Up to 4800 city ash trees expected to die

by Luke Ulatowski
For The Beacon







ASH TREES near the La Ferme Road subdivision in the Town of Plymouth illustrate before and after a borer infestation. – Beacon Photos by Kay Preissner

SHEBOYGAN – A tree-killing insect infestation that was officially confirmed in Sheboygan three years ago has grown to extreme proportions.

“At this point, I would assume that every ash tree in the county has emerald ash borer in it,” City Forester Tim Bull said.

As part of their Restoration of Our Trees Sheboygan (ROOTS) campaign, Lakeshore Natural Resources Partnership and Sheboygan Rotary Club held a two-hour presentation all about the threat of the emerald ash borer at Maywood Environmental Center on June 13. Speakers included Bull, ROOTS Coordinator Tony Fessler and arborist Bob Gluck of Hoppe Tree Service.

The emerald ash borer is native to East Asia. It migrated to the United States through wood pallets that were delivered to the Detroit area in the late 1990s.

“Of course, the bug didn’t remain in the pallets and found its way into the ash tree population,” Fessler said. “Unfortunately, what the environmental authorities over there found was that there wasn’t an easy way to combat it. Maybe if they had gotten to it right away, burned the pallets, understood what they were dealing with, maybe there would’ve been a chance of stopping it, but at this point, we’re well beyond that.”

Over time, the infestation spread through lower Michigan, then into Indiana and Ohio and later Illinois. Now, it is working its way north through Wisconsin, which Fessler believes is an ideal home for the ash borer.

An adult emerald ash borer–smaller than a penny–lays its eggs on ash trees. As the larvae grows, it tunnels beneath the bark and develops for one to two years. In adulthood, the ash borer lives up to its name and eats away at the inside of the tree, creating what Fessler called “S-shaped” tunnels. The damage is irreversible.

Depending on its size, an infested ash tree will die completely between one and four years. Upon exit, the ash borer leaves a tiny D-shaped hole in the tree that serves as a clear indicator of infestation.

In March 2016, the Department of Natural Resources confirmed that the emerald ash borer was found in a Sheboygan tree on Ontario Avenue. At that point, a city-wide infestation was unstoppable, and according to Fessler, things are looking especially grim now. Due to the time it takes for an ash borer infestation to kill a tree, mortality rates are just now rapidly rising. ROOTS estimates that 30%-70% of Sheboygan County ash trees will die in the coming years.

“I’m not even sure we can stop it,” Fessler said.

The emerald ash borer only affects true ash trees. Unfortunately, those make up a huge chunk of Sheboygan’s tree population. Fessler presented tree population estimates recorded 10 years ago. In urban Sheboygan, there were 30,720 trees, 6,921 (23%) of which were ash. Rural estimates were higher, with ash trees taking up one-third of the tree population. These numbers do not include trees on private property.

Action against the emerald ash borer is coming from several institutions. ROOTS is working to establish an investment fund for reforestation. It is also hiring volunteers to take part in reforestation while conducting and maintaining up-to-date tree inventories. The June presentation was part of ROOTS’ “Community Engagement” initiative.

Bull highlighted the city’s emerald ash borer management plan. All ash trees with less than a 12-inch diameter and less than 4.5 feet above ground DBH are marked for removal. Meanwhile, the “most desirable” 2,400 ash trees have been treated with insecticide. The rest of the untreated ash trees are to be removed.

The treatment entails a trunk injection of emamectin benzoate–5 millilitres per inch DPH. The treatment must take place early on in an ash tree’s infestation and, after that, take place regularly every two years. 1,200 ash trees were treated in 2017, and another 1,200 were treated in 2018. According to Bull, that means 800 trees must be treated every year from here on out.

Bull looks to remove another 2,037 identified ash trees. The management plan only accounts for ash trees deemed particularly important such as those on city streets and near playgrounds. Most ash trees in parks and woods are not counted.

This year, the city has planted 540 replacement trees. Bull’s goal is to have 100-200 more planted each year. The city is taking care not to plant too many trees of the same type in order to avoid catastrophes similar to the emerald ash borer infestation and the Dutch elm disease epidemic that mitigated Sheboygan’s once-massive elm tree population in the mid 80s.

Gluck and his company Hoppe Tree Service provide treatment for infested ash trees on private property. Gluck employs the same emamectin benzoate treatment as the city, calling it the only effective method. However, according to Gluck, even an ash tree treated early on in its infestation has only a 70% chance of surviving.

Questioned about the price, Gluck stated that on average, treatment covers 15 inches for $10 per inch, adding up to $150 every two years.

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