The Ministry for Primary Industries is encouraging mid-Canterbury farmers to mow their roadside verges following a biosecurity incident earlier this year where black grass seeds were spilt.
Black grass is highly resistant to herbicide and reduces the yields of many common crops overseas.
The pest seeds arrived in a shipment of imported fescue seed and while the ministry detected them at the border, PGG Wrightson subsequently spilt some seeds while transporting them to a secure facility for sorting.
Ministry response manager David Yard says the initial emphasis was on spraying and surveillance but the ministry now believes mowing can also play a critical role in stopping black grass becoming established.
"Because of our discussions with scientists in the UK where black grass is quite prevalent, one of the other important things that landowners can now do is to ensure that they regularly mow the grass in front of their property," he says.
The ministry has written to farmers encouraging them to mow roadside grass and, not remove the material.
That prevents the seedheads from developing and should reduce the risk of transmission, should the plant establish, Mr Yard says.
The ministry has carried out three rounds of surveillance since the July spillage and has not found any black grass. The surveillance programme will run for several years.