Help needed for alpine mass murder mystery

Researchers want punters to help solve a murder mystery in the Australian Alps.

A mass snow gum die-off high in the hills has conservationists scratching their heads.

Matthew Brookhouse from the Australian National University has launched an online survey for people to report trees dropping dead.

"We have a small number of suspects," Dr Brookhouse said on Thursday.

"But we don't necessarily have the why."

The prime suspect is a type of wood-boring beetle.

But Dr Brookhouse isn't sure of exactly what bug to blame.

Researchers know these beetles fed on trees under drought stress.

The bugs carve big, two to four centimetre-wide incisions into affected snow gums.

But this could take months, even years, to show on the tree.

This means when people walked through snow gums, they could already be walking through a forest of zombie trees.

Researchers are unsure if drought conditions are creating more trees to feed on, or there is a sudden spike in beetle numbers.

"That's what we really need to get down to," Dr Brookhouse said.

He said if drought conditions exacerbated by climate change were to blame, then Australia's snow gums were in trouble.

The outbreak spreads south from the ACT to the Victorian border, affecting trees above 1600 metres from sea level.

Dr Brookhouse said a major die-off would have massive implications for Australia's alpine environment.