The claimants said effects of Psa on the kiwifruit industry were widespread and devastating to many growers and their families.
"Some of the kiwifruit growers were completely wiped out, facing virtually no crops for three years and plummeting values on their orchards," they said in a statement.
"They lost their businesses and were forced to sell their orchards at heavily discounted prices. Other growers that were able to survive the outbreak, suffered almost complete loss of income for several years and took on huge debt to replant their crops."
In 2004, MPI had identified that Psa was a risk to the NZ kiwifruit industry.
At the time, it undertook a full risk assessment and considered that imported kiwifruit bud wood and tissue culture "plant material" posed such a significant risk of carrying the Psa bacteria that they banned the importation of all kiwifruit plant material but they failed to consider whether kiwifruit pollen could carry Psa and didn't impose strict requirements on this, only requiring that a prior import licence be obtained.
In 2007, a pollen importer applied to MPI to import kiwifruit pollen. At this time, the claimants allege MPI failed to properly consider the specific risks that importing kiwifruit pollen posed to NZ, including whether kiwifruit pollen could carry the Psa bacteria.
MPI, in its statement of defence, said the "pathway" by which Psa entered New Zealand is not known.
"Possible pathways into New Zealand include smuggling of infected nursery stock; and the movement of people and contaminated equipment between orchards in New Zealand and infected countries," MPI said.
Once it had arrived, MPI said the disease spread widely through a range of pathways. Post incursion, some growers failed to adhere to proper hygiene standards, it said.
One of the claimants, Te Puke kiwifruit grower Alistair Reese, said some kiwifruit growers were long way off recovering from the outbreak.
"It really concerns me that a lot of the commentary about the kiwifruit industry is that Sun Gold (Gold 3) sas been the 'saviour' post Psa, and that the industry is now doing very well because of the new varieties.
"There's no doubt that the higher value kiwifruit gold variety has done well, but I think it's misleading to say that the whole industry has recovered - like myself, there are many kiwifruit growers who are still a long way from recovery seven years after Psa-V hit," he said in supplied comments.
Psa tore its way through what was then a popular gold variety - Hort16A - which turned out to be particularly susceptible to the disease.
MPI, in its statement of defence, said that it had, along with Zespri, put up $50 million for the purpose of managing the initial response, remediating losses, and providing payments to orchards.
In mid 2012, Zespri commercially released the new cultivar, Gold 3, which was Psa-tolerant. The licences were sold at a discount to affected growers on a one-for-one basis to replace Hort 16A.
MPI said Gold 3 has proven to be more productive than Hort16A, and had wide market appeal. Gold 3 licences have increased significantly since June 2012 and orchard prices have risen accordingly, it said.
As a result of the Psa incursion, growers have made significant improvements in orchard hygiene and management , which has led to an increase in crop yield, it said.
The case goes to the High Court in Wellington on August 7.