Zespri says removing infected plant material from orchards with PSA is now a matter of urgency.
The vine disease has now been confirmed in the South Island on two orchards in Motueka and Golden Bay, taking the total number of infected properties around the country to 28.
PSA was first spotted in Bay of Plenty and reported on 5 November.
Zespri chief executive Lain Jager says the number of cases of the disease found in orchards is rising daily and the industry needs to stop its spread now.
A growing number of orchardists say they have seen similar symptoms to those of the disease before.
Mainland Kiwifruit Growers chairman Rod Fry says the symptoms usually follow a wet spring and do not cause vine deaths.
He says the disease has previously caused spotting on leaves but no vine deaths.
Kiwifruit Growers Incorporated president Peter Ombler told Morning Report it is unclear how long PSA has been there.
Old samples to be retested
Scientists will re-test old kiwifruit samples using new molecular techniques to see if PSA has been present in New Zealand orchards previously and gone undetected.
Landcare Research says it's found no positive identification of PSA in its library of fungal bacteria, but the Crown research institute will retest samples kept frozen in liquid nitrogen.
Landcare, MAF and Plant & Food Research all have kiwifruit samples that can be re-tested. New DNA testing methods will be used.
Landcare team leader Dr Peter Buchanan says DNA sequencing technologies are able to identify PSA where previously it may not have been recognised.
Grower meetings
Zespri has organised a series of urgent meetings with growers to discuss the implications of PSA.
It will hold three grower meetings on Thursday in Te Puke, Tauranga and Katikati, and one in Kerikeri.
There will be a further meeting in Whangarei on Friday.
