Backpacker visa cuts may be ushered in without calculating the effect on harvests, with fears Australia's produce will rot on the ground without key seasonal workers.
The federal agriculture department was consulted on changes to working holiday maker visas, but there has been no modelling on how the reforms will impact harvest volumes, a Senate estimates hearing was told.
"We haven't done any modelling and we ordinarily wouldn't ... on a matter that is led by another agency," deputy secretary Matt Lowe told the hearing in Canberra on Tuesday.
Limited workforce data from the horticulture sector was a central challenge in modelling, Mr Lowe said.
Greens Senator Vanessa Bleyer asked whether the visa cuts could be compared to workforce shortages during the height of the COVID-19 pandemic, when produce was "rotting in the ground".
The NT government has said the changes would leave the Top End mango harvest without 1000 workers and 70 per cent of the crop would be left to rot on trees.
The WA premier has also written to the federal government, expressing concern about how the changes will effect the state's remote communities and its tourism and hospitality sectors.
Home Affairs Minister Tony Burke announced changes to be rolled out over the next year, reducing the cap on second-year visas from 57,000 to 45,000 and cutting third-year visas from 31,000 to 5000.
Backpackers will enter a ballot for the chance to remain in Australia for more than a year, meaning there will be about 38,000 fewer second and third-year backpackers than in 2026.
Labor Senator Anthony Chisholm said the COVID-19 comparison was not fair, with the government's projections still sitting above pre-pandemic levels.
The Pacific Australia Labour Mobility (PALM) scheme, which allows businesses to hire workers from Pacific countries and Timor-Leste, successfully boosted the sector, Senator Chisholm said.
"We are in ongoing discussion with Minister Burke's office, and so is industry, about how these changes are implemented to ensure we can manage this as best as possible," he told the hearing.
The National Farmers Federation has called on the government to revert to regular visa processing, with the PALM scheme not suitable for every business.
"Backpackers provide a mobile workforce for short and intensive seasonal windows," president Hamish McIntyre said in early October.
"Farmers cannot be told simply to switch programs when those programs have different purposes, requirements and operating models."
The coalition has promised to scrap the caps on working holiday maker visas, but fees would be increased for those looking to stay longer than one year in Australia.
Exemptions would apply for those who carry out work in regional areas.