MEDFORD — Beautiful, but deadly.

The lives of Steele County’s ash trees are in serious threat as the first detection of an invasive beetle in the area has been confirmed by the Minnesota Department of Agriculture.

A tree care professional contacted the MDA last week after they noticed several dying ash trees at a site in the city of Medford. MDA staff were able to find live emerald ash borer — or EAB — and collect a sample for federal identification. That confirmation came Wednesday morning from the U.S. Department of Agriculture.

The adult emerald ash borers are flying, metallic emerald green beetles which feed on the leaves of ash trees. Their life cycle is short and precise as they lay eggs in bark crevices. It is the larvae that are the true killers, murdering the ash trees from the inside out by tunneling under the bark and feeding on the part of the tree that moves nutrients up and down the trunk.

The invasive insect was first discovered in Minnesota in 2009 and is now found in 35 states. Minnesota is highly susceptible to the destruction caused by EAB. The state has approximately 1 billion ash trees, the most of any state in the nation.

“It is very common for infestations to be found along major highways like Interstate 35,” said Jeffrey Hahn, an entomologist with the University of Minnesota Extension. “The emerald ash borer in Medford probably came from people carrying firewood or ash wood.”

Hahn explained that a number of trees in the Medford site had already died or were dying when the MDA was alerted, meaning that the infestation was by no means new. Taking a “wild guess,” Hahn said the infestation could have happened three to five years ago, but that it has definitely been around for more than a year.

“It is very possible that it is already in other areas of Steele County,” Hahn added, pointing out that the insects have been confirmed in both Goodhue and Dodge counties as well. “Considering it’s in neighboring counties, it’s not really surprising that it’s found their way to Steele County.”

Because this is the first time EAB has been identified in Steele County, the Minnesota Department of Agriculture will be enacting an emergency quarantine to limit the movement of firewood and ash material out of the county. This will reduce the risk of further spreading the tree-killing insect. A total of 20 Minnesota counties, including Steele, are now under a full or partial quarantine to prevent the spread of this highly destructive tree pest.

“We rely on partners in our tree care, logging, and landscaping industries to help us monitor for emerald ash borer and other invasive pest,” said Mark Abrahamson, director of MDA’s Plant Protection Division. “However, we also need every Minnesotan to be vigilant.”

“Know and look for signs of invasive pests; don’t move firewood and other materials around that may transport these insects,” Abrahamson instructed. “And report anything unusual to us at the MDA.”

Hahn suggested the first step residents in Steele County take is to identify the trees on their property. If they do have ash trees, it is important to check the condition of the trees, according to Hahn.

“It your tree looks big and healthy then our guidelines is if it is within 15 to 20 miles of an infestation that you should considering trying to treat it,” Hahn said. “Some people like to wait until an infestation is closer, but that is always kind of a gamble.”

There are four types of EAB treatment options: soil injection, trunk injection, bark spray, and canopy spray – all types of insecticides. According to Hahn, the most common treatment is the trunk injection, which targets the larvae tunneling in the tree and stops the most destructive phase of the insect. Hahn added that this treatment makes any potential exposure of the insecticide extremely minimal if any at all.

“I don’t want everyone in Steele County thinking that they need to go out and spray,” Hahn added. “Not knowing exactly where the infestation is, a person could reasonably wait until there is more evidence of it being closer.”

“There’s not really a right answer,” Hahn continued in regard to who should be proactively treating their ash trees. “If someone decided that want to wait they can, but if someone had a prized ash tree in their yard they would be justified to treat and protect it.”

Jennifer Burington, a plant health specialist with the MDA’s Plant Protections Division, said that come this fall the MDA will be further investigation the Steele County infestation so that they can gain more knowledge on how far the infestation has spread.

“We wait for all the leaves to come off the trees so that we can look for woodpecker damage,” Burington said, stating that they always start where the infestation was found and start to move down the road from there. “We will be reaching out to the city of Owatonna and the city of Medford to look at doing further surveys. If we continue to find it further out than we will keep going until we don’t find it anymore.”

Residents of Steele County are also invited to an open house on Tuesday, Oct. 1, regarding the discovery of emerald ash borer in the county. The open house will be held in the board room at the Steele County Administration Building from 6 p.m. to 8 p.m. Those attending the open house will have an opportunity to learn more about EAB and local options to deal with the insect and hear how residents can limit the spread of the bug. Experts will be available to answer questions.

Comments can be made at the open house or by contacting Kimberly Thielen Cremers with the Minnesota Department of Agriculture via email at

The public will also have an opportunity to provide input on the proposal to add Steele County to the state formal quarantine. The MDA will take comments on the proposed formal quarantine through Oct. 25 and proposes to adopt the quarantine on Nov. 1. The quarantine limits the movement of ash trees and limbs, and hard hardwood firewood out of the country. The proposed quarantine language can be found at

People are always welcome to report any potential infestation or send in pictures of their own ash trees if they believe they may be damaged to

Reach Reporter Annie Granlund at 444-2378 or follow her on Twitter @OPPAnnie.

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