Canterbury Regional Council will be taking to the air soon as it tries a new approach to controlling one of the most challenging plant pests confronting farmers.
Chilean needle grass has infested almost 300 hectares of land on nine properties in Canterbury since first identified near Cheviot in 2008.
The South American weed has also invaded thousands of hectares of land in Marlborough and Hawke's Bay.
The Environmental Protection Agency has approved the use of a more effective herbicide, Taskforce, for controlling the weed and has now cleared it for aerial spraying as well.
Environment Canterbury principal biosecurity advisor Laurence Smith says aerial spraying is necessary because some of the infested areas are in steep hill country.
He says the herbicide can't be used in wet conditions, so the council is waiting for drier weather to start spraying in North Canterbury.
Mr Smith says a helicopter will spray Taskforce on three properties in Hurunui District.
The most substantial area is between Cheviot and Waiau where more than 100 hectares will be treated.
Mr Smith says Chilean needle grass has gained a hold in some waste areas at a vineyard at Spotswood which will be sprayed, and Taskforce will also be applied to an area of about eight hectares in the Leamington Valley.
Mr Smith says Chilean needle grass is closely related to another serious plant pest, Nassella tussock, and is a threat to sheep farming because its sharp, needle-like seed head causes wool, meat and pelt damage and animal welfare issues.