Tests have confirmed the bacterial disease PSA is present on three kiwifruit orchards in the Te Puke area, says Agriculture and Biosecurity Minister David Carter.
The Ministry of Agriculture and Forestry has placed another two orchards in quarantine pending the outcome of a positive identification.
On Wednesday Mr Carter and the ministry's head of biosecurity held a series of meetings with Bay of Plenty growers to discuss the implications of the disease.
He says ministry staff are checking 20 orchards out of 75 where growers have identified possible symptoms of PSA on their vines.
On Thursday, the ministry will organise for growers with infected orchards to begin a copper-spraying programme in a bid to reduce the bacteria spreading.
Mr Carter says the ministry will still look at eradicating the disease once the extent of its spread is known.
Ministry trying to contact workers
Ministry biosecurity deputy director-general Barry O'Neil says it will be several days before the extent of the outbreak is known.
Urgent inquiries are being made to find contractors and beekeepers who have worked at kiwifruit orchards possibly contaminated.
The ministry says that if more cases are confirmed in the next few days it may look to contain the outbreak, but has admitted eradicating the disease may not be possible.
Dr O'Neil says information on people and equipment movements is being gathered rapidly.
"We are tracing forward any risk movements of those properties, identifying both the contractors and the beekeepers with respect to where the hives, or where the equipment that has been on these orchards has gone to.
"We will then be following up with the other orchardists that could be involved."
The ministry says the disease can be spread by wind, bees and poor agricultural hygiene.