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Class 3 - The plant must be fully and continuously suppressed and destroyed and the plant may not be sold, propagated or knowingly distributed.
Class 4 - The growth and spread of the plant must be controlled according to the measures specified in a management plan published by the local control authority and the plant may not be sold, propagated or knowingly distributed
Why Is It Bad?:
Chilean Needle Grass is recognised as one of Australia's top 20 worst weeds as a Weed of National Significance (WoNS). It is unpalatable and can reduce productivity by up to 50%. It is also highly invasive in natural environments such as grassy box woodlands. As such, it reduces biodiversity and out-competes native species.
Chilean Needle Grass develops a large, long-lived seed bank and so it is very difficult to eradicate. The seeds can injure stock and degrade the quality of wool and hides.
Chilean Needle Grass is also difficult to identify as it has similar traits to some native grass species as well as its relation, Serrated Tussock.
Chilean Needle Grass produces 'stem seeds' or cleistogenes as well as panicle seeds. These 'stem seeds' develop at the nodes and bases of stems
Leaf blades are 10-30cm long, 1-5mm wide, green to dark green. Margins are rough to touch.
Ligules are membranous, 1-3mm long with erect hairs on either side.
Inflorescences grow to 40cm in length, are loose and often drooping. Flowering stems can reach 1.2m in height.
Seeds are sharply-pointed, 6-10mm long with an awn 60-90mm long. The awn twists and kinks when dried out. There is a collar where the seed attaches to the awn, which is an important identifying feature.
Glumes mature to purple, giving the plant a distinctive colour during seeding. This colour fades as seeding finishes.
Fibrous with a thickened crown from where regrowth occurs.
Plants can be dug out; ensure the crown is included to prevent regrowth. No plant material should be left behind as 'stem seeds' will germinate, creating many new plants. All removed material should be incinerated or buried.
Fluproponate is registered for full use on Chliean Needle Grass while glyphosate is only registered for spot-spraying. Spot-spraying, boom-spray, wick wiping and spray topping are considered best practice. Autumn and winter are best for chemical application as these are generally the times when plants are actively growing.
Large infestations can be burnt to remove dead matter before treating regrowth with herbicide. This helps to protect any native species from off-target effects of chemical application. Fire alone will not kill Chilean Needle Grass, this method needs to be used in integration with other methods.
Slashing & Cutting:
Mowing with a catcher during flowering can minimise seed production however 'stem seeds' (which account for approximately 1/4 of seed production) will remain. This needs to be repeated when re-flowering occurs.
Flowering generally lasts 2 weeks; timing is essential as mowing after flowering will spread seeds greatly increasing infestation sizes.
All equipment should be cleaned thoroughly to prevent further spread
There are currently no biological control agents for Chilean Needle Grass in Australia.
The 'Defeating the Weeds Menace' program has invested in research being undertaken in Argentina where three Rust species have been identified as potential agents.
Grazing can be used in the winter months before seed set as feed value is at its highest at this time.
Paddocks with infestations should not be grazed during seeding as seeds can cause injuries and also livestock can spread the seeds, creating a bigger infestation.
Cultivation & Scalping:
Cultivation can be used to exhaust the soil seed bank. It MUST be followed by a repeat cultivation of herbicide treatment of seedlings, otherwise this method will only increase infestation sizes. A replacement species such as pasture, native grasses or summer crop must also be planted to compete with Chilean Needle Grass regrowth.
Mulching can help create a barrier to contain Chilean Needle Grass infestations but it cannot be used as a sole control method.
Maintaining strong competitive pastures or native plants will help prevent establishment of new Chilean Needle Grass plants, and reduce growth of existing plants.
Successful treatment programs rely on ongoing monitoring of sites. Regrowth and new seedlings can easily become larger infestations if follow-up treatments are not part of the management program