Mesquite (Prosopis species)

Mesquite is a woody weed that invades open grasslands, rangelands and the banks of watercourses by forming impenetrable, thorny thickets.

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How does this weed affect you?

Mesquite is a woody weed that invades open grasslands, rangelands and the banks of watercourses, forming thick, impenetrable, thorny thickets. There are four known species of mesquite in Australia and several hybrids. 

Mesquite has a long lifecycle, very high seed production, the ability to survive droughts and long seed dormancy. These features make it an exceptionally resilient plant that can quickly take advantage of suitable environments and dominate entire ecosystems. Its deep taproot and extensive root system allow it to thrive in hot and dry conditions.

Where is it found?

Mesquite is native to the America’s from southern USA through to northern South America. In its native range its timber is used for fence posts, woodworking and fuel. It has become an invasive weed in many parts of the world including South Africa, Hawaii, West Indies, Iraq, India, Pakistan, Sri Lanka and parts of Africa. It has also become invasive in areas of its native range, particularly southern USA.

Originally planted as a fodder, shade and ornamental tree in northern Australia, mesquite was also planted around mining sites for soil stabilisation and dust reduction. It has now spread throughout mainland Australia, with the worst infestations occurring in the Pilbara region of Western Australia, the Barkly Tablelands of the Northern Territory and western Queensland.

In New South Wales (NSW), infestations of mesquite have mostly occurred throughout the Broken Hill and Milparinka areas, with isolated plants found in the south-western Riverina district and in the north-western areas of Gilgandra, Coonamble and Bourke. Mesquite has the potential to invade all areas of western NSW.

How does it spread?

Mesquite reproduces by seed which is dispersed when livestock feed on seed pods (seeds pass through the digestive tract and remain viable), and when pods and seeds move in flood waters. Native and feral animals also assist in spreading mesquite by eating the sugar- and protein-rich seed pods.

Each plant is capable of producing thousands of seeds per year that can remain dormant in the soil for very long periods. Seeds will only germinate once the hard outer casing has been damaged allowing moisture into the seed. Animal consumption, fire and wet conditions can effectively damage the seed casing and trigger germination.

To reduce the risk of spread it is recommended that during summer months livestock be removed from paddocks where mature seed pods are available; and be quarantined from mesquite areas for at least one week before being transported.

What does it look like?

Mesquite can be either a single-stemmed tree (up to 15 m in height) or a multi-stemmed shrub with drooping branches (3–5 m high). The whole plant has an untidy appearance with single branches extending outside of the main canopy.

Key identification features

  • Branches have a characteristic zig-zag shape. Bark is smooth and dark red-green in young stems, and rough and grey in older stems.
  • Fern-like leaves occur at each point where the branch changes direction and contain 1–4 pairs of leaf branches.
  • A pair of spines, 4–75 mm long, normally arise above each leaf stalk or along the main stem.
  • Flowers are a greenish cream-yellow, 5–8 cm long and cylindrical in shape, resembling a ‘lamb’s tail’. Flowers appear in spring and early summer.
  • The seed pod is smooth, up to 20 cm long with slight constrictions between each seed. Each pod contains 5–20 seeds and varies in colour from green when young to either straw-coloured or purplish when mature.

Acknowledgements

Adapted from CRC Weed Management Guide (2003) Mesquite; Reviewed by: Peter Gray; Edited by: Elissa van Oosterhout.

References

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

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Control

Mesquite can be managed by a variety of control methods. The control program for mesquite will depend on the size of the infestation and the species present.

Identification of mesquite can be difficult due to the variations in growth from. If you suspect you have found mesquite contact your local council weeds officer who will assist with identification, removal and eradication.

Biological control

Four biological control agents have been released in NSW for mesquite control. Two seed beetles (Algarobius propsopis and Algarobius bottimeri), a leaf tier (Evippe sp.) and a psyllid (Prosopidopsylla flava). A fifth agent, a stem borer (Oncideres rhodosticta) is under investigation and has not yet been released. 

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.


Picloram 100 g/L + Triclopyr 300 g/L + Aminopyralid 8 g/L (Grazon Extra®)
Rate: 350 mL in 100 L of water
Comments: Controls seedlings, plants in full leaf and flowering before podding. Thoroughly wet all foliage, stems and soil around the base of the plants. Add a wetting agent to increase efficacy. Do not spray plants bearing pods.
Withholding period: Where product is used to control woody weeds in pastures there is a restriction of 12 weeks for use of treated pastures for making hay and silage; using hay or other plant material for compost, mulch or mushroom substrate; or using animal waste from animals grazing on treated pastures for compost, mulching, or spreading on pasture/crops.
Herbicide group: I, Disruptors of plant cell growth (synthetic auxins)
Resistance risk: Moderate


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


Triclopyr 240 g/L + Picloram 120 g/L (Access™ )
Rate: 1.0 L in 60 L of diesel
Comments: Basal bark application of plants up to 5 cm in diameter. Cut stump for plants over 5 cm.
Withholding period: Nil
Herbicide group: I, Disruptors of plant cell growth (synthetic auxins)
Resistance risk: Moderate


Triclopyr 300 g/L + Picloram 100 g/L (Grazon® DS)
Rate: 350 mL in 100 L of water
Comments: Controls seedlings, plants in full leaf and flowering before podding. Thoroughly wet all foliage, stems and soil around the base of the plants. Add a wetting agent to increase efficacy. Do not spray plants bearing pods.
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.
All of NSW Prohibition on dealings
Must not be imported into the State or sold
All species in the genus Prosopis have this requirement
Central West Regional Recommended Measure*
Land managers should mitigate the risk of the plant being introduced to their land. The plant should be eradicated from the land and the land kept free of the plant.
Murray 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. Notify local control authority if found.
North West
An exclusion zone is established for all lands in the region, except the core infestation area comprising the Walgett Shire council
Regional Recommended Measure*
Whole of region: The plant should not be bought, sold, grown, carried or released into the environment. Exclusion zone: 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. Core infestation: Land managers reduce impacts from the plant on priority assets
Riverina 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. Notify local control authority if found.
Western
Exclusion zone: whole region except for the core infestation area of Evelyn, Yantara, Mootwingee, Yancowinna, Menindee, Tandora, Livingstone and Windeyer counties
Regional Recommended Measure*
Whole region: Land managers should mitigate the risk of the plant being introduced to their land. Exclusion zone: The plant should be eradicated from the land and the land kept free of the plant. Core infestation area: Land managers should mitigate spread from their land.
*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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For technical advice and assistance with identification please contact your local council weeds officer.
For further information call the NSW Invasive Plants and Animals Enquiry Line on 1800 680 244 or send an email to weeds@dpi.nsw.gov.au

Reviewed 2017