Local officials react to emerald ash borer confirmation

Emerald ash borer was confirmed in Worthington on Monday. What does this mean for Nobles County, Worthington and homeowners?

Emerald ash borer pioneer village
Ash trees die on the northern tree line between Pioneer Village and Interstate 90 as the emerald ash borer larvae feed under the bark. (Tim Middagh/The Globe)

WORTHINGTON — Although this week’s announcement that the invasive emerald ash borer has been confirmed in Worthington wasn’t welcome news, to some it wasn’t surprising, either.

It was only a matter of time, said Worthington Public Works Director Todd Wietzema, that the invasive and destructive beetle would be discovered in Worthington, especially considering it had previously been reported in Martin County and South Dakota’s Minnehaha County.

Interstates are hot spots for spreading the disease, which is shown on MDA’s online emerald ash borer status map .

“I was just waiting for the day,” Wietzema said about what he expected was inevitable. “I was hoping the day was a lot further off.”

The first EAB case in Nobles County was confirmed Monday by the Minnesota Department of Agriculture. The sample that tested positive was taken from an ash tree between just beyond the Pioneer Village fence and Interstate 90.


Emerald ash Bore larva lines
An ash tree's bark is cut back to confirm the presence of the emerald ash borer in the northern tree line between Pioneer Village and Interstate 90. The pattern is caused by the bettle's larva. (Tim Middagh/The Globe)

The MDA made its official announcement Wednesday, placing Nobles County under an emergency quarantine. The quarantine prohibits people from transporting any tree-type hardwood out of the county.

To read the official emergency quarantine declaration, click here .

Locals react

Nobles County Historical Society board member Ron Wood said the line of trees in question have looked like they do now for at least the past year — since he's been maintaining the Pioneer Village grounds.

What's even more concerning than the trees discovered just beyond the fence is what it could mean for the rest of the village's trees, which Wood said are mostly ash. He said the board will have to discuss its course of action.

The city of Worthington and Nobles County are also considering how to respond to the new discovery.

Wietzema said city personnel are in their information-gathering phase. Nobles County Public Works Director Stephen Schnieder said county commissioners had been made aware of the find, but are awaiting further guidance from MDA’s Sept. 4 public meeting to determine its course of action as it relates to county’s ash trees.


The focus, Wietzema said, is taking action to minimize the spread.

According to Wietzema, the city has recently undergone a routine inspection of its boulevard trees. The crew has marked some storm-damaged and other problematic boulevard trees around town for its first round of removals, but Wietzema said that isn’t related to the EAB confirmation.

“We did an initial markup of ash trees, too, since we knew this was coming,” Wietzema said. “The (ash trees) marked at this time have other issues — structural, deadwood. We did not mark any healthy-looking ash trees at this time.”

Having previously discussed potential action should EAB be discovered, Wietzema said the city then decided it would opt to remove rather than treat its ash trees. There are approximately 1,500 ash trees on public property in Worthington, which includes boulevards and manicured parks and properties, he said.

“I can’t even tell you how many ash trees there are on private property in town,” Wietzema said. “And I don’t know exactly how we’re going to deal with those yet.”

Wietzema said he will propose a 10-year removal plan of the city’s ash trees, which would eliminate approximately 150 ash trees annually. Costs will be dependent if the city can remove the trees in-house, or if it will need to contract the work — hiring could cost $100,000 a year. The city council has not taken official action, and Wietzema expects an upcoming work session.

Regardless of what the city council decides, Wietzema said city ash trees won’t be removed until after Sept. 30, which is the best management practices from MDA based on the bug’s active time frame and likelihood of spreading the disease. Wietzema asks that homeowners follow MDA’s recommendation and not trim or cut ash trees between May 1 and Sept. 30. According to the MDA, the beetle actively searches for new hosts within that time frame.


Emerald ash Bore hole
D-shaped exit hole left by an adult emerald ash borer in the bark of an ash tree between Pioneer Village and Interstate 90. (Tim Middagh/The Globe)

The EAB disease isn’t the first major threat to an entire population of city trees. In its July 10 edition, The Globe published a Looking Back column about the discovery of Dutch elm disease 50 years ago.

