Erect, tufted, annual grass crop with hollow stems to 2 m tall.
The loosely branched inflorescence has large drooping spikelets, each with 2 or 3 florets. The seed is usually yellow.
Description:
Cotyledons:
One. Usually underground.
Leaves:
Emerging leaf rolled in the bud.
Blade - Flat, 150-700 x 5-12mm. Hairless to slightly hairy. Tip pointed. Rough to touch.
Sheath - Loose. Rolled and overlapping.
Ligule - Membranous, short and jagged.
Auricles - None.
Stems:
300-2000 mm. Erect. Usually many. Hollow. Solid nodes. Unbranched.
Flower head:
Loose, branched, panicle, pyramidal in outline, 50-300 mm long. Retains seed for some time after ripening.
Flowers:
Usually in pairs, 19-25 mm long.
Spikelets - Usually 2 flowered.
Florets - First floret often with dorsal awn, second floret often awnless. Second floret attached quite strongly to the first.
Glumes - Striped. 20-30 mm long.
Lemma - Hairless or with a few hairs at the base. 2 terminal, short, acute teeth. Awnless or with a straight awn 10-19 mm long that is scarcely twisted.
Awn - twice as long as the spikelet.
Stamens -
Anthers - Yellow.
Seeds:
Yellow. Seeds on slender stalks. Fine hairs on seed cause itching. 10-15 mm long by 2-5 mm wide. Awns if present are not twisted.
Roots:
Fibrous.
Key Characters:
Lemmas generally hairless.
Awns if present are not twisted.
Seed is yellow.
Biology:
Life cycle:
Annual. Germinates in Autumn/winter. Flowers in spring.
Reproduction:
Flowering times:
September to May.
Seed Biology and Germination:
Little dormancy.
Vegetative Propagules:
None.
Hybrids:
Many cultivars have been formed from hybrids.
Allelopathy:
Stubble is allelopathic.
Population Dynamics and Dispersal:
Spread by seed.
Origin and History:
Europe.
Distribution:
ACT, NSW, QLD, SA, TAS, VIC, WA.
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:
Cultivated crop. Fodder. Human food.
Detrimental:
Weed of other crops.
Toxicity:
May cause grain poisoning if large amounts of grain are consumed by stock.
Nitrate Poisoning.
Young growing crops and those with much stem may cause nitrate poisoning in stock especially if they have been fertilised with nitrogenous fertiliser, are growing rapidly after a dry spell or have been affected by barley yellow dwarf virus. Cattle are more susceptible than sheep. Most cases of toxicity occur between April and September.
Oaten hay and stubble may also cause nitrate poisoning.
Grass Tetany.
This is caused by a magnesium deficiency. Young lush oats are low in magnesium and this is made worse by application of nitrogenous or potash fertilisers. Cattle and sheep are affected.
Fodder crop poisoning complex.
Occasionally occurs when 150-200 mm tall oat crops are fed off to induce better tillering.
Rickets and bone fragility
Induced by an anti vitamin D factor in young oats. Lambs and ram hoggets are the most susceptible.
Photo-sensitisation
Affects cattle, sheep, goats and rarely pigs. Most cases occur between April and October.
Smutty Oats
Poisoning associated with feeding oats infected with the smut fungus have occurred overseas but not in Australia.
Symptoms:
Nitrate poisoning.
Grass Tetany.
Fodder crop poisoning complex.
Rickets and bone fragility
Photo-sensitisation
Treatment:
Nitrate poisoning.
Don't allow hungry stock to avidly graze oats, especially in cold weather.
Grass tetany.
For prevention, feed supplementary hay and provide magnesium supplements.
Fodder crop poisoning complex.
Remove stock from oats.
Rickets and bone fragility
Intra muscular injection of Vitamin D.
Photo-sensitisation
Provide shade. Locally treat with Condy's crystals, Bismarck or nigrosin.
Legislation:
None.
Management and Control:
There are a number of herbicides that provide selective control in most crops.
In non agricultural situations
Prevent seed set for 2-3 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.
Thresholds:
1 plant/m2 is sufficient to contaminate grain.
10-20 plants/m2 causes around 10% yield loss in cereals.
Eradication strategies:
Oats has little seed dormancy and the control techniques above will generally lead to local eradication in a few years.
Herbicide resistance:
None reported.
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.
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:
Oats are distinguished from other wild oats by the attachment of the glume to the seed, much longer retention of seed in the head, florets are hairless and shortly 2 toothed at the tip and the awns are barely twisted or absent.
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.
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Lamp, C. and Collet, F. (1990). A Field Guide to Weeds in Australia. (Inkata Press, Melbourne).
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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.