Mysore thorn (Caesalpinia decapetala)

Mysore thorn, also known as wait-a-while, is an aggressive prickly shrub that forms dense thickets. It invades environmental areas, creek banks, roadsides, pastures and bushland.

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How does this weed affect you?

Mysore thorn was originally planted in gardens as a hedge plant. It is now an environmental weed. Mysore thorn can affect the biodiversity of native bushland areas by out-competing and smothering native species. Its dense thickets can provide a harbour for feral animals, restrict the habitat available for native animals and inhibit access to water, roads and pasture. 

Where is it found?

Mysore thorn is native to Japan, China, India and Malaysia. It is present in many countries around the world and is an invasive weed in New Zealand, the Dominican Republic, South Africa and Hawaii.

Mysore thorn is predominantly located along the south-eastern Queensland coast. Scattered infestations occur in some southern inland locations and along most of Queenslands coast line.

In New South Wales many localised infestations—which continue to spread—occur in the north coast region. Small, localised infestations are also present along the central coast of NSW.

How does it spread?

Mysore thorn reproduces by seed, which may stay viable in the soil for up to 10 years. The seed is mainly dispersed by animals that feed on the fruit, such as rodents, birds and cattle. Seed pods float on water, spreading seeds downstream to new locations.

The branches of mysore thorn produce new roots when they come into contact with the ground, anchoring the plant into the soil. Plants will re-shoot vigorously when cut.

Lifecycle

Mysore thorn flowers during winter and spring. Fruits are produced from August through to December. 

What does it look like?

Mysore Thorn is a large evergreen shrub growing 2–4 m high, or up to 20 m high when climbing over supporting vegetation.

Branches

  • covered in fine golden hairs
  • hooked thorns up to 5 mm long occur along its length
  • bark is rough at the base, then smoother and cream-green above

Leaves

  • dark green above and paler underneath
  • bipinnate, consisting of a main stalk up to 30 cm long with 3–15 opposite pairs of pinnae
  • each pinna has 3–12 pairs of oblong leaflets (10–22 mm long and 4–11 mm wide)

Flower

  • pale yellow or whitish in colour
  • 5 petals, 10–15 mm long and 8–15 mm wide
  • on stalks 15–25 mm long
  • arranged in spike-like clusters at the tip of branches, up to 35 cm long

Pod

  • oblong, flat and hairy
  • 6–10 cm long and 2–3 cm wide
  • has a small projection (beak) at one end
  • split open when mature
  • contain 4–9 seeds

Seed

  • black and brown in colour
  • 6–10 mm wide

Habitat

Mysore thorn prefers humid coastal conditions in sub-tropical to tropical climates. Mysore thorn grows on a variety of soil types and will tolerate annual rainfalls from 300 to 3000 mm. It will often grow in disturbed areas, roadsides, pastures, creek banks, native grasslands and along the edges of bushlands and forests.

References

CABI invasive species compendium online data sheet. Caesalpinia decapetala (Mysore thorn). CABI Publishing 2011. www.cabi.org/ISC. Accessed August 2014.

Department of the Environment (2011) Weeds in Australia: Caesalpinia decapetala . Australian Government. www.environment.gov.au/biodiversity/invasive/weeds/identification/index.html. Accessed August 2014. 

Hosking JR, Sainty GR, Jacobs SWL & Dellow JJ (in prep) The Australian WeedBOOK

Parsons, WT and Cuthbertson, EG (2001) Noxious weeds of Australia, CSIRO Publishing, Collingwood.

Richardson FJ, Richardson RG and Shepherd RCH (2011) Weeds of the south-east: an identification guide for Australia. RG and FJ Richardson, Meredith, Victoria.

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Control

Any control activities for mysore thorn will need to be monitored and followed up with additional control measures as required.

Mechanical control

Only recommended for small plants and seedlings that can be manually pulled or hoed from the ground. Take care to remove all of the roots. Larger plants and infestations are difficult to treat in this way. The thorny habit of mysore thorn and ability to rapidly re-shoot from cut stems, makes mechanical control challenging.

