Federated Farmers is worried about the potential impact of black grass on the country's seed production industry.

Seeds from the invasive weed have been found during a routine sampling in Canterbury, and the Ministry for Primary Industries is trying to find the source.

Federated Farmers spokesman Guy Wigley said New Zealand is a world leader in seed production, and the business earns good export revenues. 

"It's a priority one incursion, so MPI are putting full resources into making sure it's contained."