Scutellonema bradys (yam nematode)
- 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
- Seedborne Aspects
- Pathway Vectors
- Plant Trade
- Detection and Inspection
- Prevention and Control
- Distribution Maps
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PicturesTop of page
IdentityTop of page
Preferred Scientific Name
- Scutellonema bradys (Steiner & Le Hew, 1933) Andrássy, 1958
Preferred Common Name
- yam nematode
Other Scientific Names
- Anguillulina bradys (Steiner & Le Hew, 1933) T. Goodey, 1975
- Hoplolaimus bradys Steiner & Le Hew, 1933
- Rotylenchus blaberus Steiner, 1937
- Rotylenchus bradys (Steiner & Le Hew, 1933) Filipjev, 1936
- Scutellonema blaberum (Steiner, 1937) Andrássy, 1958
- Scutellonema dioscorea Lordello, 1959
International Common Names
- English: yam dry rot nematode
- French: nématode de l'igname
- SCUNBR (Scutellonema bradys)
Taxonomic TreeTop of page
- Domain: Eukaryota
- Kingdom: Metazoa
- Phylum: Nematoda
- Family: Hoplolaimidae
- Genus: Scutellonema
- Species: Scutellonema bradys
Notes on Taxonomy and NomenclatureTop of page
DescriptionTop of page
15 Female (syntypes): L=0.88-1.11 mm; a=27-32; b=6.7-8.7; b'=5.2-6.0; c=32-56; V = 54-59; spear = 26-30 µm.
10 Male (T. Goodey's specimens from Nigerian yam): L=0.85-1.0 mm; a=26-36; b=6.6-9.0; b'=5.2-6.6; c=27-32; spear=25-28 µm; spicules=29-33 µm; gubernaculum=14-17 µm.
Female (based on syntypes): Body straight to slightly arcuate when relaxed; annules about 1.6 µm wide near middle; lateral fields about one-fifth body-width, with 4 incisures, areolated at phasmids and anteriorly, sometimes irregularly areolated on mid-body and tail. Lip region knob-like, offset by a constriction, with a labial disc and 6 to 8 (usually 7) annules lacking longitudinal striations. Cephalic sclerotization strong. Spear well developed with large oval to rounded basal knobs bearing flattened, indented or irregular anterior surfaces; anterior tapering portion a little less than half spear length. Hemizonid usually distinct, 2-3 annules long, 0-3 annules anterior to excretory pore and close to oesophago-intestinal junction. Hemizonion 1 annule long, about 8 annules behind the excretory pore. Oesophageal glands elongate, overlapping intestine dorsally and dorso-laterally; nucleus of dorsal gland anterior to those of subventrals. Ovaries paired, with oocytes in 1 or 2 rows. Spermathecae rounded, sometimes oval, usually packed with sperms. Vulva a transverse slit with conspicuous cuticular thickenings towards ends (? = 'vaginal glands' of Sher, 1964). Epiptygma inconspicuous. Intestine partially overlapping rectum. Tail variable with obtusely rounded striated terminus and 13 - 20 annules. Phasmids about 4 µm diameter, with pore-like aperture, at or up to 6 annules anterior to anal level (Siddiqi, 1972).
Male: Abundant. Similar to female except for sexual dimorphism. Testis outstretched; spermagonia in 3-4 rows; sperms about 4 µm in diameter. Bursa large, crenate, enclosing tail. Spicules slightly cephalated and ventrally arcuate, with large distal flanges. Capitulum (= telamon) prominent, about 10 µm long. Phasmids usually just postanal. Cuticular, non-protoplasmic terminal portion of tail 11-16 µm long (Siddiqi, 1972).
DistributionTop of page
A record of S. bradys on yam in Korea (CABI/EPPO, 2000; EPPO, 2006) published in previous editions of the Compendium has been removed as it was based on a misidentification. Although S. bradys was reported in yam fields of Geyongbuk province, Korea in 1998 (Park et al., 1998), it was not supported with morphometric data or a description of the species. S. bradys was not found in 160 soil samples taken during a survey of major yam-growing regions of Geyongbuk province in 2006 (Park and Khan, 2007).
