An invasive insect continues to ravage the mighty hemlock trees in the Great Smoky Mountains. The damage is so bad on Parson Branch Road, the risk of dead trees falling has made the scenic route too dangerous to drive.

"In terms of the hemlock wooly adelgid (HWA) and the damage it has caused, this is our first road closure due to the density of hazard trees in this condition. And it’s going to be a lengthy closure," said Dana Soehn, spokesperson for the Great Smoky Mountains National Park.

Signs at Cades Cove indicate the closure of Parson Branch Road.

The eight-mile road is a rustic one-way route accessed via Cades Cove and ends on U.S. 129.

Parson Branch Road is no stranger to closures. The route crosses streams 19 times and has experienced extensive flood damage in the past that caused it to close from 1994 to 1998 and again from 2003 to 2007. This time the danger was not created by the rising creek, but an insect with an insatiable appetite for hemlock trees.

The hemlock wooly adelgid gets its name from the small white wooly webs it forms at the base of needles on hemlock trees. The GSMNP has attempted to introduce predatory beetles and sprayed hemlocks to protect the trees from the insects, but the damage from an uninhibited invader has taken a huge toll.

"The hemlock wooly adelgid was first detected in the park in 2002. The park hasn’t experienced this kind of ecological challenge since the loss of the chestnut trees at the turn of the [20th] century.”

Bridge at Parson Branch Road in the Great Smoky Mountains.

Soehn said crews have been able to spray chemical treatments on around 15 percent of the hemlock trees in the park. The treatments clearly protect the hemlocks near headquarters where the needles are full of bright green growth and an abundance of cones.

But 85 percent of hemlocks are unable to be reached by crews and many have suffered a slow death. The towering trees on Parson Branch Road now stand as a collection of bare tombstones.

“There are more than 1,700 trees that are dead or dying within a tree’s-length of falling on the road. It was a shock for us to see this level of dead trees," said Soehn.

Removing the hazardous trees could cost up to $450,000. The GSMNP does not have that much money available in its budget, so the road has been shut down indefinitely to motor vehicles. The Smokies will request funding in 2017 to make repairs to Parson Branch Road, but that request could be denied with an already long list of projects with deferred funding.

Sun shines through the canopy of a healthy hemlock tree at Great Smoky Mountains headquarters.

In the meantime, Parson Branch Road will continue to serve essentially as a trail accessible to hikers, mountain bikers, and horses. However, park officials warn anyone using the road to do so at their own risk and with full awareness of the hazardous trees.

"People will need to always be on the lookout for falling trees in that area, especially on windy days or after periods of rain when the soil is soft," said Soehn.

For now the scenic treasure for cars that cruise slightly off the path of Cades Cove Is another casualty in the longtime war against a tiny invader.