A bacterial vine disease discovered in 2010 has now infected about a third of New Zealand kiwifruit orchards, and will likely spread to all other orchards in the country, but 2012 exports to the U.S. may not be significantly affected.

According to Michele Hoard, senior marketing manager for Zespri Americas, a division of Mt. Maunganui, New Zealand-based Zespri International Ltd., the exclusive exporter of the country’s kiwifruit, 1,070 New Zealand kiwifruit orchards are now infected with the disease.

That represents almost a third of all orchards and just over 40% of all New Zealand kiwifruit acreage.

Of the infected orchards, 38% are green kiwifruit orchards, 51% gold orchards and the balance new varieties.

About 15% of New Zealand kiwifruit shipped to the U.S. are conventional golds, Hoard said. About 70% are greens and 15% organic greens and golds.

Green kiwifruit hasn’t been hit as hard by PSA as gold kiwifruit, Hoard said. New Zealand gold production is expected to be down 32% this season, but green production should be down just 10%.

Despite the high levels of infection, the effects on 2012 volumes to North America could be minimal, said Steve Woodyear-Smith, kiwifruit category director for Vancouver, British Columbia-based The Oppenheimer Group, Zespri’s North American marketing partner.

“Oppenheimer is looking forward to another solid New Zealand kiwifruit season, and anticipating similar volumes of green and gold fruit to 2011 levels,” he said.

The Zespri Gold, also known as Hort16A, the dominant gold kiwifruit variety licensed by Zespri, is highly susceptible to PSA.

“It is clear that in the future Hort16A in high-PSA environments is unsustainable,” Hoard said. “In the short term, those growers who can sustain a Hort16A crop will have very strong returns given the limited supply of gold fruit.”

A new gold variety, the Gold3, which is much more resistant to PSA, is expected to eventually replace much of the lost Zespri Gold acreage. By the 2015-2016 season, gold volumes are expected to return to their pre-PSA levels, Hoard said.