Avena fatua (Common Wild Oat)

Scientific name

Avena fatuaL.

Synonyms

Anelytrum avenaceum Hack.; Avena fatua var. glabrata Peterm.; Avena fatua var. intermedia Hartman; Avena fatua var. intermedia Husn.; Avena fatua var. intermedia Vasc.; Avena fatua ssp. meridionalis Malzev; Avena fatua var. vilis (Wallr.) Hausskn.; Avena fatua var. vilis (Wallr.) Malzev; Avena intermedia Lindgr.; Avena intermedia T. Lestib.; Avena lanuginosa Gilib.; Avena meridionalis (Malzev) Roshev.; Avena patens St.-Lag.; Avena pilosa Scop.; Avena sativa var. fatua (L.) Fiori; Avena sativa var. sericea Hook. f.; Avena septentrionalis Malzev; Avena vilisWallr.

Common names

Common wild oat, wild oat

Family

Poaceae (Gramineae)

Origin

Native to the Mediterranean. Ethiopia, N. Africa, Europe and Asia among other locations

Naturalised distribution (global)

Avena fatua is naturalised in many parts of the world where cereals are grown in Africa, Europe and Asia among other locations.

Introduced, naturalised or invasive in East Africa

Avena fatua is found in the highlands of the three East African countries (Terry and Michieka, 1987) and in Kenya has been recorded in wheat growing areas in Rift Valley and Central provinces.

Habitat

Avena fatua is a roadside weed or weed of arable land among grain crops at altitudes of between 2100-2730 m.

Description

Avena fatua is an erect, tufted or ascending stout annual grass 30-150 cm tall that is a typical oat in appearance, a green grass with hollow, erect stems to 150 cm. It is sparsely hairy.

Leaf blades are flat, about 10-45 cm long and 3-15 mm wide with the membranous small structure at the junction of the leaf sheath and leaf blade (ligules) up to 6 mm long. The long dark green leaves are rough due to small hairs. The youngest leaf is rolled up.

The ligule is often irregularly toothed (dentate, fringed). The leaf bases do not have ear-like projections (auricles). Leaf sheaths are smooth or slightly hairy, especially in younger plants.

The inflorescence of Avena fatua is a loose, open panicle with 2-3-flowered stalked (pedicelled) spikelets. The panicle is 10-40 cm long and up to 20 cm wide with spreading branches and the spikelets hanging from long stalks (pedicels). Each of the 2-3 florets has an oval abscission scar at its base, causing them to fall separately.

Spikelets are 18-28 mm long, with the narrow lance-shaped (lanceolate) glumes enclosing the 2-3 florets each of these with an articulation below glumes.

Lemmas are hairy, 14-20 mm long. Seed has an awn 2.5-4 cm long. Grains are 6-8 mm long. Seeds of A. fatua are viable for 3-8 years.

Reproduction and dispersal

Avena fatua is spread as a contaminant of cereal seed, by people, by farm animals and through contaminated shared farm implements. The seedlings are also hairy. The awn of the A. fatua seed twists into a helix on drying and untwists when wet, thereby drilling the seed into the soil.

Similar species

Plants in the genus Avena resemble wheat (Triticum spp.) when growing; only obviously differing from wheat upon maturity when its ears hang downwards, while mature wheat ears face upwards.

  • In vigour, growth habit and large spikelets, Avena fatua is similar in appearance to
    cultivated oat (Avena sativa). However, Avena sativa has a denser panicle (flower cluster), the spikelets (unit of a flower cluster) have only 0-1 awn (bristle-like structure), and the florets (grass flower) do not readily separate and shed.
  • Avena sativa the crop is further distinguished from A. fatua by spikelets which in the crop are not articulated above the glumes (small leaf-like structures below or enclosing a flower, or a flower spikelet in the grasses and sedges) and the lemmas (lower and outermost of the two scales that are part of a grass floret and enclose a grass seed) are smooth.
  • Avena sativa: basal scar is horizontal rather than oblique as in A. sterilis and A. fatua and its rachis (main stem of flower cluster) tip is jagged, pointed, and fractured;
  • Avena sativa: scutellum (modified seed leaf) outline on the one-seeded fruit of a grass (caryopsis) is clearly evident, whereas it is not very clear on A. sterilis and usually less so on A. fatua;
  • Avena sativa: Lemmas smooth and shiny, whereas those of A. sterilis and A. fatua are grainy or rough.