“After many months of apprehensively waiting for the bad news to arrive, the city of Worthington had two confirmed cases of Dutch elm disease," the article published 50 years ago states. According to the article, Dutch elm disease was first discovered at two residences on South Shore Drive.

Many ash and maple trees were planted to replace the diseased elm trees, said Wietzema and city forester Scott Rosenberg.

“Part of that (reasoning) was that they were fast growing and could repopulate the town,” said Rosenberg, who also owns a private tree business, Rosenberg TreeScapes.

Wietzema said that practice has since changed. Now when trees within the city are removed, they’re replaced with a number of tree varieties.

Rosenberg said the city hasn’t planted ash trees for the last eight to 10 years, anticipating the disease.

“If you’re going to try to find a silver lining, it’s a good thing this bug doesn’t attack maple trees, because the city has an even higher population of maple trees than ash (trees),” Rosenberg said.

The recent EAB news didn’t surprise Rosenberg, either.

“I’ve been saying for years that I wouldn’t be surprised if it was here for years, but we just haven’t found it yet,” he said. Multiple online resources indicate that the damaging insects may be present in a tree between three and five years before the symptoms are identified.

Rosenberg expects that Worthington will lose “most, if not all” ash trees, depending on how private homeowners choose to respond to the disease.

Homeowner outlook

Rosenberg said homeowners with ash trees have three options to consider now that EAB has been confirmed in the area. One is do nothing and wait until their tree becomes infested to remove the tree.

“And just buy time so to speak and cross their fingers that it takes longer than showing up there sooner,” Rosenberg said.

The potential risk with that option, Rosenberg said, is that once a tree becomes infested, it becomes much more brittle and a threat to personal safety and property than an ash tree that would die naturally.

“They become a hazard tree in a much shorter time than any other diseased tree,” Wietzema said.

There are also two chemical treatment options: soil-drench and injections.

With the first option, a homeowner may apply the chemical around the base of the tree near the root system. The tree then pulls that chemical up through its root system as it moves water up.

The second method requires drilling holes into the trees and injecting it with a chemical treatment. Rosenberg, a licensed treatment provider, said this option requires a pesticide applicator’s license. This method, unfortunately, isn’t cheap, he added.

“The bad thing is that regardless of what method you use to chemically treat, it’s not a do it once and you’re done,” Rosenberg said. “You’re going to continue to do this over time.”

Ash tree leaves
Leaves of an ash tree. (Tim Middagh/The Globe)

Rosenberg — who has treated ash trees in Worthington belonging to homeowners anticipating the disease — said there are a number of reasons people may decide to treat their ash trees, including sentimental value and the shade they provide their home.

Rosenberg highly recommends that homeowners wanting to save their ash trees consider chemical treatment sooner rather than when their tree starts showing symptoms, as it will likely be too late.

Wietzema said if homeowners would like to save ash trees on their boulevard, treatment would be at their expense and they would need to make arrangements to hire a city-approved treatment applicator.


A Sept. 4 EAB open house has been scheduled for Nobles County residents. Residents may attend between 6 and 8 p.m. in the Farmers Room of the Nobles County Government Center, 315 10th St., Worthington.

Attendees will have the opportunity to learn more about EAB, local options to deal with the bug and ask questions to experts. The public will also have an opportunity to provide input to the county's formal quarantine.

MDA will accept comments on the proposed formal quarantine through Sept. 25, with plans to adopt the formal quarantine Oct. 1. Input may be directed to Kimberly Thielen Cremers at

According to the MDA, it isn’t uncommon that more infected trees are reported from an area once word of the first official confirmation spreads.

If area residents believe they have an EAB infested tree, they may report it to the state’s Arrest the Pest plant protection program: 1-888-545-6684;

Reports may also be made on the Great Lakes Early Detection Network app, which is available to download on smart phones. Further EAB information is available on the MDA’s website.

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