Up to 50 plant nurseries across the country must follow new hygiene and management rules as the government tries to contain the spread of myrtle rust.
A biosecurity operation is in place in Kerikeri, where two properties have been found with the fungus which can kill pōhutukawa, feijoa and rata.
The Ministry for Primary Industries has now set out legal controls on plant nurseries requiring them to follow hygiene, containment and management protocols.
The controls are mandatory for all plant producers and retailers in Kerikeri, as well as those who have received myrtle plants from the area.
Ministry spokesperson Geoff Gwyn said the new rules should not significantly change the way they did business and would allow them to stay open.
Mr Gwyn said nurseries had already supported the response by following the protocols voluntarily since the third day of the operation.
While all other suspected finds that had been sampled had tested negative for myrtle rust, Mr Gwyn said there was still no room for complacency.
"We are still in full response to this situation and working to locate any other potential areas of infection out there."