Federated Farmers are calling for a ban on pollen imports and an end to artificial pollination of kiwifruit after the vine wasting Psa bacterium was found in both domestic and overseas pollen samples.

While the Ministry of Agriculture and Forestry (MAF) has said there is no scientific evidence the vine killing pathogen Pseudomonas syringae pv actinidiae (Psa) can be transmitted via pollen, growers have speculated the disease may have have arrived here in pollen imported from countries such as Japan and Chile.

Imported and domestic pollen is used in artificial pollination to increase yields of the fruit, but Federated Farmers' biosecurity spokesman John Hartnell said the practice should end immediately and imports be suspended until they were certified as free from of viruses and pathogens not already in this country.

Mr Hartnell said a freeze on artificial pollination was required not only to check the spread of the disease - which is expected to cost growers, the wider industry, and the Government up to $75 million over the next three years - but also to protect New Zealand's bees.

Federated Farmers' call comes after it was revealed in an industry bulletin from from Italy - where Psa ravaged up to 50 per cent of the kiwifruit crop two years ago - that New Zealand research suggested the disease could be spread by pollen.

MAF says the research has not been formalised, peer reviewed or published in a scientific sense and it is unwilling to base trade and importation policies "on a paragraph in a trade newsletter".

Meanwhile, the bacterium has also been found in locally sourced pollen this year and from 2009, suggesting the disease has been here more than a year.

Mr Hartnell asked "who in their right mind would continue to tempt fate" by continuing to use artificial pollination.

"On a more distressing note, who in their right mind would put at risk the New Zealand's bee industry? It is well recognised that more than 80 per cent of all pollination world-wide, including kiwifruit, is done by honeybees. To jeopardise this has massive implications."

Kiwifruit exporter Zespri yesterday said MAF was continuing research into how the disease spread and pollen was one possible culprit "It may be some time before we have a definitive cause of infection or spread and it is possible that this may never be fully identified," Zespri said.

Zespri also said four more orchards had tested positive for Psa, - one in the Te Puke region where it was first discovered and three in the South Island's Motueka region.