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Pest Description
IDENTITY: Scientific name: Subanguina wevelli
(Van den Berg, 1985) Ebsary, 1991
Comon name: A seed-gall nematode

NOTES ON TAXONOMY AND BIOLOGY:  This species, which was described as Afrina wevelli,  is characterized by a large and irregularly shaped basal bulb, a well defined post-uterine sac that extends for less than 50% of the distance between vulva and anus and a lateral field that consists of a wide band marked by up to 10 or more faint longitudinal inner lines.  Afrina wevelli was considered a junior synonym of A. agrostis (Steinbuch, 1799) Filipjev 1939 (Chizhov and Subbotin, 1990). This taxonomic action had serious regulatory impact on A. wevelli because of the synonymy of A. funesta (vector of the lethal yellow slime bacterium) with A. agrostis (Stynes and Bird, 1980). The synonym of A. wevelli with A.  agrostis was rejected by Ebsary (1991) who placed this species in the genus Subanguina. However, in spite of these morphological affinities, these three species can be differentiated by molecular techniques (Powers et. al. 2001; Riley et. al., 1988). A. wevelli second-stage juveniles (J2) emerge from the seed galls in the soil and crawl onto the newly germinated weeping love grass seedlings. J2 become located between young leaves and penetrate flower buds during flower bud formation. J2, J3, and J4 stimulate the formation of galls instead of seeds. Juvenile development is completed in the galls. Newly formed females deposit eggs, which hatch and produce J2, which remain encased into the galls and perpetuate the plant infection in the following years. Dried galls are harvested with seeds.

GEOGRAPHICAL DISTRIBUTION:  This nematode has been reported only in South Africa.

HOSTS: The principal host of S. wevelli is weeping love grass (Eragrostis curvula).

CROP LOSSES: The direct damage caused by this nematode has not been assessed. However, serious regulatory implications for the grain export to national and international markets can be caused by the accidental introduction of this species due to its morphological similarities with Anguina funesta, a prohibited pest by many countries.

MEANS OF MOVEMENT AND DISPERSAL: Through the characteristic dark seed galls harboring the nematode juveniles in harvested grains.

RATING: (L) In spite of its limited economic importance, S.  wevelli, due to its morphological and taxonomic proximity with Anguina funesta, has had regulatory significance in the past. But regulations should be clarified based on the fact that molecular identification techniques are now available.  The direct economic risk posed by this nematode to the US is rated as very low.

    Powers, T.O., A. L. Szalanski, P. G. Mullin, T. S. Harris, T. Bertozzi, and J. A. Griesbach. 2001. Identification of seed gall nematodes of agronomic and regulatory concern with PCR-RFLP of ITS1. Journal of Nematology 33:191-194.
    Price, P. C., J. M. Fisher, and A. Kerr. 1979. On Anguina funesta n. sp. and its association with Corynebacterium sp. in infecting Lolium rigidum. Nematologica 25; 76-85.
    Riley, I.T., T. B. Reardon, and A. C. McKay. 1988. Electrophoresis resolution of species boundries in seed-gall nematodes, Anguina spp. (Nematoda: Anguinidae), from some graminaceous hosts in Australia and New Zealand. Nematologica 34:401-411.
    Stynes, B. A., and A. F. Bird. 1980. Anguina agrostis, the vector of annual ryegrass toxicity in Australia. Nematologica 26:475-490.
    Van Den Berg, E. 1985. Notes on the genus Afrina Brzeski, 1981 (Anguinidae: Nematoda) with description of new and known species. Phytophylactica 17:69-79.