A Ministry of Agriculture and Forestry report shows Psa is having a severe impact on the premium Gold kiwifruit variety with production forecast to be well down in 2012.

The half-yearly report shows loss of vines since the virulent strain stuck in November 2010 could take production of Gold kiwifruit from 30 million trays in 2011 to 20 million or even 10 million trays in the 2012 season.

Red ooze on a vine is a spring symptom of the Psa infection.

Psa has hit hardest around Te Puke in the Bay of Plenty where 41 per cent of the total planted area is located.

At this stage, just over one quarter of kiwifruit orchards in New Zealand are known to have the bacterium present.

Overall, up to 20 per cent of Gold kiwifruit in Te Puke could still be harvested, and up to 80 per cent could be in the wider Bay of Plenty.

This would yield an export volume of about 16 million trays of Gold kiwifruit.

Psa has been slower to affect Green kiwifruit orchards, but orchard infection numbers have ramped up during the 2011 spring.

The report says the impact of Psa on Green orchards in the medium term remains uncertain.

Overall, export volumes are expected to fall 21 per cent to 89 million trays, and export returns are expected to fall 18 per cent to $862 million for the year ending 31 March 2013.