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Poverty weed (Iva axillaris)

Poverty weed is a strong agricultural competitor that can reduce crop yields and threaten pasture. It has a very limited Australian distribution, with former South Australian sites eradicated and known Victorian records concentrated in a few areas.

Key facts

Type: Weed, herb.

Native to: Western North America, mainly west of the Continental Divide.

Established in: VIC, SA.

Other names: Death Weed, Devil's Weed, Mouse-ear Poverty Weed, Poverty Sumpweed.

Best time to act: Look for new shoots in spring and flowering plants in summer; summer during active growth is the stated period for herbicide treatment.

Identification

  • This perennial herb usually grows 20 to 40 cm high and forms colonies from extensive underground rhizomes.
  • Its stems are branched near the base, often partly trailing there, and then grow upright.
  • The stiff, grey-green leaves are mostly 10 to 30 mm long, have smooth margins and give off a strong unpleasant odour when crushed.
  • Small greenish-yellow flower heads droop on short stalks in the forks of the upper leaves.
  • Look-alike: It may resemble the native Centipeda cunninghamii and Centipeda minima, but both have toothed leaf margins and neither has drooping flower heads.
  • Look-alike: Centipeda minima also has a more creeping growth habit.

Where it grows

In Australia it has been reported from neglected vineyards, orange groves, pasture, cropping land and roadsides, in areas receiving 300 to 600 mm of annual rainfall.

Why it matters

  • Its extensive rhizomes allow it to compete strongly with crops, especially cereals, for water and nutrients, and it can reduce crop yields.
  • The plant and its roots and rhizomes are reported to reduce the germination of other species, posing a potential threat to crops and pasture.
  • It can form clonal colonies that may displace native grasses and forbs in open, disturbed areas, and may threaten saline ecosystems.
  • Above-ground growth dies in autumn, leaving potential for surface soil erosion; the plant is rarely grazed because of its disagreeable scent.

How it spreads

  • It reproduces mainly by rhizome and root fragments; seeds are rarely viable and are not adapted for wind dispersal.
  • Machinery can drag rhizome fragments from infested areas into clean areas.
  • Movement of contaminated agricultural seed, grain, forage, fodder and soil can also contribute to spread.

Control options

  • Herbicides appear to offer the main effective control; use registered herbicides and follow product directions.
  • Avoid cultivation because it can spread root fragments; mowing is ineffective because plants regrow.
  • Hand pulling is difficult and can leave viable roots, so regrowth may require repeated attention; wear gloves because plants may cause allergic symptoms.

Hygiene and washdown

  • Clean soil and crop debris from machinery, clothes and shoes before moving between fields and farms.
  • Restrict movement of soil, machinery and agricultural materials from infested areas, particularly where they may carry rhizome fragments.
  • 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: State prohibited weed. State prohibited weeds are the highest priority: the Victorian Government is responsible for eradicating them, so report any sighting to Agriculture Victoria.
  • South Australia: Not declared. Not declared under the Landscape South Australia Act 2019. Other laws may still apply.
  • Western Australia: Permitted, not declared. Listed as a permitted organism in WA, so it can be brought in, but it is not a declared pest.
  • 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.

  • 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