Trees and other vegetation in Sherbrooke Forest in the Dandenongs have had to be fenced off to protect them from repeated damage from wild deer.

Sassafras trees, after which the picturesque Dandenongs village was named, are being rubbed by wild deer and effectively "ring-barked", environmentalists have warned.

Environmental scientist Alex Maisey, convenor of the Sherbrooke Lyrebird Survey Group, said rubbing by deer could kill tree bark and eventually lead to trees rotting at the base and falling over.

Deer had caused significant damage in and around Sherbrooke waterways as they trampled through them and created "dozens of deer wallows" as they rolled around on the ground and in creek beds.

The deer were a "very significant" problem in Sherbrooke "with large amounts of erosion still occurring on the creek banks … they're still very active," he said.

A shooting program coordinated by Parks Victoria that commenced in 2014 had reduced the deer damage, particularly in its first 18 months, he said. But over recent months, including over summer when shooting stopped, the damage had picked up again.

"I would say there's clearly a lot more deer in the landscape than what was originally thought. There's also a lot surrounding Sherbrooke that are coming in from elsewhere," he said.

Mr Maisey said the deer population in the Dandenongs surged in the aftermath of the Black Saturday fires. "There seemed to be a huge explosion throughout Victoria and I think that led to even more animals coming into Sherbrooke," he said.

"They really target those Sassafras, the dominant tree in the threatened rainforest vegetation community ... It might be because it's aromatic, or the texture of the bark," he said.

Deer photographed by remote camera in Sherbrooke Forest in 2013. Photo: Supplied

Under a grant valued at almost $50,000 environmentalists are fencing off 15 plots that include trees and other vegetation. A further 25 Sassafras trees will be protected via tree guards.

Local environmental volunteer and retired forester Bill Incoll said wild deer were one of the biggest environmental problems affecting Sherbrooke Forest.

Asked about the shooting program in the Dandenongs, he said: "It just needs to be a program that's long-term ... the other thing that's necessary is it be extended to areas where there is as yet, not a huge problem, because there are deer throughout the Dandenongs and their population will increase."

Craig Bray, Parks Victoria district manager for Dandenong Ranges and Yarra Ranges, said the deer shooting program in the Dandenongs had been successful. "Environmentally we are seeing improvements in habitats," he said.

"I've always said that they are a transient species. They can travel long distances. Effectively it'll be a program that will need to run based on the evidence we have around the impact on vegetation and habitat," he said.

Shooting is occurring at three locations in the wider district, at Sherbrooke, the Yellingbo Nature Conservation Reserve and Warramate Hills Nature Conservation Reserve. Twenty deer had been shot in in the parks this year and 185 since it started, he said.

Mr Bray said Parks Victoria was "very happy" to support the program under which vegetation plots and trees were being protected.