locally in southern Benin. Lane et al. (1996) describe the existence of five known parasite biotypes, varying in their virulence on different 'resistant' varieties of cowpea. Two other sources of resistance, Suvita-2 and IT82D-849, have different single dominant genes for resistance to the Mali biotype, and a different pattern of response to the five parasite biotypes (Atokple et al., 1995). While B301 and IT82D-849 resist four of the known biotypes, Suvita-2 is resistant only in Mali. Fortunately, although each of these three sources is susceptible in southern Benin, other resistant lines, 58-57 and IT81D-994, are resistant to this Benin biotype (Lane et al., 1993) even though they show susceptibility to biotypes in Niger and Nigeria. Further lines with resistance to some biotypes include APL-1 and 87-2 (Moore et al., 1995) but none of these, other than B301, and to some extent IT81D-994, has cross-resistance to Alectra. The mechanisms of resistance are not fully understood but involve a failure of the parasite to develop normally following penetration of the parasite haustorium into the host root (Reiss et al., 1995).

Although B301 is an agronomically poor line, the simple dominance of the resistance character has allowed its ready transfer into more desirable varieties (Singh and Emechebe, 1991). IITA (International Institute for Tropical Agriculture) has now developed lines with resistance to Striga and Alectra, as well as to various other pests and diseases. Singh (1999) lists the most promising of these and indicates that IT90K-76 and IT90K-59, both with resistance from B301, have already been released in Nigeria and South Africa, respectively. Progress is also being made in the development of varieties with combined resistance to Alectra and all five biotypes of S. gesnerioides, using crosses between 58-57 and the B301-derived IT90K-76 (Singh and Emechebe, 1997). In Senegal, Cisse et al. (1995) report a useful degree of resistance in the variety Mouride, whereas the variety KN-1 demonstrates a degree of tolerance, being less damaged in spite of parasite development (Gworgwor, 1991).

Although there has been no evidence as yet for the breakdown of resistance after repeated trials of the varieties based on B301 and other lines, vigilance will be needed to detect any such breakdown and minimize the risks of a build-up of more virulent biotypes. Shawe and Ingrouille (1993) used isoenzyme techniques to demonstrate differences between the populations of S. gesnerioides (from Niger) which emerged on a susceptible variety and on Suvita-2 which is partially resistant to the Niger biotype, emphasizing the risk of selection for virulence in any but totally immune varieties.

References

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Aggarwal VD, Ouedraogo JT, 1989. Estimation of cowpea yield loss from Striga infestation. Tropical Agriculture, 66(1):91-92

Anderson DM, Cox ML, 1997. Smicronyx species (Coleoptera: Curculionidae), economically important seed predators of witchweeds (Striga spp.) (Scrophulariaceae) in sub-Saharan Africa. Bulletin of Entomological Research, 87(1):3-17; 32 ref.

Atokple IDK, Singh BB, Emechebe AM, 1995. Genetics of resistance to Striga and Alectra in cowpea. Journal of Heredity, 86(1):45-49

Berner DK, Awad AE, Aigbokhan EI, 1994. Potential of imazaquin seed treatment for control of Striga gesnerioides and Alectra vogelii in cowpea (Vigna unguiculata). Plant Disease, 78(1):18-23

Berner DK, Cardwell KF, Faturoti BO, Ikie FO, Williams OA, 1994. Relative roles of wind, crop seeds, and cattle in dispersal of Striga spp. Plant Disease, 78(4):402-406; 23 ref.

Berner DK, Schaad NW, V÷lksch B, 1999. Use of ethylene-producing bacteria for stimulation of Striga spp. seed germination. Biological Control, 15(3):274-282; 30 ref.

Berner DK, Williams OA, 1998. Germination stimulation of Striga gesnerioides seeds by hosts and nonhosts. Plant Disease, 82(11):1242-1247; 26 ref.

Bottenberg H, 1995. Farmers' perceptions of crop pests and pest control practices in rainfed cowpea cropping systems in Kano, Nigeria. International Journal of Pest Management, 41(4):195-200; 14 ref.

Cardwell KF, Lane JA, 1995. Effect of soils, cropping system and host phenotype on incidence and severity of Striga gesnerioides on cowpea in West Africa. Agriculture, Ecosystems & Environment, 53(3):253-262

Cisse N, Ndiaye M, Thiaw S, Hall AE, 1995. Registration of 'Mouride' cowpea. Crop Science, 35(4):1215-1216; 1 ref.

Cooke T, 1905. Striga. Bombay Flora, 2(2):302-304.

