The Department of Agriculture has issued an alert to the public to be on the look out for the oak processionary moth tree pest.

The first nest of caterpillars in Ireland was identified in June after it was spotted on an oak tree by a member of the public in a small park in south Dublin.

The department said that after the single nest was identified through contact with its Horticulture and Plant Health Division, "swift action was taken to eradicate the pest traced to a recent import of oak trees from Belgium".

It said this included "the removal and destruction of the single nest found on the solitary tree as well as all associated trees linked to the imported consignment".

A wider intensified survey has not yielded any additional findings of the pest in Ireland.

Information posters have been put in the park to alert the public and a trader notice has been issued to the horticulture industry.

Speaking to RTÉ's News at One, Declan Kealy, a spokesperson from the Department of Agriculture, Food and the Marine, said that the caterpillar can cause a nasty rash and irritate the eyes and throat.

He urged the public not to touch any sightings of the caterpillar.

Mr Kealy said the black and white caterpillars are hairy and are very evident moving in a 'head-to-toe-style' procession on a tree.

The concern is the caterpillars will turn into moths and invade other trees.

The single nest of caterpillars was found in June (Pic: Dept of Agriculture)

The pest is established in central and southern Europe and surrounding areas and the range of this moth has expanded northwards possibly in response to climate change, according to the Department of Agriculture.

It is firmly established in northern France and the Netherlands and has been reported in southern Sweden.

Since 2006, colonies of larvae have been found in parts of the UK. This is the first finding in Ireland.

Ireland is designated a Protected Zone since 2014, which means it is free from the pest. Northern Ireland and most of Britain also have Protected Zone status.

Measures are taken like prohibition or restriction of movement of commodities and annual surveys to avoid the introduction of these pests into the protected zones and to ensure their eradication if found present in these zones.

Oak trees and plants are a host for this pest and it is unlikely to be found on any other tree than oak.

The nest was removed by Department of Agriculture staff (pic: Dept of Agriculture)

The caterpillars have black heads and bodies covered in long white hairs, and have a distinctive habit of moving in nose-to-tail processions, hence their name.

When the caterpillars develop into moths, they then then fly into other host oak trees and lay their eggs for the next year.

The Department of Agriculture said they should not be touched under any circumstances and suspected sightings should be notified immediately to them by using the tree check app or by emailing plantandpests@agriculture.gov.ie.