THE Department of Agriculture and Fisheries has finally fingered a prime suspect in the pasture dieback which has been gripping the North Burnett and much of Queensland the past few years.

But you would need a minuscule police height chart to take their mugshot.

Speaking at last week's Ag Network Forum at Mount Perry, senior extension officer Damien O'Sullivan said the department was narrowing in on a species of mealy bug which could be causing the carnage to pasture grasses.

"Mealy bugs are known for other diseases affecting grass plants,” Mr O'Sullivan said.

"They could have come from overseas.”

The working theory is that, although mealy bugs have been in Queensland for over a century, this particular species was transported from New Caledonia, which bore the brunt of dieback about a decade ago, by Cyclone Debbie in 2017.

Trials have begun at Brian Pastures Research Facility near Gayndah to determine whether any pasture grasses are resistant to the bug and also ways of combating it.

Meat and Livestock Australia has already invested $1million to diagnose the dieback.

"Work will be ongoing and there are no easy answers as yet,” Mr O'Sullivan said.

He said there were no current recommendations for combating the bug.

He suggested planting legumes or short-term crops in badly affected pastures.

Insecticides had anecdotal success but grazing animals would then ingest those chemicals, he said.

"If you'd asked me in July, I'd say there has been no progress, no idea what we're doing, but now we have lines of inquiry,” he said.