Copper-spraying has begun on one of the Bay of Plenty orchards worst affected by the vine disease PSA.
Three Te Puke sites have been confirmed as having the bacteria, one has returned a negative result and another is still awaiting test results.
A further 20 orchards in the Bay of Plenty are being tested by Ministry of Agriculture and Forestry staff after showing symptoms of the disease.
Biosecurity Minister David Carter says all five orchards are within 10 kilometres of each other. Mr Carter says testing is continuing so that a more definitive picture can be built up about the spread of the disease.
International experts have assured the ministry that copper-spraying will not defoliate vines or harm the fruit.
On Thursday morning, 40 horticultural staff from the ministry and kiwifruit marketer Zespri began investigating orchards in all of New Zealand's kiwifruit-growing regions for signs of PSA. The inspections will take place over the next two days.
More than 78 other suspected infections have been reported in orchards nationwide.
Property owners in the Bay of Plenty, Kerikeri, Gisborne, Hawke's Bay and Nelson have asked ministry staff to inspect spots and lesions on leaves.
Mr Carter says he will have a better idea of how far the bacteria has spread and how long it has been present by late Friday afternoon. He says he will then know the best way to proceed.
Mr Carter says the discovery of the disease is a huge wake-up call for all New Zealanders about the importance of biosecurity.
Ministry biosecurity head Barry O'Neil says it had intended to start copper-spraying on Thursday morning, but there were concerns such action would defoliate the vines. Dr O'Neill says overseas experts have confirmed the spray is fit for use on the hardest-hit orchard.
The bacteria could threaten New Zealand's $1.4 billion kiwifruit industry. Already the United States and Australia have banned imports of nursery plants and cuttings.
The disease can be spread by wind, bees and poor agricultural hygiene and appears as brown spots on leaves. Testing has begun to determine what strain has infected the plants, but results are not expected until next week.
Random leaf samples are to be collected from green and gold kiwifruit orchards in the Te Puke region to learn more about the geographical spread of the disease.
Orchard specialists will work with horticultural contractors to assess at least 40 orchards and collect samples of leaves, to be tested at the ministry laboratories.
Growers have also been asked to inspect their own vines and report their findings to kiwifruit marketer Zespri.
The ministry is describing its actions as a rapid response to the problem, although some growers believe faster action should be taken to destroy three confirmed infections.
The disease has been successfully controlled on kiwifruit plants in Japan, but a different strain has badly affected some crops in Italy.
No signs of disease in Nelson yet
The country's southern-most kiwifruit orchards in Nelson have found no signs of the bacterial disease so far.
Mainland Kiwifruit Growers chairman Rod Fry says checks of 140 orchard areas have found some spotted leaves, but there is no suspicion that it is PSA.
However, experts will be doing further checks in the next day or two.
Local growers are taking all possible precautions to prevent the disease, including banning the use of North Island pollen, he says.
Nelson produces about 5% of New Zealand's kiwifruit crop.