Bearded Oat

Avena barbata Pott ex Link

Family: Poaceae.

Names:

Bearded Oat

Summary:

A robust, tufted, annual grass with hollow stems growing to over 1 m tall. It has an open seed head with large brown seeds hanging from delicate branches. The spikelets are 2-2.5 cm long with 2 or 3 florets. The outer segment of each floret (lemma) has a prominent bent and twisted awn. The hairs on the lemma are white and at right angles to the lemma. The seeds are usually dark brown but may be dark yellow. Native to the Mediterranean region, it is a widespread weed of disturbed bushland and roadsides and flowers in spring.

Description:

Cotyledons:

One.

Leaves:

Emerging leaf rolled in the bud.
Blade - Flat. 100-300 x 3-6 mm. Usually hairless but immature leaves and stems may have hairs. Rough to touch. Anticlockwise twist. Rolled in the bud.
Ligule - Membranous.
Auricles - None.
Sheath - Overlapping.
Collar - Often a lighter colour.

Stems:

Erect. Up to 1.7 m. Several from base. Tufted. More or less hairless. Hollow with solid nodes.

Flower head:

Drooped to one side. 200-350 mm long. Toward ends of stems on slender pendulous branches carrying 1-2 seeds each.

Flowers:

On one side of stem. 18-30 mm. Loose.
Spikelets - drooping on fine stalks. Gaping.
Florets - 2-3
Glumes - Broadly spear shaped, pale with green veins and unequal length of 20-25 mm.
Lemma - Shorter than glumes, awned, covered in pale, white and silky hairs and two short bristles at the tip. Hairs on the lemma tend to be more erect than in other species.
Awns - More than twice as long as their lemmas, bent like a knee.
Stamens -
Anthers -

Seeds:

Gold or brown. Oval to cylindrical, 10-20 mm long excluding the awn by 2-4 mm diameter. Surface grooved and with long pale hairs. Two bristles at tip. Awn about 30 mm long and bent.

Roots:

Fibrous

Key Characters:

Lemmas with silky hairs.
Twisted awns.
Seed head droops to one side.
Membranous ligule.
No auricles.
Emerging leaf rolled in the bud.
Sheath rolled and overlapping.

Biology:

Life cycle:

Annual. Germinates autumn/winter and usually flowers from August to December.

Reproduction:

Flowering times:

Any time of year, but most common from September to January.

Seed Biology and Germination:

Hard seeded.
Most of the germinable seed emerges soon after the break of the season.

Vegetative Propagules:

None

Allelopathy:

Stubble is allelopathic.

Population Dynamics and Dispersal:

Spread by seed.

Origin and History:

Mediterranean.

Distribution:

ACT, NSW, SA, VIC, WA.
Occurs mainly on roadsides.

Courtesy Australia's Virtual Herbarium.

Habitats:

Roadsides, cultivated crops and disturbed areas.

Climate:

Temperate

Soil:

Found on most soil types, but prefers the heavy grey clays and in particular the self mulching soils.

Plant Associations:

Grasslands, woodlands and cotton bush country.

Significance:

Beneficial:

Fodder

Detrimental:

Weed of crops causing yield reductions due to competition, however it is seldom the major species of wild oat in cropping systems and more commonly tends to be predominant on roadsides.
Contaminates grain.
Weed of wastelands and roadsides.
Carries diseases such as rusts of cultivated oats.

Toxicity:

Not reported to be toxic in Australia.

Legislation:

None.

Management and Control:

Most Wild Oat infestations occur because of our activities rather than natural spread. Plant clean seed. Clean tillage, harvesting machinery, vehicles and radiator grills when entering clean areas. Cover trucks transporting grain. Feed clean hay and grain to stock.

Thresholds:

1 plant/m2 is sufficient to contaminate grain.
10-20 plants/m2 causes around 10% yield loss in cereals.

Eradication strategies:

Eradication will be difficult because of a very small number of very dormant seeds, however reductions of populations to low levels should be achievable.
Strategies that target the control of seed set can reduce populations fairly quickly. Completely stopping seed set for 2 years is expected to severely reduce the population.
Increase cereal densities to more than 75 plants/m2.
Aim to;
1) increase germination and emergence with shallow early cultivations
2) decrease survivorship with herbicides, increased crop density and good crop agronomy.
3) reduce fecundity with herbicides and good crop agronomy.
4) reduce seed rain by seed catching.
5) reduce seed carryover by burning.