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.Last updated: 30 Jun 2021
|Continent/Country/Region||Distribution||Last Reported||Origin||First Reported||Invasive||Reference||Notes|
|South Korea||Absent, Invalid presence record(s)|
|Trinidad and Tobago||Present|
|United States||Present, Localized|
Risk of IntroductionTop of page
Hosts/Species AffectedTop of page
Two wild Dioscorea spp. growing in forests in Nigeria and Cameroon have been shown to be natural hosts (Bridge, 1982; Bridge et. al., 1995).
A wide range of other crops and some weeds have been shown to support low root populations of S. bradys including yam bean (Pachyrrhizus erosus), greengram (Phaseolus aureus), pigeon pea (Cajanus cajan), kenaf (Hibiscus cannabinus), okra (Hibiscus esculentus), tomato (Lycopersicon esculentum), sorghum (Sorghum vulgare), loofah (Luffa cylindrica), roselle (Hibiscus sabdariffa) and Synedrella nodiflora. These alternative hosts permit the yam nematode to survive in soil in the absence of yams, but only cowpea (Vigna unguiculata), melon (Cucurbita melo) and sesame (Sesamum indicum) in addition to yams have been found to actually increase populations of the nematode (Luc and de Guiran, 1960; Adesiyan 1976; Bridge, 1982; Jatala and Bridge, 1990).
Host Plants and Other Plants AffectedTop of page
Growth StagesTop of page
SymptomsTop of page
List of Symptoms/SignsTop of page
|Roots / necrotic streaks or lesions|
|Vegetative organs / dry rot|
|Vegetative organs / internal rotting or discoloration|
|Vegetative organs / surface cracking|
Biology and EcologyTop of page
In yams, S. bradys invades the young, developing tubers through the tissues of the tuber growing point, alongside emerging roots and shoots, through roots and also through cracks or damaged areas in the tuber skin (Bridge, 1972). Nematodes feed intracellularly in yam tuber tissues resulting in rupture of cell walls, loss of cell contents and the formation of cavities (Goodey, 1935; Bridge, 1973; Adesiyan et al., 1975a). They are mainly confined to the sub-dermal, peridermal and underlying parenchymatous tissues in the outer 1-2 cm of tuber. S. bradys continues to feed and reproduce in yams stored after harvesting. Populations can increase 9 to 14-fold in D. rotundata tubers over a 5 to 6 month storage period, and 5 to 8-fold in D. alata and D. cayenensis respectively over the same period (Bridge, 1973; Adesiyan, 1977). In tubers with partial dry rot, more nematodes are found in the oldest, apical portions, adjacent to the stems (Adesiyan, 1977).
Seedborne AspectsTop of page
Pathway VectorsTop of page
Plant TradeTop of page
|Plant parts liable to carry the pest in trade/transport||Pest stages||Borne internally||Borne externally||Visibility of pest or symptoms|
|Bulbs/Tubers/Corms/Rhizomes||adults; eggs; juveniles||Yes||Pest or symptoms not visible to the naked eye but usually visible under light microscope|
|Growing medium accompanying plants||adults; eggs; juveniles||Yes||Pest or symptoms not visible to the naked eye but usually visible under light microscope|
|Roots||adults; eggs; juveniles||Yes||Yes||Pest or symptoms not visible to the naked eye but usually visible under light microscope|
|Seedlings/Micropropagated plants||adults; eggs; juveniles||Yes||Pest or symptoms not visible to the naked eye but usually visible under light microscope|
|Plant parts not known to carry the pest in trade/transport|
|Fruits (inc. pods)|
|Stems (above ground)/Shoots/Trunks/Branches|
|True seeds (inc. grain)|
ImpactTop of page
DiagnosisTop of page
Detection and InspectionTop of page
Prevention and ControlTop of page
Due to the variable regulations around (de)registration of pesticides, your national list of registered pesticides or relevant authority should be consulted to determine which products are legally allowed for use in your country when considering chemical control. Pesticides should always be used in a lawful manner, consistent with the product's label.Introduction
Management of S. bradys can be achieved by one or more of the following measures: (1) controlling nematodes in field soil by cultural or chemical means (2) use of planting material that is naturally free of nematodes, or treatment of seed material (tubers and setts with yams) prior to planting to reduce or eliminate nematodes from propagative material, and (3) in the case of yams, treatment of tubers after harvesting to prevent storage losses (Jatala and Bridge, 1990).
