They're inventorying trees at Mount Rushmore National Memorial, with an eye out for trees that are infested with mountain pine beetles.
Those tiny insects can lay waste to lodgepole forests if they gain enough of a foothold by boring into the trees' trunks and killing them. Earlier this year officials at the memorial began working on a plan to combat the beetles, and the first on-the-ground step is inventorying the forests on the grounds to gauge beetle infestations. That work started Friday.
These trees are currently hosting the newest generation of pine beetles and have been killed by the beetles. Pine beetles in green infested trees typically leave the trees in July and August to find new host trees. With the help of South Dakota State University and the South Dakota Cooperative Extension Master Gardeners, Mount Rushmore will be surveying the forest to identify and mark green infested trees. Once these trees have been identified, they will be cut down and dried out to remove and kill the immediate pine beetle population that is in the park. This process will be done every year to identify any new beetle infestations.
The second phase of the plan will begin Tuesday to protect the large-diameter, high-value trees within the visitor areas. High-value trees have been identified as trees larger than 10 inches in diameter and ones that contribute to the forested views of the memorial. If these trees were gone, visitor views of the memorial would look very different. The trees will receive a preventative insecticide spray that will ensure the forested views of the memorial will remain intact.
Mount Rushmore has identified more than 700 trees to be sprayed during the month of June. Carbaryl 4L insecticide spray is the chosen spray for this project. It has proven success in the Black Hills and has also been used in Rocky Mountain National Park to combat the MPB. Trees will be sprayed on their trunks by spray units on the ground. While the spray is being applied to the trees, many visitor areas may be closed to the public.
Actions to ensure the health and safety of park visitors and staff include park closures to keep sprayed areas secure. Areas that have been sprayed will be closed to visitors and staff for approximately 3-5 hours while the carbaryl dries on the trees. Once the spray is dry, the area is safe to re-enter. Signs will be posted near the sprayed areas to identify trees that have been sprayed. Spraying is scheduled to occur in the early morning, with areas closed to the public until noon or 1 pm.
Areas will be sprayed in sections and include trees along the Presidential Trail, around the historic Sculptor’s Studio and along the roadways.
Memorial officials hope that these proactive and preventative measures will protect the park’s forest from the worst damage caused by the current MPB epidemic. The most active area of MPB infestation and highest concentration of tree mortality is in close proximity to the memorial and the oncoming infestation has recently been observed within the park as well.
The current outbreak appears to be larger and more widespread than historically typical. Mount Rushmore’s MPB Assessment and Action Plan was developed to address the current epidemic and identify actions that officials hope will return the forest to a more historic and sustainable condition that can naturally protect itself against future pine beetle infestations.