Emechebe AM, Singh BB, Leleji OI, Atokple IDK, Adu JK, 1991. Cowpea-striga problems and research in Nigeria. Combating striga in Africa: proceedings of the international workshop held in Ibadan, Nigeria, 22-24 August 1988 [edited by Kim, S.K.] Ibadan, Nigeria; International Institute of Tropical Agriculture, 18-28

EPPO, 2014. PQR database. Paris, France: European and Mediterranean Plant Protection Organization. http://www.eppo.int/DATABASES/pqr/pqr.htm

Graves JD, Press MC, Smith S, Stewart GR, 1992. The carbon canopy economy of the association between cowpea and the parasitic angiosperm Striga gesnerioides. Plant, Cell and Environment, 15(3):283-288

GRIN, 2000. Germplasm Resources Information Network. National Genetic Resources Program, ARS, USDA, USA. World Wide Web page at http://www.ars-grin.gov/.

Gworgwor NA, 1991. Studies on the biology and control of Striga. III. Varietal trial of cowpea (Vigna unguiculata) for resistance to Striga gesnerioides. Proceedings of the 5th international symposium of parasitic weeds, Nairobi, Kenya, 24-30 June 1991 [edited by Ransom, J,K,; Musselman, L.J.; Worsham, A.D.; Parker, C.] Nairobi, Kenya; CIMMYT (International Maize and Wheat Improvement Center), 104-107

Hartman GL, Tanimonure OA, 1991. Seed populations of Striga species in Nigeria. Plant Disease, 75(5):494-496

Hepper FN, 1963. Scrophulariaceae. In: Hutchinson J, Dalziel JM, Hepper FN, eds. Flora of West Tropical Africa, Volume 2, second edition. London, UK: Crown Agents, 352-374.

Hepper FN, 1990. 32. Striga Lour. In: Laurent E, Pope GV (eds). Flora Zambesiaca Vol. 8, Part 2. London: Flora Zambesiaca Management Committee, 127-135.

Hibberd JM, Quick WP, Press MC, Scholes JD, 1996. The influence of the parasitic angiosperm Striga gesnerioides on the growth and photosynthesis of its host, Vigna unguiculata. Journal of Experimental Botany, 47(297):507-512; 30 ref.

Holm LG, Pancho JV, Herberger JP, Plucknett DL, 1979. A geographical atlas of world weeds. New York, USA: John Wiley and Sons, 391 pp.

Igbinnosa I, Okonkwo SNC, 1991. Studies on seed germination of cowpea witchweed (Striga gesnerioides) and its effect on cowpea (Vigna unguiculata). Proceedings of the 5th international symposium of parasitic weeds, Nairobi, Kenya, 24-30 June 1991 [edited by Ransom, J.K.; Musselman, L.J.; Worsham, A.D.; Parker, C.] Nairobi, Kenya; CIMMYT (International Maize and Wheat Improvement Center), 58-67

Igbinnosa I, Okonkwo SNC, 1992. Stimulation of germination of seeds of cowpea witchweed (Striga gesnerioides) by sodium hypochlorite and some growth regulators. Weed Science, 40(1):25-28

Lane JA, Moore THM, Child DV, Cardwell KF, 1996. Characterization of virulence and geographic distribution of Striga gesnerioides on cowpea in West Africa. Plant Disease, 80(3):299-301; 11 ref.

Lane JA, Moore THM, Child DV, Cardwell KF, Singh BB, Bailey JA, 1993. Virulence characteristics of a new race of the parasitic angiosperm, Striga gesnerioides, from southern Benin on cowpea (Vigna unguiculata). Euphytica, 72(3):183-188

Maass E, 1999. A comparative study on the germination requirements of some economically important Striga species. PhD Thesis. South Africa: University of Stellenbosch.

Markham RH, 1985. Possibilities for the Biological Control of Striga Species in the Sahel. Nairobi, Kenya: Commonwealth Institute of Biological Control, 16 pp.

M'Boob SS, 1994. Striga in Africa. In: Lagoke STO, Hoevers R, M'Boob SS, Traboulsi, eds. Improving Striga Management in Africa. Proceedings of the 23nd General Workshop of the Pan-African Striga Control Network (PASCON), Nairobi, 1991. Rome, Italy: FAO, 25-29.

McGrath H, Shaw WC, Jansen LL, Lipscomb BR, Miller PR, Ennis WB, 1957. Witchweed (Striga asiatica) - a new parasitic plant in the United States. Plant Disease Epidemics and Identification Section, Agricultural Research Service, United States Department of Agriculture Special Publication, 10.

