Tomato growers fear the "foot and mouth of horticulture" will enter New Zealand because of more imports from Australia.
Growers have raised concerns about a proposal before the Ministry of Agriculture to allow imports of four more varieties of Australian tomatoes.
They believe the imports could bring in exotic fruit flies -
a problem in some of Australia's main tomato-growing regions.
But MAF says the extra varieties should make no difference to the biosecurity risk.
"We believe the system is such that any likelihood of Queensland fruit fly getting established in New Zealand through imported tomatoes is approaching zero," said Richard Ivess, director of plants biosecurity.
Commercial-standard fruit from Australian properties was chemically treated post-harvest for fruit fly larvae and eggs, he said.
The issue has arisen while New Zealand and Australia are still involved in the long-running row over apples.
Agriculture Minister Jim Sutton has criticised Australia's latest move to examine apples from New Zealand as a delaying tactic.
Quarantine authority Biosecurity Australia said it would set up a committee of experts to analyse import risks and review all information used in a draft report.
- NZPA
