THE fatal Tasmanian devil cancer has reached the marsupial's last great stronghold in the island's north-west, fuelling a dispute about the region's Tarkine wilderness.

A young male trapped by wildlife researchers in plantation forests near Burnie is believed to have contracted devil facial tumour disease, adding to two earlier confirmed cases in the same area.

The cancer has ravaged devils, threatening their extinction in the wild. Numbers have plunged by 84 per cent since the disease first took hold in the late 1990s, according to the Save the Tasmanian Devil Program.

Scientists have seen the disease steadily sweep from east to west across the island over the past decade, to affect devils in the island's north-west, where their numbers are still healthy.

Conservationist pressure is rising on the federal government to slow this incursion.