The horticulture industry is seeking an urgent meeting with the Tánaiste, Ms Harney, to discuss her moves to limit work permits for non-EU workers.
An estimated 4,000 to 5,000 workers, mainly from former Eastern-bloc countries, are employed in the industry.
Limiting entry to them would have "serious consquences" for Irish horticulture, Mr John Coleman, chairman of the Irish Farmers Association's Horticulture Committee, said at the weekend.
He said there had been a dramatic change in the economy here over recent years and the horticulture industry was now "firmly dependent" on non-European economic area (non-EEA) workers.
"The days of horticultural producers being able to source Irish workers ended with the rise of the Celtic Tiger, and this in not about to change," he said.
"While unemployment is increasing in this country, it would take an economic collapse before horticultural producers would have any hope of sourcing Irish and EEA labour," he added.
He said the Government had to be practical on this issue and realise the serious consequences of any move to limit the availability of work permits.
Most of the workers who come into this country to work in fruit- picking, and mushroom, root crop and vegetable harvesting are from Poland, Latvia, Estonia and Ukraine.
The Irish meat industry is heavily dependent on workers from Brazil and other Latin American countries.