The agency has been investigating the appearance of this pest weed on a small number of South Island properties and has been steadily building a picture of where the weed is present and if there are any common factors between affected properties.

Plants and Environment Surveillance Manager, Mark Bullians, says MPI has now positively identified velvetleaf on ten properties across the South Island and has seven further suspected cases yet to be verified. "The common denominator is fodder beet crops and, in particular, crops grown from two varieties of imported fodder beet seed.

"Velvetleaf plants are appearing in rows where this fodder beet seed has been drilled and farms concerned have planted either Kyros and/or Bangor seed. While we are not certain this is the full picture, we now know that some lines of these two seed varieties are very likely to have been contaminated with velvetleaf seed. For this reason, we urge anyone who has planted Kyros and Bangor fodder beet seed to check their fields immediately for the presence of velvetleaf. The seed has been distributed mostly in the South Island but some has been sold in the North Island.

"If you believe you have found this distinctive weed, call MPI immediately on 0800 80 99 66."

Velvetleaf is a tall-growing weed reaching heights of up to 2 metres. It has buttery yellow flowers and large velvety heart shaped leaves.

Bullians says farmers are advised to photograph any plants, contact MPI and mark the location of plants so they can be found again easily. He cautions against pulling up plants, or allowing cattle to graze infested crops, and says an MPI or local council representative will visit and carefully remove any plants to make sure velvetleaf seed, if present, is not spread.

Velvetleaf is a serious weed pest overseas, damaging crops by competing with them for nutrients and water. It is an Unwanted Organism under the Biosecurity Act, and as such, entry to New Zealand is prohibited.

MPI is investigating how the weed seeds could have entered New Zealand. The affected consignments met New Zealand's importing requirements and were certified as weed-free by the exporting country. The Ministry is currently reviewing the import requirements for seed.

Bullians says the Ministry is working closely with primary industry bodies from both the animal and grain/seed sectors as well as regional councils on managing this situation. As a precautionary measure, MPI says it has directed seed and grain retailers not sell or distribute any remaining stock of the affected seed lines and these retailers have also been directed to instruct buyers to return any unsown seed.