A tufted, erect, several to many stemmed annual grass to 1.5 m tall. The loosely branched inflorescence has large drooping spikelets that are 2-3 cm long. Each spikelet has 2 or 3 florets. The outer segment of each floret (lemma) has a prominent bent and twisted awn.
The lemma can be hairy or hairless. Sets of 2-3 brown seeds fall intact with the spikelet at maturity. Native to the Mediterranean region and Asia, it is a weed of cropping areas and flowers in spring.
Description:
Cotyledons:
One
Leaves:
Emerging leaf rolled in the bud.
Blade - Flat. Hairless or rough to touch or may have hairs underneath. Up to 18 mm wide. Occasionally with scattered long hairs.
Ligule - Papery and ragged. Obtuse to acute, 0.5-0.8 mm long.
Auricles - none
Sheath - Rolled and overlapping
Stems:
Several arising from the base. Erect. Up to 1700 mm tall. Tufted. Hollow with solid nodes.
Flower head:
Open loose, pyramidal panicle, 100-450 mm long, that is pyramidal in outline with nodding spikelets.
Flowers:
Spikelets - 25-30 mm long. Gaping. Drooping from long thin stalks.
Florets - 2-3. Two lower ones are awned. Remain attached and fall together when ripe.
Glumes - Broadly lance shaped. Tip pointed. 14-35mm long. Hairless.
Palea -
Lemma - Egg shaped, 10-25 mm long. Bottom two thirds clothed in long silky brown hairs. Tip split into 2 papery pointed lobes. 10-25mm long. Becoming hard. Upper 2 have a dark, bent, twisted awn, 15-75mm long. Second lemma strongly attached to flower stalk. Third lemma, if present, is awnless. Lemmas remain attached to each other when shed.
Stamens -
Anthers -
Seeds:
Brown. Narrow oval shaped with a groove one side.
Roots:
Fibrous.
Key Characters:
Sets of 2-3 seeds fall intact at maturity.
Lemma have basal scars when broken off.
Lemma with golden brown hairs.
Twisted awns.
Biology:
Life cycle:
Annual. Flowers in spring. Seeds germinate in autumn. Seedling forms tillers in winter. Stems elongate, flower and set seed in spring. Plant dies in summer, usually with the onset of drought.
Reproduction:
By seed.
Flowering times:
Spring.
Seed Biology and Germination:
Hard seeded.
Tends not to germinate when the temperature exceeds 200C. (Quail and Carter, 1968)
Vegetative Propagules:
None.
Hybrids:
Probably.
Allelopathy:
Probably.
Population Dynamics and Dispersal:
Spread by seed mainly as a contaminant of grain and produce or on machinery.
Mowing and grazing may cause spread of up to 14 m (Auld, 1988).
Most seed falls within 1m of its parent (Thurston and Philipson, 1976).
Birds may spread some seed but those that are eaten don't survive.
Avena sterilis ssp. ludoviciana tends to germinate in several waves from winter to spring somewhat later than Avena fatua (Quail and Carter, 1968).
Seed catching tends to be more effective on Avena sterilis ssp. ludoviciana than Avena fatua because it tends to retain its seed.
Seed production is reduced as cereal crop density increases Radford (1980). With cereal densities above 75 plants/m2 wild oat seed production following treatment with herbicides rarely exceeds 200 seeds/m2 irrespective of the initial density of Wild Oats.
Burning crop stubble destroys some Wild Oat seeds (Nietschke, 1996).
Fertilisers and their placement have had variable results on the effects of WIld Oats on crops. Banding fertiliser generally benefits the crop.
Swathing usually reduces the WIld Oat seed returned to the paddock but may result in extra grain cleaning costs or dockage.
Cultivation
Deep burial prevents seeds germinating but induces dormancy so that if they are brought to the surface in later years they will germinate.
Shallow cultivation encourages germination and recruitment.
Wild Oat seed banks decline more quickly under systems using tyned rather than disc implements for cultivation.
