Avena sterilis (Sterile Oat)

Scientific name

Avena sterilis  L.

Synonyms

Avena affinis Bernh. ex Steud.; Avena algeriensis Trab.; Avena byzantina var. solida (Hausskn.) Maire & Weiller; Avena fatua var. ludoviciana (Durieu) Fiori; Avena X ludoviciana Durieu; Avena ludoviciana Durieu; Avena ludoviciana var. ludoviciana Durieu; Avena macrocalyx Sennen; Avena macrocarpa Moench; Avena melillensis Sennen & Mauricio; Avena nutans St.-Lag.; Avena persica Steud.; Avena sativa var. ludoviciana (Durieu) Fiori; Avena sativa var. sterilis (L.) Fiori; Avena sativa ssp. sterilis (L.) de Wet; Avena sensitiva hort. ex Vilm.; Avena solida (Hausskn.) Herter; Avena sterilis var. algeriensis (Trab.) Trab.; Avena sterilis ssp. ludoviciana (Durieu) Nyman; Avena sterilis var. ludoviciana (Durieu) Husn.; Avena sterilis ssp. macrocarpa (Moench) Briq.; Avena sterilis var. solida (Hausskn.) Malzev; Avena turonensis Tourlet

Common names

Animated oat

Family

Poaceae  (Gramineae)

Origin

Native to the Mediterranean.

Naturalised distribution (global)

Avena sterilis 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 sterilis has been recorded in wheat growing areas in the three East African countries (Terry and Michieka, 1987).

Habitat

In Kenya, Avena sterilis is a roadside weed or weed of arable land among grain crops up to 2600 m altitude. Elsewhere, in warm-temperate regions in deep, fertile soils to sandy soils, flooded paddy fields, rocky hillsides up to 2000 m elevation; it is a weed of cereal fields, olive groves, vineyards and waste land.

Description

Avena sterilis is an annual grass, up to 180 cm tall.

The leaf blades grow to 45 cm long and 4-18 mm wide with ligules up to 6 mm long.

The panicle (flower cluster) is loose up to 30 cm long and 20 cm wide. Spikelets (unit of a flower cluster) are 35-50 mm long, the narrowly lance-shaped (lanceolate) glumes (small leaf-like structures below or enclosing a flower, or a flower spikelet in the grasses and sedges) enclosing the 2-5 florets with the articulation only below the lowest one of these. Dorsal awns (bristle-like structures) are 5-8 cm long, the upper 2 florets are hairless (glabrous) and awnless, inner glume with brown hairs.

Lemmas (lower and outermost of the two scales that are part of a grass floret and enclose a grass seed) are 25-40 mm long, hairy with an elbowed awn 4-9 cm long.

The grains are highly viable.

Reproduction and dispersal

Avena sterilis are primarily transported by man and grazing animals. It is mainly transported by man and grazing animals. The seeds are transported as a contaminant in harvested cereals.

Similar species

Plants in the genus Avena resemble other oats and wheat (Triticum spp.) when growing, only differing from wheat by the fact that upon maturity its ears hang downwards, while wheat ears mature facing up.

  • Avena sterilis can be distinguished from others in the genus Avena as follows; the minute hairs on the back of the lowest palea (the upper and innermost of the two scales that are part of a grass floret and enclose a grass seed).
  • Its floret (grass flower) is generally longer and wider than that of Avena fatua.
  • In Avena sativa the 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;
  • In 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;
  • In Avena sativa: lemmas smooth and shiny, whereas those of Avena sterilis and Avena fatua are grainy or rough.

Environmental and other impacts

Avena sterilis is a palatable grass but its benefits are outweighed by its negative impacts. A. sterilis invades and lowers the quality of a field crop, competes for resources with the crops and contaminates cereal grains and seeds. It has been identified as one of the most serious threats to wheat and barley production in East Africa (CABI Crop Compendium 2011).

A. sterilis is on the USA Federal Noxious Weeds List.

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 sterilis 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. sterilis through an integrated approach involving such practices such as crop rotation, increased crop sowing rate and hand-weeding.

When it is a weed of cereal crops such as wheat, oats, barley it is difficult to distinguish A. sterilis from the crop until flowering. Therefore, A. sterilis should only be removed after flowering. Because A. sterilis seeds can stay dormant in the soil up to five years, it is important to remove plants before they produce seedA. sterilis seeds should be removed before milling to ensure good grain quality. Some herbicides can be effective but 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. sterilis infestations.

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

Legislation

In Kenya Avena sterilis 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).

Its common name, 'animated oat' refers to the fact that this oat has spikelets that twist or move when exposed to sudden moisture, due to the hygroscopic action of the awns.

References

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 sterilis." Wikipedia, The Free Encyclopedia www.wikipedia.org/ wiki/Avena_sterilis. Accessed January 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