Moore THM, Lane JA, Child DV, Arnold GM, Bailey JA, Hoffmann G, 1995. New sources of resistance of cowpea (Vigna unguiculata) to Striga gesnerioides, a parasitic angiosperm. Euphytica, 84(3):165-174; 15 ref.

Muller S, Hauck C, Schildknecht H, 1992. Germination stimulants produced by Vigna unguiculata Walp cv. Saunders Upright. Journal of Plant Growth Regulation, 11(2):77-84

Musselman LJ, Bhrathalakshmi, Safa SB, Knepper DA, Mohamed KI, White CL, 1991. Recent research on the biology of Striga asiatica, S. gesnerioides and S. hermonthica. Combating striga in Africa: proceedings of the international workshop held in Ibadan, Nigeria, 22-24 August 1988 [edited by Kim, S. K.] Ibadan, Nigeria; International Institute of Tropical Agriculture, 31-41

Musselman LJ, Hepper FN, 1988. Studies in the flora of Arabia XX: The genus Striga in Arabia. Notes, Royal Botanic Gardens Edinburgh, 45(1):43-50.

Musselman LJ, Parker C, 1981. Surface features of Striga seeds (Scrophulariaceae). Adansonia, 20(4):431-438

Ouedraogo O, 1989. Striga in Burkina Faso. FAO Plant Production and Protection Paper, No. 96:34-36

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Porteres R, 1948. Les plantes indicatrices du niveau de fertilite du complexe cultural edapho-climatique en Afrique tropicale. Agronomie Tropicale (Nogent), 3:246-257.

Reid DC, Parker C, 1979. Germination requirements of Striga spp. Proceedings, Second International Symposium on Parasitic Weeds, North Carolina, 1979., 202-210

Reiss G, Pring RJ, Lane JA, Bailey JA, 1995. Striga gesnerioides: mechanisms of infection and resistance. In: Physiological responses of plants to pathogens. Aspects of Applied Biology, No. 42:301-306.

Reiss GC, Bailey JA, 1998. Striga gesnerioides parasitising cowpea: development of infection structures and mechanisms of penetration. Annals of Botany, 81(3):431-440; 38 ref.

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Shawe KG, Ingrouille MJ, 1993. Isoenzyme analysis demonstrates host selection of parasite pathotypes in the association between cowpea and Striga gesnerioides. Brighton Crop Protection Conference, Weeds, 919-924.

Singh BB, 1999. Striga-resistant cowpeas. Haustorium, 34:4.

Singh BB, Emechebe AM, 1991. Breeding for resistance to Striga and Alectra in cowpea. Proceedings of the 5th international symposium of parasitic weeds, Nairobi, Kenya, 24-30 June 1991 [edited by Ransom, J.K.; Musselman, L.J.; Worsham, A.D.; Parker, C.] Nairobi, Kenya; CIMMYT (International Maize and Wheat Improvement Center), 303-305

Singh BB, Emechebe AM, 1997. 18. Advances in research on cowpea Striga and Alectra. In: Singh BB, Mohan Raj DR, Dashiel KE, Jackai LEN, eds. Advances in Cowpea Research. Ibadan, Nigeria: IITA, 215-224.

Singh BB, Emechebe AM, Atokple IDK, 1993. Inheritance of Alectra resistance in cowpea genotype B 301. Crop Science, 33(1):70-72

Spallek, T., Mutuku, M., Shirasu, K., 2013. The genus Striga: a witch profile., Molecular Plant Pathology, 14(9):861-869 http://onlinelibrary.wiley.com/journal/10.1111/(ISSN)1364-3703

Upton NP, 1979. Striga gesnerioides host tests in Florida. Haustorium, No. 4:3

Watson AK, Ciotola M, Maclean RR, 2000. Striga biocontrol - obstacles overcome? In: Legere A, ed. Abstracts, Third International Weed Science Congress - IWSC, Foz do Iguassu, Brazil, 2000. Brazil: International Weed Science Society, 301.

Wells MJ, Balsinhas AA, Joffe H, Engelbrecht VM, Harding G, Stirton CH, 1986. A catalogue of problem plants in South Africa. Memoirs of the botanical survey of South Africa No 53. Pretoria, South Africa: Botanical Research Institute.

Wild H, 1948. A suggestion for the control of tobacco witchweed (S. gesnerioides (Willd.) Vatke) by leguminous trap crops. Rhodesia Agricultural Journal, 51:330-341.

Links to Websites

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Distribution Maps

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