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African rue (Peganum harmala)

African rue competes with native shrubs and grasses for moisture and nutrients, and can affect pasture production in rangelands. It is difficult to control once established and can poison livestock, particularly during drought, although its bitter taste makes it highly unpalatable to stock.

Key facts

Type: Weed, herb.

Native to: Native to Spain and a range extending from northern Africa to Tibet..

Established in: NSW, VIC, SA.

Other names: Syrian Rue, Wild Ru, Peganum, Harmal.

Best time to act: Look for germinating plants from early spring and treat with registered herbicides before flowering or during early flowering; flowering runs from late spring to early autumn, with a peak in November and December.

Identification

  • It is an erect, much-branched perennial herb or shrub, usually 30 to 80 cm high, with smooth, stiff stems.
  • Its bright green, somewhat succulent leaves are 2 to 5 cm long and divided into three or more narrow linear segments.
  • Solitary white to cream flowers, about 2.5 cm across, grow on slender stalks.
  • Its rounded, flattened capsules are 8 to 12 mm across and contain 45 to 60 thin, angular seeds that are brown to black.

Where it grows

In Australia it occurs mainly in south-eastern South Australia, with occasional records in southern New South Wales and northern Victoria, often on roadsides, waste areas, cultivated land, pastures, rangelands and grasslands.

Why it matters

  • It competes with native shrubs and grasses for moisture and nutrients, affecting pasture production in rangelands.
  • It can germinate earlier in spring than native plants and has an allelopathic effect that inhibits the germination and growth of some plants.
  • All parts of the plant contain alkaloids and can be toxic to livestock, especially during drought; consumption can reduce fertility and cause abortions.
  • It is a known agricultural seed contaminant, while its overall effect on native plant communities is unknown.

How it spreads

  • Most seeds fall near the parent plant, but water flowing over soil, mud carried by animals or vehicles, and animals eating the fruit can disperse them.
  • The plant can also spread by suckering from its roots.
  • Rootstock moved to new areas during cultivation can establish plants there.

Control options

  • Individual plants can be dug out and burned, but remove the root system thoroughly because fragments left in the soil can regrow.
  • Established plants have extensive roots, with the taproot recorded to reach 2.5 m and lateral roots to more than 3 m, so chemical control is considered more efficient.
  • Use registered herbicides on the leaves before flowering, repeating applications as required until the plants are killed.
  • A knock-down herbicide applied during early flowering can control most above-ground growth; surviving seedlings and roots may emerge later because the herbicide has no residual properties.

Hygiene and washdown

  • Clean soil and mud from vehicles and machinery before leaving infested sites, as seed can be carried in mud tracked by vehicles.
  • Avoid moving infested rootstock during cultivation, as this can spread the plant to new areas.
  • Inspect and clean vehicles, plant and footwear before leaving an infested area, paying attention to tyres, radiators, belly plates, tracks and floor mats.
  • Wash down at a designated bay where runoff is contained and can be monitored for seedlings.
  • Record each washdown so the client has evidence of clean entry and exit.

Classification by state

  • Australia (national): No national listing. Managed under state and territory law.
  • Queensland: Not prohibited or restricted. Not listed as prohibited or restricted matter in Queensland. Everyone must also take all reasonable and practical steps to minimise its risks (the general biosecurity obligation).
  • New South Wales: Not a priority weed. Not a state or regional priority weed in NSW. The general biosecurity duty applies: anyone dealing with it must prevent, eliminate or minimise the risk it poses.
  • Victoria: Not declared. Not declared under the Catchment and Land Protection Act 1994. Other Victorian laws may still apply.
  • South Australia: Declared plant. Depending on the declaration, it can be an offence to move it on public roads or sell it, and landowners may be required to control it on their land.
  • Western Australia: Declared pest (C1), prohibited. C1 Exclusion: to be kept out of WA, or out of the parts of WA where it is not established. Report any sighting to DPIRD. It must not be brought into WA (prohibited organism).
  • Tasmania: Not declared. Not a declared weed in Tasmania. Other laws may still apply.
  • Northern Territory: Not declared. Not on the NT A to Z weed list, and Weeds Australia does not list it as declared in the NT. Check the NT declared weeds list before moving or planting it.
  • Australian Capital Territory: Not declared. Not declared under the Biosecurity Act 2023 (ACT). A general biosecurity duty still applies.

Legal obligations

Every state and territory places a duty on landholders and people working on land to prevent the spread of invasive species, such as the general biosecurity obligation in Queensland and the general biosecurity duty in New South Wales. Declarations and control requirements differ between states and local government areas, so check the current official list before work starts.

  • New South Wales: Biosecurity Act 2015 (NSW), administered by NSW Department of Primary Industries and Regional Development
  • Victoria: Catchment and Land Protection Act 1994 (Vic), administered by Agriculture Victoria
  • South Australia: Landscape South Australia Act 2019 (SA), administered by the regional landscape board

Sources