Emerald Ash Borer discovered in Fond du Lac
The city of Fond du Lac has discovered an ash tree infested by emerald ash borers in the southwest part of the city, the first time the pest's presence has been confirmed within the city limits.
Wisconsin Department of Natural Resources ash borer expert Bill McNee helped confirmed the find and said the find means the insect has had years to make itself at home here.
"It is virtually impossible (to eradicate emerald ash borers)," McNee said. "By the time you find it in an area it has had four or five years to fly all over town. ... You just can't find the true edge of the population."
Approximately 5,000 publicly owned trees are expected to be destroyed by the ash borer over the next decade, the city said in a press release. Thousands more privatley owned trees in the area are expected to perish.
"In the next three to five years we'll see an explosion of ash (tree) mortality," Fond du Lac Director Of Public Works Jordan Skiff said.
The ash borer could kill more than 99 percent of the ash trees in the state, experts say, which would account for more than 725 million trees and more than 20 percent of the state's urban forests, according to the DNR.
Skiff said the insects' presence was discovered by the city arborist, who has been checking dying and dead trees for ash borers since it was discovered in the area.
McNee said although the ash borers were just discovered, they've likely been within the city limits for several years.
Trees victimized by the insect usually don't show signs of infestation until two or three years after the insects arrive, he said. The ash borers spend 10 to 11 months inside the bark of the tree, he said, which also makes it difficult to find.
"The discovery represents a significant concern to the city, as a large number of public and private trees within the Fond du Lac community are ash trees," said Skiff in a written statement.
Skiff said the city will take several steps to curb the ash borer's spread. The city will selectively remove as many ash trees as its budget will allow. He said the city will space out ash tree removals and sometimes plant new trees to mitigate the impact on any one neighborhood.
The city also plans to chemically treat as many trees as possible under budgetary constraints. Skiff said trunk injection treatments are almost 100 percent effective in protecting trees.
The earlier a tree is treated the greater its chance of survival, he said.
"Despite our desire to see many ash trees saved, the reality is that we don't have the budget to treat 5,000 ash trees," Skiff said.
Skiff said the treatment cost is about $120 for an average 15-inch diameter tree, which needs to be reapplied every two to three years. Other less expensive treatments exist but are less effective, he said.
Skiff said he anticipates a point in the future when the city may require residents to remove dead ash trees through the public nuisance ordinance. He said he expects a sharp increase in the number of downed ash trees in coming years and the city may need to designate an area to store the wood.
Fond du Lac County was placed under quarantine when Wisconsin's first infestation was found in neighboring Washington County in 2008.
McNee said the ash borer was most likely introduced to the area through infested firewood from another area.
"Which is why we have these quarantine laws and educational campaigns," McNee said.
He said the ash borer could have also been introduced through infested wooden pallets or crates.
The ash borer kills almost every untreated infested tree. The city has been preemptively removing ash trees for several years to prepare for an infestation, according to the press release. Several dozen residents have treated trees at their homes and businesses with chemicals to protect against the insects.
The ash borers only infest trees that are true ash species. They are not poisonous and do not bite, McNee said.