Fungus that kills red oak trees detected in Ann Arbor nature area
ANN ARBOR, Mich. (CBS DETROIT) - Several cases of oak wilt fungus have been confirmed in the Bird Hills Nature Area after a concerned resident reported a tree that looked unhealthy to city officials.
While it is common in Michigan, it's the first time the fungus has been detected in an Ann Arbor nature area.
Trees could be seen tagged at the site – candy cane striped tape for infected trees and pink tape for trees suspected to have the fungus.
"This candy cane stripe-tagged tree is the epicenter of the infection," said deputy manager of Ann Arbor's Nature Area Preservation Remy Long. "This tree is likely to have been infected for two and a half, three years."
The fungus spreads above and below ground through migrating beetles attracted to its scent and through root grafting between trees underground.
"If this went un-remediated, it could have spread through Bird Hills Nature Area within the next 10-15 years, truly devastating the red oak population within the park," said Long.
The city will have to remove 55 red oaks from the area, including one that is more than 200 years old.
Oak wilt remediation starts with digging a trench around the perimeter of the infected trees.
The Michigan Department of Natural Resources custom-designed a five-foot-long trenching blade to address the fast-spreading fungus. There are only three such blades in the state.
"It goes five foot deep to make sure we sever all the roots that come from the red oak trees – they grow as deep as five feet," said arborist Josh Gleason.
Phase two of the process will take place at the start of the new year when the trees will be felled or cut down.
City officials said they plan to partner with a reclamation company to see if any salvageable timber can be repurposed.
Gleason said there has to be a wound on the tree's exterior for the disease to be deposited by the beetles. Wounds are typically caused during the pruning process.
"It's highly recommended to only prune oak trees during the wintertime," he said.
At the end of November, the city will hold an informational webinar for residents on how to identify the invasive fungus.