An alien weed invasion is threatening Mid Canterbury's arable farming industry.

Officials are scrambling to deal with a roadside spill of seed contaminated with black grass between Ashburton and Methven.

Tiny seeds of a feared weed were spilled on the roadside in Mid-South Canterbury.

Black grass or meadow fox tail has established in winter crops in Britain and Europe.


The weed is resistant to many herbicides and is difficult to control in several crops. It competes for nutrients, light, water and space, out-competing crops and reducing yields.

Scientists from the Foundation for Arable Research, Primary Industries Ministry, Federated Farmers and E-Can staff intend to develop surveillance and eradication plans to deal with any areas of weed strike.

The contaminated seed lot has been isolated and returned to its country of origin.

According to FAR chief executive Nick Pyke only a small amount of seed was spilled and the percentage of black grass contamination was minimal.

"This considerably reduces the risk of this invasive weed establishing," Mr Pyke said.

"However, given its potential economic impacts, it is vital that all reasonable steps are taken to prevent establishment."

Black grass seed heads were usually reddish-purple, giving the appearance from a distance of black grass.

Germination of the spilled seed was most likely to occur from now through to April and any black grass would be most visible from November to April.