Photo guide to weeds

Parkinsonia (Parkinsonia aculeata)

  • Photo of Parkinsonia
    Parkinsonia flower
  • Photo of Parkinsonia
    Parkinsonia

General information

Thought to be native to tropical America, parkinsonia is a hairless shrub that has spread throughout the world as an ornamental and shade tree.

Parkinsonia is a Class 2 declared pest plant under Queensland legislation and a Weed of National Significance (WONS).

Scientific name

Parkinsonia aculeata

Similar species
  • Prickly acacia, mimosa bush, mesquite
Description
  • Hairless small tree growing up to 10m high.
  • Branches are slender, zig-zagged and have sharp spines.
  • Leaves have a short, spine-tipped stalk.
  • Leaf branches are 20-40cm long.
  • Flowers are yellow, fragrant, five-petalled, each on a long, slender drooping stalk.
  • Seed pods are pencil-like, 5-10cm long and constricted between seeds.
  • Seeds are oval, about 15mm long; have a thick and extremely hard coat remaining viable until favourable conditions occur.
Habitat
  • Occurs most abundantly on floodplains but adaptable to a wide range of soil types.
Distribution
  • Native to tropical America.
  • Found along watercourses in sub-humid and semi-arid areas of Queensland.
  • Infestations in the Gulf of Carpentaria Region and Fitzroy catchment are up to several kilometres across.
Life cycle
  • Flowers in early summer of its second or third year of growth then exploit variable seasonal conditions.
  • Pods mature in late summer and are readily dispersed by flood waters.
Spread
  • Spreads primarily by floodwaters.
  • Minor spread possible by mud sticking to vehicles and animals.
Impacts

Environmental

  • Forms dense, often impenetrable, thorny thickets along watercourses and bore drains.
  • Flooded country is particularly susceptible to invasion from floating seeds.
  • Provides a harbour for feral pigs, which predate on livestock, damage crops, and seriously degrade the environment.

Economic

  • Reduces pasture production.
  • Restricts stock access to drinking water and makes mustering virtually impossible.
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

Physical control

Fire

  • Fire can be effective. Kill rates may vary from 30% to 90% with best results obtained from slow moving grass fires that maintain heat around the base of plants for as long as possible.
  • Seedlings are most susceptible to fire, but moderate to high kills of larger plants can occur under the above mentioned conditions.
  • Spelling before burning to build a fuel load may be needed and controlling grazing pressure afterwards to re-establish a competitive pasture is recommended.

Mechanical control

  • Initial clearing by stick raking, blade ploughing or ripping is effective, however:
    - it is restricted to reasonably level areas away from watercourses
    - clearing will hasten seed germination, necessitating follow-up control either mechanically or chemically.

Herbicide control

Aerial application

  • Aerial application is undertaken using purpose-built applicators attached to aircraft. This technique is useful for dense, strategic infestations although it may be expensive on a broad scale and needs to be undertaken in accord with vegetation management legislation.

Foliar (overall) spray

  • This is an effective control method for seedlings up to 2 m tall. Spray leaf and stems to point of runoff. A wetting agent must be used.

Basal bark spray

  • For stems up to 15cm diameter, carefully spray around the base of the plant to a height of 30cm above ground level. Larger trees may be controlled by spraying to a greater height, up to 100cm above ground level.
  • Plants should be actively growing and preferably flowering. Field experience has shown that good soil moisture is essential for effective control.
  • Because parkinsonia infested areas are often subject to flooding, care is needed to ensure mud and flood debris does not prevent spray penetration to the bark. The trunk may need to be cleared before spraying.

Cut stump treatment

  • Can be performed at any time of the year. Cut stems off horizontally as close to the ground as possible. Immediately (within 15 seconds) swab or spray the cut surface and associated stem with herbicide mixture.

Soil application

  • Use one dose of herbicide per metre of tree height. Place doses close to tree trunk, either with spot gun on clear bare ground, or underground with ground injector. Rain or sufficient soil moisture is required before herbicide is taken up by the plant.
  • Do not use near watercourses or within a distance equal to at least twice the height of desirable trees.
  • See the parkinsonia fact sheet (PDF, 995.9KB) for herbicide control and application rates.

Biological control

  • Three species of insects have been introduced.
  • Both Penthobruchus germaini and Mimosetes ulkei are seed beetles that attack only parkinsonia and whose larvae destroy mature parkinsonia seeds. Penthobruchus germaini may be giving some control.
  • Parkinsonia leaf bug Rhinacloa callicrates is a small green bug imported from the USA.
  • Research has continued in recent years to survey the native range of parkinsonia for potential new agents. Several prospective insects have been identified by CSIRO. One of these a looper (Eueupithecia cisplatensis) has been approved for release in Australia.
  • Naturally occurring fungal pathogens have been identified as causing dieback within many infestations of parkinsonia across Northern Australia. Studies are continuing regarding the use of these pathogens as biological control tools.
Declaration details
  • 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 09 April 2013