Herbicide control

Treat when plants are actively growing and before flowering. In dense infestations, foliar applications repeated every 3–9 months will give the best results.

Herbicide options

WARNING - ALWAYS READ THE LABEL
Users of agricultural or veterinary chemical products must always read the label and any permit, before using the product, and strictly comply with the directions on the label and the conditions of any permit. Users are not absolved from compliance with the directions on the label or the conditions of the permit by reason of any statement made or not made in this information. To view permits or product labels go to the Australian Pesticides and Veterinary Medicines Authority website www.apvma.gov.au

See Using herbicides for more information.


Metsulfuron-methyl 300 g/kg + Aminopyralid 375 g/kg (Stingerâ„¢)
Rate: 20 g per 100 L of water
Comments: Hand gun application.
Withholding period: 3 - 56 days (see label)
Herbicide group: B, Inhibitors of acetolactate synthase (ALS inhibitors) + I, Disruptors of plant cell growth (synthetic auxins)
Resistance risk: High/Moderate


Metsulfuron-methyl 600 g/kg (Brush-off®)
Rate: 10 g per 100 L of water
Comments: Spray to thoroughly wet all foliage, but not to cause run off. Apply to actively growing plants before flowering. Add wetting agent.
Withholding period: Nil (recommended not to graze for 7 days before treatment and for 7 days after treatment to allow adequate chemical uptake in target weeds).
Herbicide group: B, Inhibitors of acetolactate synthase (ALS inhibitors)
Resistance risk: High


Picloram 44.7 g/kg + Aminopyralid 4.47 g/L (Vigilant II ®)
Rate: Undiluted
Comments: Cut stump/stem injection application. Apply a 3–5 mm layer of gel for stems less than 20 mm. Apply 5 mm layer on stems above 20 mm .
Withholding period: Nil.
Herbicide group: I, Disruptors of plant cell growth (synthetic auxins)
Resistance risk: Moderate


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Biosecurity duty

The content provided here is for information purposes only and is taken from the Biosecurity Act 2015 and its subordinate legislation, and the Regional Strategic Weed Management Plans (published by each Local Land Services region in NSW). It describes the state and regional priorities for weeds in New South Wales, Australia.

Area Duty
All of NSW General Biosecurity Duty
All plants are regulated with a general biosecurity duty to prevent, eliminate or minimise any biosecurity risk they may pose. Any person who deals with any plant, who knows (or ought to know) of any biosecurity risk, has a duty to ensure the risk is prevented, eliminated or minimised, so far as is reasonably practicable.
Greater Sydney Regional Recommended Measure*
The plant should be eradicated from the land and the land kept free of the plant. The plant should not be bought, sold, grown, carried or released into the environment.
Hunter Regional Recommended Measure*
Land managers should mitigate the risk of new weeds being introduced to their land. The plant should be eradicated from the land and the land kept free of the plant. The plant should not be bought, sold, grown, carried or released into the environment. Notify local control authority if found.
North Coast
Exclusion zone: all lands in the region except for the core infestation area of Richmond Valley Council, Ballina Shire Council, Lismore Council, Kyogle Council, Byron Shire Council and Tweed Shire Council.
Regional Recommended Measure*
Whole region: The plant or parts of the plant should not be traded, carried, grown or released into the environment. Exclusion zone: The plant should be eradicated from the land and the land kept free of the plant. Land managers should mitigate the risk of the plant being introduced to their land. Core infestation area: Land managers should reduce impacts from the plant on priority assets.
South East
Exclusion zone: whole region except the core infestation area of Wollongong
Regional Recommended Measure*
Whole region: Land managers should mitigate the risk of new weeds being introduced to their land. Plant should not be bought, sold, grown, carried or released into the environment. Exclusion zone: The plant should be eradicated from the land and the land kept free of the plant.
*To see the Regional Strategic Weeds Management Plans containing demonstrated outcomes that fulfill the general biosecurity duty for this weed click here

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Reviewed 2017