The Ministry for Primary Industries is planning to tighten the rules on tomato seed imports.
The changes are designed to prevent five specific diseases from entering the country.
The ministry says under the revised import health standard, exporters would have to certify that the seeds were free of the five viruses and viroids.
And seed that had been personally collected or purchased from non-commercial sources would no longer be allowed into the country.
MPI says an incursion of one of the targeted diseases could infect a number of horticultural crops, including tomatoes and potatoes.
Public submissions on the proposal are open until 20 July.
The ministry says the changes are part of a broader programme to protect New Zealand.
Last week an independent review on biosecurity measures in force at the time the PSA kiwifruit vine disease entered the country, found significant shortcomings in four areas, including inadequate import controls on kiwifruit pollen.