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Small-seeded alfalfa dodder (Cuscuta planiflora)

This introduced parasitic plant is recorded in Victoria, Western Australia and South Australia. It attaches to other plants for nourishment, including legumes and some native herbs, and can affect the plants and vegetation it infests.

Key facts

Type: Weed, vine and creeper.

Native to: Europe and the Mediterranean.

Established in: VIC, SA, WA.

Other names: Small-seeded dodder.

Best time to act: Search for it in spring and summer, and treat infestations before flowers develop into seed capsules.

Identification

  • Look for reddish, fine, leafless or nearly leafless stems twining around host plants.
  • Flowers grow in compact clusters in leaf axils, usually 2–6 mm across, with a small blunt bract beneath each cluster.
  • The tiny flowers are white or pinkish, with five parts, and are mainly present in spring and summer.
  • Flowers are about 1.5–2 mm long; the unequal, broad-triangular calyx lobes are about 1.3–1.7 mm long.
  • The subglobose capsules are about 1–1.5 mm across and split around the middle; seeds are up to about 1 mm long.
  • Look-alike: Other dodders (Cuscuta species) also have fine twining stems and can be difficult to distinguish; seek expert identification when the species is uncertain.

Where it grows

In Victoria it is known from a few localities west of Melbourne, where it grows on host plants, often leguminous herbs, and has also been recorded in Western Australia and South Australia.

Why it matters

  • It is parasitic, attaching to host plants and drawing nourishment from them, which can weaken affected plants.
  • Recorded hosts in Victoria include leguminous herbs as well as Frankenia pauciflora, Lobelia pratioides, Selliera radicans and Wilsonia backhousei.
  • Infestations can affect native herbs as well as other host vegetation.

How it spreads

  • Seeds can be moved in contaminated soil or plant material.
  • Avoid moving potentially contaminated fodder, machinery or equipment between sites, as these may carry seeds.

Control options

  • Remove or cut out infested host plants and dodder before capsules mature, taking care to collect all plant material.
  • Contain removed material and dispose of it through an approved pathway; do not spread it or place it in ordinary compost.
  • Use herbicides only where a product is registered or otherwise permitted for the target and site, and follow its label and local authority advice.
  • Recheck treated sites and nearby host plants over subsequent seasons, and contact the relevant state biosecurity agency for advice on suspected new infestations.

Hygiene and washdown

  • Before leaving an infested site, clean soil and plant material from boots, tools, vehicles and machinery, and contain the debris for appropriate disposal.
  • Do not transport potentially contaminated soil, fodder or plant material to clean sites.
  • 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: Permitted, not declared. Listed as a permitted organism in WA, so it can be brought in, but it is not a declared pest.
  • Tasmania: Declared weed. Property managers are required by law to control declared weeds, and their import and sale are prohibited.
  • 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
  • Western Australia: Biosecurity and Agriculture Management Act 2007 (WA), administered by the WA Department of Primary Industries and Regional Development

Sources