In non agricultural situations
Prevent seed set for at least 3-5 years. This may be achieved by manual removal, regular mowing, grazing or spraying. Pay particular attention in spring when plants may produce seeds quickly.
Grass-selective herbicides are preferred for control in most situations. A mixture of 5 mL quizalofop(100g/L) or 8 mL Fusilade®Forte or 1 mL Verdict®520 plus 100 mL spray oil in 10 L water applied in winter before flowering will provide control of many grasses with little damage to broad-leaved species. In situations where control of all annual species is required use 40 mL glyphosate(450g/L) in 10 L water as a hand spray and spray until just wet any time the plant is actively growing before seed set, or use 2 L/ha glyphosate(450g/L) as an overall spray. For selective control of annual grass species apply 500 mL/ha quizalofop(100g/L) or 800 mL/ha Fusilade®Forte or 100 mL/ha Verdict®520 plus 1% spray oil when the plants are actively growing prior to flowering. Repeat as required.

Herbicide resistance:

None reported.

Biological Control:

Unlikely because it is closely related to Oats.

Related plants:

Bearded Oat (Avena barbata) occurs mainly on roadsides and non agricultural land. The lemma has 2 fine 3-12 mm long bristles that extend beyond the bend in the awn and the spikelets droop to one side.
Ludo Wild Oat (Avena sterilis ssp. ludoviciana) has a larger seed with low lying hairs and the tail of the seed is not spread. The spikelets do not break up easily like other wild oats and the secondary seeds don't have an abscission scar. It is more prevalent in the northern grain belt of the eastern states but is also common at low levels in the southern grain belt. 85% of Wild Oat infestations in Victoria contained both Avena fatua and Avena ludoviciana. Ludo Wild Oat flowers and shatters about a week earlier than Wild Oat.
Oats (Avena sativa) is awnless or has awns that are not twisted and has plump golden seed.
Sand Oat (Avena strigosa) has black seed. Saia is a commonly grown cultivar.
Sterile Oat (Avena sterilis) tends to occur on roadsides.
Wild Oat (Avena fatua) has larger, darker seeds and the hairs on the lemma tend to lay flatter and the bend in the seed awn occurs beyond the tail of the seed rather than below it. The tail of the seed is not spread and it tends to be found on agricultural land. It is more common in southern cropping systems. All seeds shed individually rather than in groups of 2-3. Wild Oat flowers and shatters about a week later than Ludo Wild Oat.

Plants of similar appearance:

Wild oats can be distinguished from wheat and barley in the vegetative phase because the leaf twists in the opposite direction, they have no auricles and the ligule is much larger.
Annual ryegrass, Barley grass, Brome grass, Darnel, Fountain grass, Guildford grass, Quaking grass, Sand fescue, Silver grass, Volunteer cereals, Wild oats, Toad rush, Winter grass are sometimes confused with Bearded Oat when young.

References:

Black, J.M. (1965). Flora of South Australia. (Government Printer, Adelaide, South Australia). P165. Seed diagram.

Burbidge, N.T. and Gray, M. (1970). Flora of the Australian Capital Territory. (Australian National University Press, Canberra). P38. Seed diagram.

Ciba Geigy 2.

Cunningham, G.M., Mulham, W.E., Milthorpe, P.L. and Leigh, J.H. (1992). Plants of Western New South Wales. (Inkata Press, Melbourne). P62-63. diagram.

Gilbey, D. (1989). Identification of weeds in cereal and legume crops. Bulletin 4107. (Western Australian Department of Agriculture , Perth). P59. Diagram.

Lamp, C. and Collet, F. (1990). A Field Guide to Weeds in Australia. (Inkata Press, Melbourne).

Lazarides, M. and Hince, B. (1993). CSIRO handbook of economic plants of Australia. (CSIRO, Melbourne). #150.1.

Marchant, N.G., Wheeler, J.R., Rye, B.L., Bennett, E.M., Lander, N.S. and Macfarlane, T.D. (1987). Flora of the Perth Region. (Western Australian Herbarium, Department of Agriculture, Western Australia). p941.

Paterson, J.G. (1977). Grasses in South Western Australia. (Western Australian Department of Agriculture Bulletin 4007). P27-28. Diagram.

Wilding, J.L. et al. (1987). Crop weeds. (Inkata Press, Melbourne). p18. Photos. Diagram.

Acknowledgments:

Collated by HerbiGuide. Phone 08 98444064 or www.herbiguide.com.au for more information.