Mesquite

Mesquite is a declared Class A and Class C weed and a Weed of National Significance.

Go to the Weeds of National Significance website for more information.

Mesquite also has a statutory weed management plan (1.2 mb) which outlines the legal requirements for control.

Another name for this plant is Prosopis spp.

Mesquite - infestation

Identification

You should use this as a guide. There may be other plants or weeds that look similar.

If you are unsure, contact the Weed Management Branch.

Habit

These features describe the habit of this plant:

  • single or multi-stemmed tree or shrubby bush
  • spreading canopy
  • 3 to 15m tall.

Mesquite - habit

Stems and branches

These features can identify the stems and branches:

  • zig-zag structure
  • single branches extend outside the main canopy
  • mostly thorny
  • thorns ranging from 0.4 to over 7.5cm long.

Mesquite - stems and branches

Leaves

These features can identify the leaves:

  • leaves occur at each point where the branch changes direction
  • twice-divided
  • one to four pairs of primary leaflets
  • each leaflet has seven to 21 pairs of small opposite secondary leaflets.

Mesquite - leaves

Flowers

These features can identify the flowers:

  • greenish yellow
  •  forming a cylindrical flower head
  • flower head is 5 to 8cm long
  • flowers of all mesquite varieties have similar characteristics.

Mesquite - flowers

Fruit and seeds

These features can identify the fruit and seeds:

  • pods are 12 to 20 cm long
  • straight or slightly curved
  • slight constrictions between the 10 to 20 enclosed seeds.

Mesquite - fruit and seeds

Similar looking plants

The following plant species look similar to mesquite:

Mimosa bush 

Mimosa bush (Acacia farnesiana) is native to Central and South America. It is a rounded shrub or small tree that forms thorny thickets that hinder mustering and stock access to water. It is not a declared weed in the NT.

This table (95.3 kb) can help you to identify a prickle bush that might be mimosa.

Impact

Pastoralism is the main land use in areas most susceptible to mesquite invasion. 

Severe mesquite infestations can reduce the production of native and introduced pasture species by up to 90%. 

Increased costs associated with mustering and weed control can have large impacts on industry profitability. Thorns can also damage vehicle tyres and injure animals and workers.

Mesquite can have all of the following impacts:

  • forms dense, impenetrable thickets
  • reduces biodiversity and ecological function
  • invades and replaces native plant communities and habitat for wildlife
  • reduces carrying capacity
  • restricts mustering
  • thorns are sharp and can cause injury and equipment damage.

Habitat and distribution

Native to North and South America, mesquite was introduced to Australia more than 100 years ago, where it was widely planted as a shade tree throughout western Queensland and north-western Western Australia. 

It was also used as a soil stabiliser around mine sites in Queensland and New South Wales. Mesquite is now present in all mainland states.

In the Northern Territory mesquite occurs as scattered, isolated, low level infestations across multiple regions including Arnhem Land, the Victoria River District (VRD), the Barkly Tableland and the Alice Springs region. 

On the Barkly Tableland low level infestations occur on at least 12 pastoral leases. 

These infestations are current management priorities as further spread and establishment into clean areas is a significant risk. Scattered plants found in the VRD and Alice Springs region are managed as recorded/detected.

Spread prevention

Cattle are a major cause of mesquite spread in the Northern Territory, but seeds are also readily spread by water flow (rain, floods), feral animals and vehicles.

You can prevent the spread of mesquite by doing all of the following:

  • map infestations to help develop a management plan
  • control minor infestations, isolated outbreaks or seedlings first
  • isolate and monitor newly transported stock, particularly those coming from Queensland, Western Australia or other properties with known mesquite infestations
  • prevent grazing in areas where mature pods are available, potentially by fencing strategically to contain infestations
  • isolate and monitor stock which are being moved from infested paddocks to clean paddocks
  • eradicate all known mesquite plants and infestations
  • implement early detection and eradication programs
  • design and implement a spread prevention program
  • designate wash down areas and actively work to prevent contamination of clean areas
  • monitor areas that you have treated and watch for re-infestations.

Mesquite - spread

Control

Mesquite in small, isolated groups is easy to control, but long-term monitoring and follow-up control programs must be done to stop re-establishment from seed banks that can stay viable for more than 10 years.

Chemical control

The best time to treat mesquite is from March to May. Below is a list of treatment methods that can be used.

Chemical and concentration Rate Situation, method and notes
Aminopyralid 8 g/L + Triclopyr 300 g/L + Picloram 100 g/L
Grazon® Extra
200mL / 100 L Seedling (individuals and infestation):
Foliar spray - non-ionic wetting agent required - do not spray plants bearing pods
Aminopyralid 8 g/L + Triclopyr 300 g/L + Picloram 100 g/Ls
Various trade names
350mL / 100 L Seedling (individuals and infestation):
Foliar spray - non-ionic wetting agent required - do not spray plants bearing pods
Triclopyr 240 g/L and Picloram 120 g/L
Access®

1 L / 60 L (diesel)
1 L / 60 L (diesel)
Adult (individuals or infestation):
Basal bark < 5cm stem diameter
Cut stump > 5cm stem diameter

Basal bark treatments are best administered during the active growing season. 

This method involves spraying around the whole stem up to 300mm from the ground.

Cut stump treatments can be undertaken at any time of year, but are best administered during the active growing season. 

This method involves applying herbicide to a newly cut stump immediately following chain sawing.

Non-chemical control

Hand pulling and grubbing

Weeds, including their roots, are physically pulled out of the ground by hand or using hand tools. This is an effective method of control for individual weeds and recent outbreaks that haven’t released seeds yet, but it requires a lot of labour.

Blade ploughing

A blade plough is used to push over some woody shrubs and sever their roots underground. 

Bulldozing

Bulldozers, chopper rollers or graders are used to clear large weed infestations. This leaves large areas of soil exposed so follow up control or revegetation must be considered.

Last updated: 27 June 2017