A deadly pest has continued its march south, prompting a plea for vigilance.

A nest of fire ants has been detected at Wardell, south of Ballina, the NSW Department of Primary Industries says.

A gardener raised the alarm on Friday after disturbing the nest and being bitten, suffering what’s described as blistering pain.

Authorities are due to examine the site on Saturday and destroy it with liquid insecticide.

The insects are a reddish-brown colour measuring two to six millimetres and can be aggressive when disturbed.

Tiny but tenacious, fire ants are a dire threat to animals, humans and agriculture. Photo: AAP

Invasive Species Council advocacy manager Reece Pianta said the spread to Wardell was a very alarming development.

“Everyone in the Northern Rivers should be out checking for fire ants, particularly if you have had any recent material delivered to your property like soil, turf or mulch,” he said.

He said the ants were one of the world’s worst super pests and could do more economic damage than cane toads, rabbits, feral cats and foxes combined if they were allowed to spread across Australia.

Mr Pianta called for eradication efforts to be increased and said these could not be allowed to fail.

Their nest flooded, these fire ants formed a raft and floated off to form a new colony.

The department is still working to establish how long the ants have been in Wardell and how they arrived.

They are known to travel in floodwaters by locking together to create rafts and are most active during wet weather, according to the Invasive Species Council.

The Northern Rivers area has been impacted by flooding recently.

The ants can be found in southeast Queensland and were first detected in NSW in November at a property 13 kilometres south of the border.

Fire ants are native to South America and arrived in Australia in the 1990s in freight.

The nation’s bid to eradicate the pest will be examined in a Senate inquiry.

Federal Agriculture Minister Murray Watt has previously said they could cause more damage to agriculture and the environment than all other invasive pests combined.

-AAP