The Department of Agriculture has introduced a ban on importing ash plants and seed to combat ash dieback disease.
Minister of State Shane McEntee said the legal measures are being introduced in conjunction with similar moves in Northern Ireland to keep the island of Ireland free from the disease.
The co-ordinated move was taken to help prevent the spread of Chalara ash dieback, a disease of ash trees which is caused by the fungus Chalara fraxinea.
The measures will make it an offence to import ash plants and seed from areas within the EU that are known to have the disease.
Mr McEntee said the move "follows on from a voluntary import ban from continental Europe by the forest nurseries".
Minister for Agriculture Simon Coveney said any threat to Ireland’s forestry sector must be addressed decisively.
Northern Ireland Forestry Minister Michelle O'Neill said ash dieback represented a serious threat to native trees.
She said she welcomed the opportunity to co-operate within a "Fortress Ireland" approach to plant health.