Ministry for Primary Industries officials have approved an incursion programme in mid-Canterbury following a spillage of one of Europe's most invasive arable weeds - black grass - found in a consignment of imported fescue seed.
When the contamination was identified, the seed was securely contained and transported importers, PGG Wrightson'sfacility in Tinwald.
At the end of June it was shipped in unsecured seed boxes to a seed dressing plant on Cainbrae Road, near Methven. About 30 kilograms of the seed, containing an estimated "egg cup" full of black grass seed, blew out en route.
Because the shipment of seed from Denmark comprised of several sources, it cannot be ascertained whether the black grass which landed in Mid Canterbury came from spray resistant stock.
The incursion response will involve spraying the roadside with selective herbicides at least three times a year combined with an intensive surveillance programme.
"The spraying programme will be a scattergun approach, using chemicals that we hope will get on top of it and blitz it," Federated Farmers Mid Canterbury grain chairman David Clark said.
"Eight or nine times each year rogueing will be carried out."
This will involve workers physically working the roadsides digging up the noxious plant.
However, Mr Clark said that during the six-week delay in informing farmers, herds of cows had been driven up the contaminated roadsides.
"They will have trampled the seed in or carried it into paddocks," he said.
To compound matters soil was stripped off the roadside berm and carted away during road works.
Federated Farmers and the Foundation for Arable Research (FAR) are in the process of formally notifying farmers in the incursion area. Affected farmers will also be asked to audit the movement of livestock and attempts are underway to trace the soil removed by contractors during the roadwork.
Mr Clark said the surveillance programme would also have to take in water course which ran alongside or cross the affect roads, and any shelterbelts or trees in the vicinity.