In Field Soil
In Cuba, keeping fallow land free of all host plants is a suggested means of reducing damage by S. bradys to yams (Decker et al., 1967) but this is unlikely to be economic or practical in most situations. Yams are frequently intercropped, sometimes with as many as five other crops (Coursey, 1967). Control of weed hosts and the exclusion of other crop hosts of S. bradys from around yams will help to reduce nematode damage. Soil populations of S. bradys will be reduced if a non-host or poor host crops, such as groundnut, chilli pepper, tobacco, Indian spinach (Beta vulgaris var. benghalensis), cotton, maize or sorghum are grown prior to yams (Adesiyan, 1976).
Application of chemical nematicides has, at best, only produced moderate yield increases and control of S. bradys (Anon., 1964; Ayala and Acosta, 1971) and information on the economics of this means of control is lacking for large scale use.
Resistance to S. bradys in yams has yet to be confirmed and all the main food yams (D. alata, D. bulbifera, D. cayenensis, D. esculenta, D. rotundata) are susceptible to damage. However, resistance could prove to be the most practical and economic means of managing S. bradys if found in commercially acceptable cultivars.
Clean Planting Material
In yams, using nematode-free planting material is a practical and economic means of preventing damage by S. bradys and also their dissemination. Seed tubers showing symptoms of dry rot (cracking and flaking) should not be used for planting. The presence of dry rot in tubers without external symptoms can be determined by scraping away sections of tuber skin, or by the use of tuber pieces rather than whole tubers enabling the grower to examine for dry rot symptoms before planting.
Bulbils or aerial tubers of the yam D. bulbifera and some forms of D. alata, which are used for propagation will be completely free of nematodes. A number of yams, such as D. alata, D. rotundata and D. dumentorum, can be produced from vine cuttings (Coursey, 1967). Even true seed can be used for propagating D. rotundata (Sadik and Okereke, 1975). Although these methods of propagation are not a practical means of producing ware tubers, they can be used to produce nematode-free seed tubers (Jatala and Bridge, 1990). The use of 'microsetts' or 'minisetts' cut from mature tubers (International Institute of Tropical Agriculture, 1984) can provide clean planting material if the mother seed yams selected are free of nematodes.
Some traditional practices in Africa, such as the use of wood ash on yam tubers or mixing cow dung in yam mounds before planting are reported to decrease nematode numbers (Adesiyan and Adeniji, 1976).
Hot water treatment can reduce or eliminate S. bradys from yam tubers. The expense of heating equipment, and the difficulties of maintaining constant temperatures, are the main prohibitive factors against its large scale use. However, it is feasible for small scale operations and for establishing nematode-free planting material. Most studies have shown that a water temperature of 50-55°C for up to 40 min gives the best control of S. bradys without damaging tubers (Jatala and Bridge, 1990).
ReferencesTop of page
Addoh PG, 1971. The distribution and economic importance of plant parasitic nematodes in Ghana. Ghana Journal of Agricultural Science, 4:21-32.
Adesiyan SO; Odihirin RA; Adeniji MO, 1975. Histopathology studies of the yam tuber (Dioscorea rotundata Poir) infected with Scutellonema bradys (Steiner & Le Hew). Internatonal Biodeterioration Bulletin, 11:48-55.
Anon., 1964. Nematode control trials with yam. Annual Report for the Ministry of Agriculture Nigeria for 1962-63.
Ayala A; Acosta N, 1971. Observations on yam (Dioscorea alata) nematodes. Nematropica, 1:39-40.
Baimey H; Coyne D; Labuschagne N, 2009. Pathogenicity of Scutellonema bradys populations from different geographical areas in Benin on yam (Dioscorea spp.). Crop Protection, 28(9):715-721. http://www.sciencedirect.com/science/journal/02612194
Baimey, H., Coyne, D., Labuschagne, N., 2006. Effect of fertiliser application on yam nematode (Scutellonema bradys) multiplication and consequent damage to yam (Dioscorea spp.) under field and storage conditions in Benin. International Journal of Pest Management, 52(1), 63-70. doi: 10.1080/09670870600552380
Baudin P, 1956. Les maladies parasitaire des ignames en Côte d'Ivoire. Revue de Mycologie, Paris, 21(2):87-111.
Bridge J, 1972. Nematode problems with yams (Dioscorea spp). PANS, 1:89-91.
Bridge J, 1973. Nematodes as pests of yams in Nigeria. Mededelingen Fakulteit Landbouwwetenschappen, 38:841-852.
