Photo guide to weeds

Mesquite (Prosopis spp.)

  • Photo of Mesquite
    Mesquite flower
  • Photo of Mesquite
    Mesquite plant

General information

There are three known species of mesquite plus a hybrid present in Queensland. Mesquite, once a favoured shade tree around homesteads, has spread significantly in Queensland.

Mesquite (all Prosopis spp. and hybrids) are Class 1 declared pest plants under Queensland legislation and a Weed of National Significance.Prosopis glandulosa, P. pallida and P. veluntina are Class 2 declared plants.

Biosecurity Queensland encourages people report this pest plant and take actions to help stop the establishment, prevent the spread, and to control this pest.

Overview

Scientific name

Prosopis glandulosa, P. pallida, P. velutina and P. spp. hybrid

Other names
  • Algaroba, Quilpie algaroba
Description
  • Small branches have smooth, dark-red or green bark and a zigzag shape.
  • Fernlike leaves, 1-4 pairs of leaf branches, 6-18 pairs of individual leaflets.
  • Dark-green foliage but can vary to bluish-green.
  • Paired thorns occur just above each leaf axil.
  • Seed pods are 10-20cm long, straight to slightly curved, smooth, with slight constrictions between the seeds.
Habitat
  • Found along waterways, floodplains, roadsides and in horse paddocks near homesteads.
Distribution
  • Native to North and South America.
  • Introduced into Australia as an ornamental and used for shade in soil stabilisation programs.
Life cycle
  • Extended flowering may occur August - December with pod formation during October - March.
  • Long lived plant.
Spread
  • Spreads by dispersal of seeds in the faeces of stock, some pest and native animals.
Impacts

Environmental

  • Forms dense, impenetrable thickets.
  • Out-competes other vegetation.
  • Quickly invades upland country.

Economic

  • Dense infestations eliminate pasture production.
  • Interferes with mustering and blocks access to watering places.
  • Sharp thorns can puncture vehicle tyres.

Social

  • Sharp thorns can injure animals and humans.
Prevention
  • The best form of weed control is prevention. Treat weed infestations when they are small - do not allow weeds to establish.
  • Ways to prevent weed spread
Control

Mechanical control

Stick raking

  • Effective on medium to high density infestations of Prosopis pallida, particularly if a cutter bar is attached to the bottom of the stick rake. Best results are achieved when soil moisture is sufficient to allow machinery to work with minimum strain, but soil is dry enough so the root system desiccates (late autumn/winter for a normal wet season).

Pushing

  • Dozer pushing of the singled stemmed Prosopis pallida has been effective around Cloncurry and Hughenden. Little suckering results although some seedling emergence will be promoted. Not so effective on multi-stemmed species as they often break of at ground level and reshoot vigorously.

Chain pulling

  • Chain pulling using dozers may kill a high proportion of trees in a Prosopis pallida infestation. However, the effectiveness of control may be reduced when either very dense infestations or a high proportion of young trees and seedlings are present.
  • Fire is often necessary as a follow-up measure to pulling and paddocks may need to be rested from grazing to allow a build-up of grass. It is better if burning can be delayed until seedlings have germinated as they will then be destroyed in the fire. Chain pulling is best undertaken from July to October.
  • Chain pulling on its own is not effective  on Prosopis velutina or other multi-stemmed species (including hybrids) due to their growth structure and potential for regrowth at the root system.

Blade ploughing

  • Either a front mounted or rear mounted blade plough can be used on all mesquite species.
  • Front mounted Ellrott blade ploughs have proven extremely effective in controlling hybrid mesquite at McKinlay and Prosopis velutina at Quilpie.
  • Trial work using a 4.2 m Homan rear mounted blade plough on Prosopis velutina has proven to be extremely effective, giving very high kill rates on the treated area.

Fire

  • Effective against Prosopis pallida in the Cloncurry and Hughenden areas. Burnt Prosopis pallida have died quickly, with the bark splitting away from the trunk a few weeks after the fire. Both mature trees and seedlings are susceptible.
  • However, it is often not possible to kill a complete infestation because rarely is there an even distribution of fuel across a whole site.
  • Multi-stemmed species appear to be more tolerant of fire and reshoot from the base afterwards. 

Herbicide control

Foliar spraying

  • Effective method for the control of seedlings up to 1.5m tall.
  • Spray leaf and stems to the point of runoff. A wetting agent must be used.
Basal bark
  • Spray around the base of the plant to a height of about 30cm above ground level.
  • Thoroughly spray all crevices and each stem of multi-stemmed trees. Larger trees may be controlled by spraying to a greater height, up to 100cm above ground level. The best time to spray is during autumn when plants are actively growing and soil moisture is good.

Cut stump

  • Cut stems off horizontally as close to the ground as possible and immediately (within 15 seconds) swab the cut surface with the herbicide mixture. This treatment can be used at any time of the year.
  • Mesquite fact sheet (PDF, 708.4KB) for herbicide control and application rates.

Biological control

Four species of insects have been introduced as biological control agents against mesquite.

  • The larvae of the seed beetles Algarobius bottimeri and Algarobius prosopis destroy mesquite seeds in mature pods both in the trees and on the ground. Only A. prosopis has been found in more recent surveys and this beetle is unlikely to be having much effect.
  • Prosopidopsylla flavais a sap-sucking psyllid that causes dieback. It appears to prefer cooler climates and may be present in small populations in south-western Queensland.
  • The leaf-tying moth Evippe spp. has established at all release sites, but is most abundant in northern Queensland where it is causing moderate defoliation.
Declaration details

All Prosopis spp. and hybrids not yet found in Queensland are Class 1 declared species. Prosopis glandulosa, P. pallida and P. veluntina are Class 2 declared pest plants.

  • A declared Class 1 species under the Land Protection (Pest and Stock Route Management) Act 2002.
  • Not commonly present or established in Queensland and has the potential to cause impacts to whole or part of the State.
  • Introduction, keeping, releasing and supplying (including supplying things containing reproductive material of this pest) is not possible without a permit, for special purposes, issued by Biosecurity Queensland.
  • A declared Class 2 species under the Land Protection (Pest and Stock Route Management) Act 2002.
  • Taking for commercial use, introduction, keeping, releasing and supplying (including supplying things containing reproductive material of this pest) is prohibited without a permit issued by Biosecurity Queensland.
  • Landholders are required to control declared pests on their properties.

Last updated 03 May 2013