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City takes proactive approach on EAB

Emerald ash borer.

An invasive, wood boring green beetle may be tunneling under ash tree bark now in Farmington that could lead to Emerald Ash Borer tree disease.

"EAB has not been found in Farmington yet it does not mean that it is not here," said Katy Gehler, public works director and city engineer with the City of Farmington.

EAB has infested ash trees in Eagan, Apple Valley and the Lebanon Hills and Burnsville areas.

Katy Gehler

"It is not far away and what we have heard, as it relates to EAB, is that it can be a community for a few years before it actually becomes visible," Gehler said.

EAB disease

The beetles' larva tunnels under tree bark and cuts off a tree's nutrients and water supply. The disease causes tree canopy dieback and eventually trees die.

"The beetles lay in the ash trees and the eggs turn into larva and as they are eating and growing, they tunnel their way under the bark," Gehler said. "The problem is as they do that, they enter the vascular system of the tree that is like our system that carries blood and oxygen, and it carries the water and nutrients and that is how the tree lives, so when they tunnel through that system, it ultimately kills the tree."

An estimated 44 percent of Farmington city boulevard trees are ash trees. The city has been working for years to develop a tree inventory of trees growing on public property.

After studying the tree disease from Michigan and Ohio, cities have learned the best ways to respond proactively and be prepared for a potential EAB infestation.

Showing photographs of how harmful EAB disease destroys trees, Gehler said "This illustrates how quickly it can impact the urban forests, and that is what we are learning from the cities where it hit, so we try to plan for a way to mitigate for EAB."

When EAB strikes cities and neighborhoods, trees' vascular system is compromised and branches become dry and brittle and can become a public safety hazard if they fall down.

City treatment

Cities plan for treatments and injection programs. Arborists come in like tree doctors and tap into trees to give injection treatments every year.

Many trees across the country were lost during the 1970s Dutch elm disease.

"What was known at the time was that ash trees were known to be a very urban tree that were grown in an urban environment because they grow relatively quickly," Gehler said.

Because ash trees grow quickly, they became popular replacement tree species for Dutch elm trees.

Since about 3,300 ash trees grow in Farmington, the city has developed an action plan and treatment strategy.

"If we going to treat them all, it would get very expensive, historically with the pricing," Gehler said. "One thing we have learned that helps with the spread of it was to relieve the pest pressure and keep the population of the beetles down."

Some cities have decided to remove 20 percent of the ash tree canopy and replace it preemptively because at the time, it was cheaper to remove and replace than it was to treat, Gehler explained.

"We are fairly certain that ash trees are going to succumb to the EAB at some point, and these trees have a lifespan so they are most likely going to have to be removed," Gehler said.

Disease projection

The city projects EAB disease will hit Farmington within a relatively short period of time or about 10 to 11 years, Gehler said.

"I think some cities were trying to spread out the removal and replacement and get new trees in the ground so they would start to grow," she said.

But today tree treatments have become more prevalent after more information is known about the tree disease and how to combat EAB. The general guidelines are to treat trees every two to three years to protect the trees, Gehler said.

The cost for treatment has come down in the past few years. The city will review and assess the ash trees health and quality and rate the tree with a good, fair or poor rating, depending on the trees' condition and size.

"Trees that have declined to a certain point may not be treatable and may not be needed in the treatment program," Gehler said.

The city decided if ash trees are 15 inches or greater in diameter, these trees can be placed on a treatment schedule. Those ash trees include boulevard and city park trees, but not ash trees growing in natural, undeveloped areas of Farmington.

Homeowner program

The city has a homeowner ash tree program where homeowners can work directly with a company and a certified arborist who can visit and provide a tree review. Then a cost proposal will be available for homeowners to pay.

"The treatment does come with a warranty from the company so if the tree were to die from EAB, the homeowner would be refunded the cost of the tree," she said.

Gehler said "Some residents called up and said 'I have an ash tree in my front yard and it looks really bad and can the city come and remove it because it looks really bad?' "

When homeowners receive a consultation, there is an incentive to treat the tree that falls under the right condition.

"If a tree has declined, they are not going to recommend this treatment," Gehler said.

The city has identified at least 318 trees in Farmington that fall under the poor quality condition. Later this year and throughout the winter, the city plans to remove the poor quality ash trees in decline.

"Ultimately, 940 ash trees have been identified for treatment and we are putting them on a three-year rotation treatment schedule."

Emerald Ash Borer tree disease

What: Emerald Ash Borer tree disease is present in Dakota County. Farmington has developed an inventory of trees growing on public property and 44 percent of city boulevard trees are ash trees.

Why: Farmington property owners can identify ash trees on residential property, look for signs of EAB, and contact a certified arborist to evaluate treatment options.

How: Farmington City Council adopted an EAB Management Plan this spring. The plan calls for the removal of boulevard ash trees rated in poor condition. The plans calls for an injection of insecticide targeted at the beetle larva on public trees in good to fair condition and growing 15 inches or more in diameter. The plan calls for treatment of trees on private property.

The City of Farmington contracted with YTS Companies, a professional tree care service to provide EAB an injection treatment for ash trees on public property. Reduced pricing is also available to Farmington residents to treat ash trees on private property. Residents will be responsible for the full cost of treatment.

Deadline: Farmington residents who want to schedule treatment for ash trees may contact YTS Companies at(612) 331-1133. Contracted prices are valid through the end of the 2017 season. Ash tree injection treatments are recommended from June 1 and Sept. 30 when EAB larvae are most active.

More information: To learn more on the city's Emerald Ash Borer plan, visit the city website at bit.ly/2rD39bS.

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