Cadet, P., Daly, P., 1996. Use of nematicides to produce yam planting material free of Scutellonema bradys in Martinique (French West Indies). Crop Protection, 15(2), 187-195. doi: 10.1016/0261-2194(95)00125-5
Coimbra JL; Almeida NSde; Garrido Mda S; Soares ACF; Sousa Cda S; Carmo DOdo, 2006. Plant parasitic nematodes associated with exotic and native fruit trees in the Reconcavo Region of the State of Bahia, Brazil. (Nematóides fitoparasitos associados a fruteiras nativas e exóticas na região do Recôncavo da Bahia, Brasil.) Magistra, 18(1):48-51. http://www.magistra.ufba.br/
Coursey DG, 1967. Yams. London, UK: Longmans.
Coyne DL; Kolombia YA; Kariuki G; Luambano N; Bert W, 2016. First report of dry rot disease of yam caused by Scutellonema bradys in East Africa. Plant Disease, 100(8):1794. http://apsjournals.apsnet.org/loi/pdis
Coyne, D. L., Tchabi, A., Baimey, H., Labuschagne, N., Rotifa, I., 2006. Distribution and prevalence of nematodes (Scutellonema bradys and Meloidogyne spp.) on marketed yam (Dioscorea spp.) in West Africa. Field Crops Research, 96(1), 142-150. doi: 10.1016/j.fcr.2005.06.004
Coyne, D., Claudius-Cole, A., 2009. Scutellonema bradys, the yam nematode, newly reported affecting Irish potato (Solanum tuberosum) in Nigeria. Plant Pathology, 58(4), 805. doi: 10.1111/j.1365-3059.2009.02068.x
Coyne, D., Williamson, V., Tchabi, A., Baimey, H., Rotifa, I., 2012. Comparison of pathogenicity of geographically separate populations of Scutellonema bradys on yam (Dioscorea spp.) in West Africa. Nematropica, 42(2), 181-190. http://journals.fcla.edu/nematropica/article/view/81848/78971
Decker H; Casamayor GR; Bosch D, 1967. Observaciones sobre la presencia del nemátoda Scutellonema bradys en al tuberculo de ±ame en la provincia de Oriente (Cuba). CENTRO, Boletin de Ciencias Technologfa de la Universidad Central de Las Villas, 2:67-70.
EPPO, 2014. PQR database. Paris, France: European and Mediterranean Plant Protection Organization. http://www.eppo.int/DATABASES/pqr/pqr.htm
Goodey T, 1935. Observations on a nematode disease of yams. Journal of Helminthology, 13:173-190.
Humphreys-Pereira DA; Williamson VM; Lee S; Coyne DL; Salazar L; Gómez-Alpízar L, 2014. Molecular and morphological characterisation of Scutellonema bradys from yam in Costa Rica and development of specific primers for its detection. Nematology, 16(2):137-147. http://booksandjournals.brillonline.com/content/journals/10.1163/15685411-00002752
International Institute of Tropical Agriculture, 1984. A system to increase seed yam production. Research Highlights for 1983. Ibadan, Nigeria: IITA, 103-107.
Jatala P; Bridge J, 1990. Nematode parasites of root and tuber crops. In: Luc M, Sikora RA, Bridge J, eds. Plant Parasitic Nematodes in Subtropical and Tropical Agriculture. Wallingford, UK: CAB International, 137-180.
Kermarrec A; Castagnone-Sereno P; Degras L; Anais A; Denon D, 1987. Nouvelle distribution Scutellonema bradys (Tylenchida: Hopolaiminae) dans le Caraibe. Le cas des Antilles Francaises. Mdedlingen van de Faculteit Landbouwwetenschappen Rijksuniversiteit Gent, 52:617-624.
Lordello AIL; Monteiro AR; Lordello RRA, 2005. Occurrence of dry rot of yams at São Paulo State, in Brazil. (Ocorrência do nematóide da casca preta em inhame no Estado de São Paulo.) Revista de Agricultura (Piracicaba), 80(3):356-357.
Lordello LGE, 1959. A nematosis of yam in Pernabuco, Brazil, caused by a new species of the genus Scutellonema. Revista Brasileira de Biologia, 19:33-41.
Merny G; Fortuner R, 1973. Survey on the plant parasitic nematodes associated with various crops in the Republic of the Gambia. Report of Office de la Recherche Scientifique et Technique Outre-Mer (ORSTOM), Laboratoire de Nematologie, Centre de Dakar (Sénégal).
