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Spiked pepper (Piper aduncum)

Spiked pepper is naturalised on Christmas Island but is not known to occur on the Australian mainland. It could become a serious pest in warm, moist tropical regions of northern Australia, where it can form dense thickets that exclude other vegetation.

Key facts

Type: Weed, shrub.

Native to: Tropical South and North America and the Caribbean Islands.

Established in: .

Other names: Stilt Root Piper, Matico, False Kava, Bamboo Piper.

Identification

  • A multi-stemmed shrub or small tree, usually 1–7 m tall, with smooth grey to green bark and sometimes prop roots supporting the lower trunk.
  • Crushed leaves and twigs have an aromatic odour; stems and branches have swollen purplish nodes.
  • Leaves grow alternately in two rows and are elliptic to lance-shaped, 12–22 cm long and 4–8 cm wide, on very short stalks of 2–7 mm.
  • The upper leaf surface is green and rough, while the pale green underside has short, soft hairs.
  • Minute white to pale yellow flowers grow on spikes about 10–12 cm long; fruiting spikes hold numerous berries that turn black when ripe.
  • Look-alike: The native Piper umbellatum is also a shrub, but has large heart-shaped leaves on stalks up to 30 cm long; spiked pepper has lance-shaped leaves on stalks only 2–7 mm long.

Where it grows

In Australia, spiked pepper is known to be naturalised on Christmas Island and has not been recorded on the mainland.

Why it matters

  • It can invade agricultural land and natural landscapes, forming dense thickets that exclude other vegetation.
  • It has the potential to become a serious pest in the warm, moist tropical regions of northern Australia.

How it spreads

  • It spreads mostly by seed: birds, fruit bats and other animals eat the small, single-seeded berries and disperse the seeds.
  • Seeds can also be dispersed by wind or as contaminants on machinery.
  • It can spread short distances by suckering from the rootstock and form large, dense clumps.

Control options

  • Small plants can be pulled by hand or dug out.
  • Remove the entire plant because it can regenerate from the rootstock and stem fragments.
  • Larger plants can be treated by foliar spraying or basal bark application using registered herbicides.
  • Cut-stump application using a registered herbicide is also described as a treatment option.

Hygiene and washdown

  • Seeds can be carried as contaminants on machinery, so clean machinery before moving it from infested 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): National priority exotic pest. On the National Priority List of Exotic Environmental Pests, Weeds and Diseases, so any new detection should be reported straight away.
  • Queensland: Prohibited matter. Report it to Biosecurity Queensland on 13 25 23 within 24 hours and do not move or deal with it. 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: Not declared. Not declared under the Landscape South Australia Act 2019. Other laws may still apply.
  • Western Australia: Not listed. Not found in the Western Australian Organism List. Check with DPIRD before moving or keeping it.
  • Tasmania: Not declared. Not a declared weed in Tasmania. Other laws may still apply.
  • Northern Territory: Declared weed. Weeds Australia lists it as a declared weed in the NT under the Weeds Management Act 2001. Check the NT declared weeds list for its class and what it requires.
  • 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.

Sources