Economic and other uses

Avena fatua is palatable and has medicinal uses but its benefits are outweighed by its negative impacts.

Environmental and other impacts

Avena fatua is considered to be one of the world's worst agricultural weeds and it is increasing in importance (CABI Crop Compendium 2011). It is an especially serious weed in grain crops such as barley and wheat. A  fatua invades and lowers the quality of a field crop, typically wheat or oat fields and competes for resources with the crops. It causes soil dryness and provides favourable conditions for diseases and pests (e.g. frit fly, nematodes and smut).

Management

The precise management measures adopted for any plant invasion will depend upon factors such as the terrain, the cost and availability of labour, the severity of the infestation and the presence of other invasive species. Some components of an integrated management approach are introduced below.

The best form of invasive species management is prevention. As Avena fatua is so widespread this is unlikely to be possible in many instances. If prevention is no longer possible, it is best to treat the weed infestations when they are small to prevent them from establishing (early detection and rapid response). Controlling the weed before it seeds will reduce future problems. Control is generally best applied to the least infested areas before dense infestations are tackled. Consistent follow-up work is required for sustainable management.

There are effective nonchemical methods for controlling A. fatua through soil cultivation and crop rotation.

When it is a weed of cereal crops such as wheat, oats, barley it is difficult to distinguish A. fatua from the crop until flowering. Therefore, the wild oat should only be removed after flowering. Because A. fatua seeds can stay dormant in the soil up to 10 years, it is important to remove plants before they produce seedA. fatua seeds should be removed before milling to ensure good grain quality. A controlled burn after harvest can reduce the viability of the A. fatua seeds that remain on the soil surface. Many selective herbicides can be effective alone, in mixtures or sequences. Correct timing and rate of herbicide application is critical to maximise control. When using any herbicide always read the label first and follow all instructions and safety requirements. If in doubt consult an expert.

Careful cleaning of sowing material can reduce A. fatua infestations.

The editors could find no information on any biological control agents for this species.

Legislation

In Kenya Avena fatua is declared a noxious weed of Agriculture under the Noxious Weeds Act CAP 325, in Kenya. Accordingly the Minister of Agriculture can compel land owners who have such declared noxious weeds growing on their land to eradicate or have it otherwise removed. However, it is not declared in Uganda and Tanzania.

Notes

Members of the tribe Aveneae (oats) have glumes that are larger than the lemma and that remain on the panicle inflorescence after the grains shatter (persistent glumes). As a specific trait of Avena species, the lemmas end in 2 small teeth and have 2-3 awns arising from the back which are mostly dark-coloured, bent and 3-4 cm long.

References

Bayer Crop Science. Weedspotter - wild oat and winter oat. www.weedfocus.com/content.weedspotter/ 244/1036/e-Tools/e-Tools/Weedspotter.mspx.  Accessed February 2011.

CABI Crop Compendium online data sheet. Avena fatua. CABI Publishing 2011. www.cabi.org/CPC. Accessed March 2011.

Government of Kenya (1983). The Suppression of Noxious Weeds Act: CAP 325 of the Laws of Kenya. 2nd Ed. Government Printer, Nairobi, 5 pp.

Ibrahim, K. M and Kabuye, C.H.S. (1987) An Illustrated manual of Kenya grasses, FAO, Rome.

Terry, P.J. and Michieka, R.W. (1987). Common weeds of East Africa/Maguga ya Africka Masharaiki. FAO, Rome, 184pp.

Wikipedia contributors. "Avena fatua L. " Wikipedia, The Free Encyclopedia en.wikipedia.org/wiki/Avena_fatua. Accessed February 2011.

Editors

Agnes Lusweti, National Museums of Kenya; Emily Wabuyele, National Museums of Kenya, Paul Ssegawa, Makerere University; John Mauremootoo, BioNET-INTERNATIONAL Secretariat - UK.

Acknowledgments

This fact sheet is adapted from The Environmental Weeds of Australia by Sheldon Navie and Steve Adkins, Centre for Biological Information Technology, University of Queensland. We recognise the support from the National Museums of Kenya, Tropical Pesticides Research Institute (TPRI) - Tanzania and Makerere University, Uganda. This activity was undertaken as part of the BioNET-EAFRINET UVIMA Project (Taxonomy for Development in East Africa).

Contact

BioNET-EAFRINET Regional Coordinator: eafrinet@africaonline.co.ke