Nadakal AM; Thomas N, 1967. Observations of nematodes associated with dry rot of Dioscorea alata L. Science and Culture, 33:142-143.
Olabiyi, T. I., Ogunbowale, B. B., 2010. Pathogenicity Study of Meloidogyne incognita and Scutellonema bradys on White Yam Cultivars in Nigeria. World Journal of Fungal and Plant Biology, 1(1), 10-14. http://idosi.org/wjfpb/wjfpb1(1)10/3.pdf
Park SD; Khan Z; Kim SeJong; Kim KiJae; Min KiKun, 1998. Occurrence and distribution of plant parasitic nematodes in yam (Dioscorea batatas) fields in Korea. International Journal of Nematology, 8(2):141-144; 12 ref.
Sadik S; Okereke OU, 1975. A new approach to improvement of yam, Dioscorea rotundata. Nature, 254:134-135.
Sher SA, 1964. Revision of the Hoplolaiminae (Nematoda). III. Scutellonema Andrássy, 1958. Nematologica, 9:421-433.
Smit JJ, 1967. Nematodes. In: Coursey DG, ed. Yams. London, UK: Longmans, 115-120.
Unny KL; Jerath ML, 1965. Parasitic nematodes on Dioscorea spp. in eastern Nigeria. Plant Disease Reporter, 49:875-876.
Wood TG; Smith RW; Johnson RA; Komolafe PO, 1980. Termite damage and crop loss studies in Nigeria - pre-harvest losses to yams due to termites and other soil pests. Tropical Pest Management, 26(4):355-370
Baimey H, Coyne D, Labuschagne N, 2006. Effect of fertiliser application on yam nematode (Scutellonema bradys) multiplication and consequent damage to yam (Dioscorea spp.) under field and storage conditions in Benin. International Journal of Pest Management. 52 (1), 63-70. DOI:10.1080/09670870600552380
Baimey H, Coyne D, Labuschagne N, 2009. Pathogenicity of Scutellonema bradys populations from different geographical areas in Benin on yam (Dioscorea spp.). Crop Protection. 28 (9), 715-721. http://www.sciencedirect.com/science/journal/02612194 DOI:10.1016/j.cropro.2009.05.009
Baudin P, 1956. (Les maladies parasitaire des ignames en Côte d'Ivoire). In: Revue de Mycologie, 21 (2) Paris, 87-111.
Belliard A, Kermarrec A, 1978. The yam nematode (Scutellonema bradys) from the tubers of Dioscorea trifida in the Dominican Republic. (Presence du nematode de l'igname (Scutellonema bradys) dans les tubercules de Dioscorea trifida en Republique Dominicaine.). Nouvelles Agronomiques des Antilles et de la Guyane. 4 (1), 49-51.
Berg E van den, Tiedt L R, Coyne D L, Ploeg A T, Navas-Cortés J A, Roberts P A, Yeates G W, Subbotin S A, 2013. Morphological and molecular characterisation and diagnostics of some species of Scutellonema Andrássy, 1958 (Tylenchida: Hoplolaimidae) with a molecular phylogeny of the genus. Nematology. 15 (6), 719-745. http://booksandjournals.brillonline.com/content/10.1163/15685411-00002714
Bridge J, 1972. Nematode problems with yams (Dioscorea spp). In: PANS, 1 89-91.
