Dave MacLean said an unchecked outbreak would be devastating. (CBC)

Forest scientists are warning a bug that first troubled New Brunswick forests for 40 years ago is on the brink of another outbreak.

A spruce budworm infestation could cost the province's forest industry more than $1 billion because the larvae eat the type of trees that make up more than half the province's woodlands.

The budworm population has been booming in Quebec for the past three years.

Entomologist Jeremy Gullison said last season's surveillance traps for budworm moths in Northwestern and Central New Brunswick showed the highest numbers in six years.

"The increase in the trap catches seems to be gaining momentum. I would say that there are pretty good indications that we're on the cusp of another outbreak," he said Wednesday.

Aerial bombardment

Over the four decades of the last outbreak, New Brunswick attacked the worm with bomber aircraft and chemicals.

At its height in 1975, the spray program against the spruce budworm covered more than half the province.

There is no call for a spray program this year, but it could be an inevitable choice.

Dave MacLean, a forestry professor at the University of New Brunswick, studied an uncontrolled budworm outbreak in Cape Breton, N.S., during the 1980s.

"It tends to typically take about four or five years before trees start to die, and then it really picks up," he said. "The mortality increases between the fifth year and the tenth year. Much of the trees are dead by then. At the same time, the stem growth is going down by about ninety per cent."

Mark Arsenault, president of the New Brunswick Forest Products Association, spoke to CBC News at the forest industry’s annual meeting Wednesday.

He said he is aware of a budworm threat.

"Hopefully, where we know that it's coming ... we actually might be able to have a very dramatic impact on the spread of it here in New Brunswick, because we'll have a preventative approach rather than a reactive approach," he said.

Minister waiting for advice

Natural Resources Minister Bruce Northrup said he will wait for developments and expert advice before acting.

"We definitely are prepared for it. We've done a lot of work in the past and it is in that cycle right now to be looked at. We're concerned about it but I have great confidence in my staff that they're monitoring it," he said.