MAF's Psa spokesperson Doug Lush says the ministry is exploring the possibility the infection was introduced into New Zealand on imported plant material before the start of biosecurity testing.

Psa infected leaves being destroyed in the Pyes Pa area.

According to the Ministry of Agriculture and Forestry's plant import department, imported kiwifruit plant material has undergone some level of testing for decades.

It is not known exactly when MAF first started testing kiwifruit plant imports.

Doug says kiwifruit is not native to New Zealand and has been regularly imported over the years.

'Border provisions at the moment are very strict, but historically kiwifruit testing at the border has not been as great so it's possible it was brought in a long time ago and has been here in a dormant state.”

He says historical plant imports are just one of the many options MAF is investigating.

'A large number of ideas are being explored, but at the moment we have no idea how it might have gotten in.”

Zespri says 61 orchards are now confirmed with Psa, up from 55.

There are two new infected orchards in the Hawke's Bay, three in Te Puke and one in the Whakatane/ Edgecumbe area.

About one third of the infected orchards are Green variety growers.

Zespri has received 1239 emails through its Grower Contact Centre with about 44 per cent reporting suspected symptoms and 56 per cent emailing to report that their orchard is clear of Psa symptoms.