The first rounds of official surveillance in Mid-Canterbury have turned up no signs of black grass - seeds of which spilled in the region following a biosecurity botch-up in July.
Black grass is notorious in Europe where it's highly resistant to herbicide, spreads rapidly and reduces the yields of wheat, rapeseed, forage legumes and barley.
It got into the country in a shipment of red fescue seeds imported by PGG Wrightson for use on turf.
The Ministry for Primary Industries detected the black grass seeds at the border, but allowed PGG Wrightson to transport to a sorting warehouse.
However, the company didn't secure the load and spilled the seeds along State Highway 77 in mid-Canterbury.
Ministry response manager David Yard says so far there's been no sign of the grass, but the surveillance programme is just beginning.
He says there have been three rounds of intensive surveillance along the the route were seed was spilled and to date there is no evidence of back grass seeds.
Mr Yard says a further six rounds of surveillance are scheduled for this year and the programme will run for a further 2 years.
He says it's likely a small number of the black grass seeds could germinate.
And he says the accusation made by the Public Service Association that the biosecurity incursion was the result of staff cuts caused by the government's restructuring, doesn't add up.
"I'd like to say that the spillage was in no means attributable to any reduction in staff. The spillage occurred as a result of failure to comply with requirements by industry themselves.
He says in fact quarantine inspectors are to be credited for picking up the contamination because the original consignment was labelled incorrectly as being free from contamination.