Farmers in the Horizons region are being asked to keep a close eye out for Chilean needle grass this summer.
The invasive pest plant is most easily identifiable in spring and early summer, when its reddish purple seed heads emerge.
Chilean needle grass infests 3700 hectares of land across Marlborough, Canterbury and Hawkes Bay. Nationally up to 15 million hectares are climatically suitable for its growth.
Horizons Regional Council Biosecurity Officer Jack Keast said the economic impacts could be devastating if Chilean needle grass were allowed to spread into the Horizons region.
The seed's sharp tip and twisting awn (bristle) can drill through animals' pelts and lambs' eyes, causing suffering and potential downgrading of carcases.