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As flowering specimens are very leafy and with a similar habit to many free-living plants, people who are not familiar with root hemi-parasites are unlikely to recognize that A. vogelii is indeed parasitic. Below ground, bright orange stems are attached to host roots by a spherical haustorium up to 2 cm in diameter. This is composed of a mass of host and parasite tissue and the orange adventitious roots of the parasite. Plants grow to 30-45 cm tall, often as a single stem but sometimes branching from near soil level. The stems and leaves, which can be 1.5 to 3.5 cm long by 0.3 to 1.5 cm wide, are conspicuously hairy. Leaf shape, particularly the nature and extent of toothing along the edge of the lamina, varies considerably. In parts of West Africa, leaf margins are almost entire, in central and southern Africa they may have two to five widely spaced teeth along each edge while in Kenya plants with five or six sharp teeth, each up to 3 mm long, have been collected. Flowers appear singly on a short stem in the axils of upper leaves or bracts. Up to 10 flowers may open on one day. The flower buds are enclosed in a densely hairy calyx whose five lobes each have a triangular tip with an obtuse apex. The tubular corolla is formed of five petals fused towards the base, so that the flower is bell-shaped when open. The corolla is 0.6 to 1 cm in diameter and somewhat longer than the calyx. The petals are pale yellow and may or may not have three deep red veins. Both types of flowers can be found in a group of plants. The anthers and filaments are glabrous. The flowers wither and remain covering the developing globose seed capsule which swells to approximately 5 mm in diameter at maturity. The dust-like seeds have a complex structure. An outer cell layer of the testa is modified into a cone or a 'trumpet-like' structure about 1 mm long within which the 'kernel' of the seed, measuring about 0.15 mm by 0.25 mm, is suspended. The surface of the seed coat is covered in indentations.

Related invasive species

  • Alectra vogelii

Related Farm Practice

  • People
  • Soil
  • Hosts

Related location

  • Kenya
Impact

A. vogelii is an annual parasitic weed of legume crops, particularly cowpea and groundnut, in semi-arid areas of East, West, Central and Southern Africa. It is closely associated with cultivation, is occasionally found associated with weeds of fallows but rarely in natural vegetation. Copious seed production and a long-lived seed-bank allow the rapid build up of infestations when susceptible crop cultivars are planted. Tiny seeds are easily spread by wind, surface water flow or in crop seed. The genus Alectra is on the USDA Federal Noxious Weed list. Despite the similar life cycle to Striga species which are listed, and potential for crop damage, A. vogelii does not appear on Noxious weed lists in Australia. An assessment of its global invasive potential is given by Mohamed et al. (2006).

Has Cabi datasheet ID
4234
Hosts


Cowpea is the major crop host of A. vogelii throughout its range (Parker and Riches, 1993). Bambara, groundnuts, common bean, soyabean, mung bean, and tepary are also common hosts and there have been occasional reports of infestation of chickpea and runner bean. Pigeon pea is the only widely grown grain legume which is not parasitized. Although A. vogelii can attack the crops listed there is clear geographic variation in the host range in different regions of Africa. Host range tests (Riches et al., 1992), indicate that populations from Mali, Nigeria and Cameroon can attack groundnut and cowpea. Samples from eastern Botswana and northern areas of Northern Province, South Africa attack mung bean in addition to cowpea and groundnut. Populations sampled from Kenya, Malawi and eastern areas of Northern Province, South Africa, parasitize bambara as well as crops which are susceptible elsewhere. No association has been observed between morphological variation, largely in leaf shape, and host preference. Many other legumes are hosts including species such as lab lab and velvet bean which are often introduced as fodder or green manure crops in infested areas. A. vogelii has a wide host range and has been occasionally recorded as parasitic on non-legume weeds including Acanthospermum hispidum and Vernonia poskeana (Compositae), Euphorbia (Euphorbiaceae) and Hibiscus (Malvaceae) species in addition to common legume weeds including Indigofera and Tephrosia species.

Oss tagged
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