The disease of ash trees which is caused by the fungus Chalara fraxinea, was identified in young ash saplings at five sites in counties Down and Antrim.
The plants, all linked to continental imports, showed symptoms of the disease and after samples were sent for laboratory analysis results proved positive.
Statutory notices has been served on the owners of the plantations requiring destruction of around 5,000 affected ash saplings and associated plant debris. The department is also investigating a number or other sites planted with imported ash saplings as part of its ongoing surveillance programme.
Outlining the situation, Minister for Agricultural and Rural Development Michelle O'Neill said: "During a survey initiated last month by DARD and subsequent laboratory analysis, the disease has been found in young ash saplings at five different sites. This is the first time the disease has been confirmed in the north.
"My officials have been working with the plantation owners and statutory notices for the destruction of ash saplings and associated plant debris has been served. The saplings and debris will be destroyed by burning and this work has already commenced. We have alerted our colleagues in the south and are continuing to work closely with them."
The Minister explained that all actions to contain and eradicate the disease have been taken by the Department, in line with scientific and legal advice. She added: "Legislation was introduced north and south last month banning the import and movement of ash plants for planting from infected areas. However, we must remain vigilant as this disease still poses a very serious threat. I would appeal for a responsible approach over the coming season. I encourage all stakeholders to be alert for signs of this disease and report findings."
The disease has already been found in parts of Scotland and England.
Further information on the disease and reporting finding is available on the Department's website at the following link http://www.dardni.gov.uk/ash-dieback.