CABI, Undated. Compendium record. Wallingford, UK: CABI
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Cadet P, Daly P, 1996. Use of nematicides to produce yam planting material free of Scutellonema bradys in Martinique (French West Indies). Crop Protection. 15 (2), 187-195. DOI:10.1016/0261-2194(95)00125-5
Coimbra J L, Almeida N S de, Garrido M da S, Soares A C F, Sousa C da S, Carmo D O do, 2006. Plant parasitic nematodes associated with exotic and native fruit trees in the Reconcavo Region of the State of Bahia, Brazil. (Nematóides fitoparasitos associados a fruteiras nativas e exóticas na região do Recôncavo da Bahia, Brasil.). Magistra. 18 (1), 48-51. http://www.magistra.ufba.br/
Coyne D L, Akpheokhai L I, Adeniran A F, 2011. The yam nematode (Scutellonema bradys), a potential threat to potato (Solanum tuberosum) production in West Africa. Plant Pathology. 60 (5), 992-997. DOI:10.1111/j.1365-3059.2011.02459.x
Coyne D L, Kolombia Y A, Kariuki G, Luambano N, Bert W, 2016. First report of dry rot disease of yam caused by Scutellonema bradys in East Africa. Plant Disease. 100 (8), 1794. http://apsjournals.apsnet.org/loi/pdis DOI:10.1094/PDIS-12-15-1524-PDN
Coyne D L, Tchabi A, Baimey H, Labuschagne N, Rotifa I, 2006. Distribution and prevalence of nematodes (Scutellonema bradys and Meloidogyne spp.) on marketed yam (Dioscorea spp.) in West Africa. Field Crops Research. 96 (1), 142-150. DOI:10.1016/j.fcr.2005.06.004
Coyne D, Claudius-Cole A, 2009. Scutellonema bradys, the yam nematode, newly reported affecting Irish potato (Solanum tuberosum) in Nigeria. Plant Pathology. 58 (4), 805. DOI:10.1111/j.1365-3059.2009.02068.x
Coyne D, Williamson V, Tchabi A, Baimey H, Rotifa I, 2012. Comparison of pathogenicity of geographically separate populations of Scutellonema bradys on yam (Dioscorea spp.) in West Africa. Nematropica. 42 (2), 181-190. http://journals.fcla.edu/nematropica/article/view/81848/78971
DECKER H, CASAMAYOR GARCÍA R, BOSCH D, 1967. [English title not available]. (Observaciones sobre la presencia del nemátodo Scutellonema bradys en el tubérculo del ñame, en la provincia de Oriente (Cuba).). Bol. Cienes Tecnol. Univ. cent. 2 (3), 67-70.
Humphreys-Pereira D A, Williamson V M, Lee S, Coyne D L, Salazar L, Gómez-Alpízar L, 2014. Molecular and morphological characterisation of Scutellonema bradys from yam in Costa Rica and development of specific primers for its detection. Nematology. 16 (2), 137-147. http://booksandjournals.brillonline.com/content/journals/10.1163/15685411-00002752 DOI:10.1163/15685411-00002752
Kermarrec A, Castagnone-Sereno P, Degras L, Anais A, Denon D, 1987. (Nouvelle distribution Scutellonema bradys (Tylenchida: Hopolaiminae) dans le Caraibe. Le cas des Antilles Francaises). In: Mdedlingen van de Faculteit Landbouwwetenschappen Rijksuniversiteit Gent, 52 617-624.
Kwoseh C K, Plowright R A, Bridge J, Asiedu R, 2005. Yam-based Farm Practices and Nematode Problems in Stored Yams (Dioscorea spp.) in Ghana. Journal of Science and Technology. 25 (2), 35-43. DOI:10.4314/just.v25i2.32943
Lordello A I L, Monteiro A R, Lordello R R A, 2005. Occurrence of dry rot of yams at São Paulo State, in Brazil. (Ocorrência do nematóide da casca preta em inhame no Estado de São Paulo.). Revista de Agricultura (Piracicaba). 80 (3), 356-357.
Merny G, Fortuner R, 1973. Survey on the plant parasitic nematodes associated with various crops in the Republic of the Gambia. In: Report of Office de la Recherche Scientifique et Technique Outre-Mer (ORSTOM), Sénégal: Laboratoire de Nematologie, Centre de Dakar.
Muniz M de F S, Silva E J da, Cunha e Castro J M da, Rocha F da S, Alencar L M C de, Gonzaga V, 2012. Intensity of dry rot disease of yam in the state of Alagoas, Brazil. Nematropica. 42 (2), 198-200. http://journals.fcla.edu/nematropica/article/view/81850/78973
Olabiyi T I, Ogunbowale B B, 2010. Pathogenicity Study of Meloidogyne incognita and Scutellonema bradys on White Yam Cultivars in Nigeria. World Journal of Fungal and Plant Biology. 1 (1), 10-14. http://idosi.org/wjfpb/wjfpb1(1)10/3.pdf
Samuel A T, Violet N O, Dee S A, 2014. Morphological characteristics and incidence of diseases on white yam (Dioscorea rotundata L. Poir) tubers in Abuja, Nigeria. Nature and Science. 12 (7), 58-65. http://www.sciencepub.net/nature/ns1207/010_25308ns120714_58_65.pdf
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