Kiwifruit growers are seeking about half a billion dollars from the government over the PSA disease, in a Court of Appeal case starting today.
The growers won a big chunk of their claim for official culpability in the High Court last June, blaming lax biosecurity for the arrival of the vine killing disease in 2010.
The Crown denies it is liable however, and said the High Court got it wrong. Growers in turn filed two cross appeals, and all cases will be raised this morning.
The hearing is likely to be very complex.
PSA, or Pseudomonas syringae pv actinidiae, is a bacteria that can kill vines. It was unknown in New Zealand until 2010, and its arrival is estimated to have cost the industry close to $900 million.
That led a segment of growers, the 212-strong Kiwifruit Claim Group, to sue the Ministry for Primary Industries (MPI) for negligence in allowing PSA to enter the country.
They blamed a forerunner of MPI, the Ministry of Agriculture and Forestry, and sought compensation amounting to almost half those losses, $400 million.
The figure later grew to $450 million.
During hearings in 2017, Justice Mallon heard the growers' lawyers argue the disease came in a shipment of pollen products from the Chinese province of Shaanxi, which the Ministry of Agriculture and Forestry approved - something they said should not have been allowed.
MPI lawyers countered that it was unreasonable to punish officials for not stopping any and every incursion.
Furthermore, any liability on the Crown for losses as a result of a biosecurity incursion was covered by a statutory compensation scheme.
Justice Mallon found mainly for the growers, and said in her judgment the ministry owed a duty of care to kiwifruit growers.
She ruled it had responsibility for controlling goods that could be imported into New Zealand, and the risks of contamination should have been obvious.
Justice Mallon also found ministry personnel had not exercised reasonable care in preparing a research paper about pests and diseases associated with pollen.
She said the principal author and the supervisor of that paper had a different understanding of its scope, which meant relevant information was omitted.
However, the judge allowed that the ministry did not owe a duty of care to another plaintiff, the processing facilities of the Kiwifruit giant, Seeka.
She said post-harvest operators were one step removed from the direct harm suffered by growers, so were less closely connected to the consequences of ministerial negligence.
That and one other legal point form the basis of the growers' cross appeals.
In bringing in a restrained budget last year, Finance Minister Grant Robertson said he had to prepare for huge potential biosecurity costs.