Pest plant species: Alligator Weed

Alligator weed or Alternanthera philoxeroides is one of the world’s worst pest plants. Originating from South America, it has the ability to dramatically alter wetlands, small lakes, rivers, dams and drains. It can also take up heavy metals from the soil, is known to be toxic to some livestock and can block access to waterways for recreation.

Alligator weed can spread by water movement such as floods or tides, eel nets and boats. It spreads on land from soil movement, and equipment such as diggers and farm machinery. When disturbed, the weed breaks up into small fragments and when those fragments are transported to new sites, it regrows very quickly.

Alligator weed in our region

We need your help locating alligator weed in the Mangaone Stream and the lower Manawatū catchment. This area includes the stream area north of Colyton through Palmerston North to the Manawatū River, and down to Foxton Beach.

The weed was first spotted in Palmerston North during Alert Level 4 in late March 2020. The only previously known location of the weed in the Horizons Region was the Taumarunui effluent ponds, which makes this new find very concerning.

Horizons urges communities to help eradicate this pest from our region by reporting any sightings to the pest plant team by calling freephone 0508 800 800, email, or social media.

Alligator weed management in the Mangaone Stream

Last 2 years of management works are displayed below. Contact us to request all data (dates back to 2020).