Delayed seeding allows greater control of Wild Oats before planting but in Victorian research Walsh (1995) found it uneconomic and not very effective alone.
Burning
Burning can destroy seed on the soil surface reduce the dormancy of the remaining seed. It is most effective when conducted directly after harvest but in most cases this is not possible (Neitschke, 1996).
Rotations
Continuous cereal and cereal/pulse rotations tend to lead to a build up in Wild Oat numbers. Cereal pasture rotations tend to lead to a reduction in Wild Oat populations.
Origin and History:
Europe and Western Asia.
Distribution:
ACT, NSW, QLD, SA, TAS, VIC, WA.
Tends to be the major species in subtropical cropping systems. Avena fatua tends to predominate in southern areas.
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. Cultivated crop.
Detrimental:
Weed of crops causing yield reductions due to competition. Contaminates grain sample. Weed of disturbed areas 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.
In a survey of northern NSW crops pre emergent herbicides had a mean control level of 70±16% and early post emergent herbicides a control level of 65±18% (Nietschke and Medd, 1996). Overall, tri-allate is best suited to medium to heavy infestations of wild oats and flamprop is best suited to low level infestations.
Flamprop-methyl, flamprop-m-methyl and fenoxaprop-ethyl are the herbicides that provide the best control of seed set when applied at tiller elongation stage and averaged up to 97% reduction in seed set. Applications at booting average around 70% seed set reduction (Nietschke and Medd, 1996).
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.
Cutting crops for silage before Wild Oats sets seed can virtually eliminate Wild Oats in three years (Wilson and Phipps, 1985). Green manuring should be equally effective.
Aim to;
1)increase germination and emergence with shallow early cultivations. Apply some nitrogen before planting to stimulate wild oat germination and make them more susceptible to herbicides.
2)decrease survivorship with herbicides, increased crop density and use good crop agronomy. Delay seeding to allow greater emergence and subsequent control by cultivation or knockdown herbicides before planting.
3)reduce fecundity. Use herbicides and good crop agronomy. Don't use wide row spacings. Plant crop seed as shallow as possible. Band fertilisers. Consider rotations that include silage (or early hay), pasture, sorghum, winter fallows and green manures
4)reduce seed rain by seed catching and harvesting early.
5)reduce seed carryover by burning stubbles as soon as possible after harvest.
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. 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 of 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.
Oats (Avena sativa) is awnless or has awns that are not twisted and 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.
Black, J.M. (1965). Flora of South Australia. (Government Printer, Adelaide, South Australia). P165-166.
Burbidge, N.T. and Gray, M. (1970). Flora of the Australian Capital Territory. (Australian National University Press, Canberra). p38. 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. Photo & seed diagram.
Harden, Gwen J. (1991). Flora of NSW. (Royal Botanic Gardens, Sydney). Volume 4. P589. 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). #150.6.
Mansooji, A.M. (1993). Herbicide resistance in wild oats Avena spp. PhD Thesis, The University of Adelaide.
Nietschke, B.S. (1996). Cultural weed management of wild oats. Plant Protection Quarterly 11:187-189.
Nietschke, B.S. and Medd, R.W. (1996). Chemical management of wild oats. Plant Protection Quarterly 11:190-191.
Paterson, J.G. (1977). Grasses in South Western Australia. (Western Australian Department of Agriculture Bulletin 4007). P27-28. Diagram.
Quail, P.H. and Carter, O.G. (1968). Survival and seasonal germination of seeds of Avena fatua and A. ludoviciana. Australian Journal of Agricultural Research 19, 721-9.
Thurston and Philipson (1976). quoted in Medd (1996).
Walsh, M.J. Biology and control of wild oats. GRDC final report, DAV 54, p1-22.
Wilson, B.J. and Phipps, P.A. (1985). A long term experiment on tillage, rotation and herbicide use for control of A. fatua in cereals. Proceedings of the British Crop Protection Conference, Brighton, England. p 693-700.
Acknowledgments:
Collated by HerbiGuide. Phone 08 98444064 or www.herbiguide.com.au for more information.