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NOTES ON TAXONOMY AND BIOLOGY: Aphelenchoides arachidis female are characterized by a lateral field marked by two incisures, a stylet 11-12 µm long with distinct knobs, a postvulval uterine sac extending for half the vulva-anus distance, and a sub-cylindroid tail with a bluntly rounded terminus provided by a mucro. The nematode develops and reproduces in the seed coat (testa), and also in the pod, root and hypocotyl tissues causing discoloration, necrosis and brown stripes within the testas. The nematode-infected seeds appear shrunken and dark. This pest can survive in low numbers in pods and seeds (Bridge and Hunt, 1985).
GEOGRAPHICAL DISTRIBUTION: This nematode has been reported only in Nigeria.
HOSTS: Peanut (Arachis hypogaea) is the principal host; other agronomic crops and weeds can be infected without showing any symptoms or damage. These hosts include corn (Zea mays), rice (Oryza sativa), sugrcane (Saccharum offcinarum) and unidentified grasses.
CROP LOSSES: Nematode infection does not suppress yield, but causes serious qualitative damage and predisposes seeds to fungal infection by Fusarium sp., Macrophomina phaseolina, Rhyzoctonia solani and Sclerotium rolfsii. These infected seeds are undergraded and unmarketable (Bridge and Hunt, 1985; Minton and Baujard, 1990, Stokes, 1980).
MEANS OF MOVEMENT AND DISPERSAL: Aphelenchoides arachidis is disseminated by infected peanut hulls and seeds.
RATING: (L) Because of its limited distribution (Nigeria), Aphelenchoides arachidis has not caused major economic losses, but this pest can become a major economic pest if introduced in large peanut-producing areas (Minton and Baujard, 1990). The chances of introduction of this nematode into the United States are limited because imported peanut seeds are used for food processing. Plant breeders should be extremely cautious in importing peanut seeds from Nigeria.
REFERENCES:
Bridge, J., and D. J. Hunt. 1985. Aphelenchoides
arachidis. CIH description of plant parasitic nematodes Set 8, No.
116, pp. 3. St. Albans, UK: Commonwealth Institute of Helminthology.
CAB International. 2001. Aphelenchoides arachidis
in: Crop protection compendium, global module, 3rd edition. Wallingford,
UK: CAB International.
Minton, N. A., and P. Baujard. 1990. Nematode parasites
of peanuts. Pp. 285-320 in M. Luc, R. A. Sikora, and J. Bridge eds. Plant
parasitic nematodes in tropical and subtropical agriculture. Wallingford,
UK: CAB International.
Stokes, D. E. 1980. The effects of the testa nematode,
Aphelenchoides
arachidis, on peanuts. Nematology Circular No. 68, Florida Department
of Agriculture and Consumers Services, Division of Plant Industry, Gainesville,
FL, USA.