The final cost of the PSA vine disease to the kiwifruit industry is now predicted to exceed $1 billion.
The bacteria was discovered on a Te Puke orchard in November 2009. Now nearly 1600 kiwifruit orchards have PSA and the number is growing.
It's not known exactly how the virulent strain of PSA got in, but it's likely to have come in on pollen imports.
Up to 700,000 shipping containers cross New Zealand's borders every year, along with 50 million mail items and five million passengers.
While all containers are checked for unwanted pests, the Ministry for Primary Industries says it's unrealistic to check every passenger.
More about protecting New Zealand from biosecurity threats can be heard in Insight on Sunday.