WORTHINGTON — Plant health specialists with the Minnesota Department of Agriculture hosted a public meeting in Worthington Wednesday to present information and options regarding Emerald Ash Borer.
The invasive pest, which attacks all species of North American ash, was discovered at Worthington’s Pioneer Village in late July.
In response to the discovery, the city has already marked 150 trees on public property that it intends to remove starting this fall. That’s a mere 10 percent of the estimated 1,500 ash trees growing on city-owned property in the community. Varieties of ash trees make up about one-fourth of trees on the city’s public green spaces.
“We chose 150 ash trees that looked the poorest,” said city forester Scott Rosenberg. “Just because there is an ‘x’ on the tree doesn’t mean there’s Emerald Ash Borer in the tree. We marked the trees that didn’t look as good as other trees in town.”
Thus far, there have been no other reported findings of Emerald Ash Borer (EAB) in ash trees in Nobles County.
Minnesota is home to approximately one billion ash trees — the most of any state in the nation. EAB has been confirmed in 19 Minnesota counties to date, with the latest announced earlier this week in the Steele County community of Medford.
In southwest Minnesota, EAB has been confirmed in both Nobles and Martin counties. Both are under quarantine, meaning that no form of ash or hardwood firewood may be transported outside the county.
“You never know what’s in a piece of firewood,” said Jennifer Burington, MDA plant health specialist. “Do not transport firewood.”
She also asked residents to refrain from doing any work with their ash trees unless absolutely necessary until after Oct. 1 and continuing through April 30. Adult beetles are most active from May 1 to Sept. 30.
There are several options for handling ash trees that are taken down. They can be milled for lumber, grinded into wood chips or burned.
“Try to use as much as you can,” encouraged MDA Nursery and Export Inspector Danielle DeVito. “There’s going to be a lot of ash material in the system. It’s still good to use … as lumber.”
One meeting attendee asked if the city would pick up ash trees if homeowners cut them down on private property and put them on the boulevard.
“With the amount of trees we have and the limited staff, I would say ‘no’,” said Worthington Public Works Director Todd Wietzema. “We don’t have the resources to take care of what’s on our public property. If the resources would be available, we would take a look at that.”
Wietzema said property owners wanting to dispose of the trees should transport them to Schaap Sanitation, which is where the city will be disposing of the ash trees it cuts down. Wietzema said the city won’t be doing any tree removals until after Oct. 1, as the MDA advises.
Wietzema said if people need help in getting their ash trees cut down, there are a number of tree removal businesses in the area. The trees should be cut even with the ground so that there is no bark available for EAB larvae to invade.
Cutting down the ash trees isn’t the only option. There are treatments available that can be applied to the trees to protect them from EAB. These treatments should be applied before the tree is impacted, or while it still has at least 70% of its canopy remaining.
Treatment can be costly, however, noted Burington, quoting prices of $6 to $10 per diameter inch on each tree. That can add up to $80 to $150 per tree, and the treatment is effective for only two or perhaps three years.
Most chemical applications require applicator certification, so Burington encouraged people to hire a professional if they choose to treat their ash trees — especially the larger ash trees.
Wietzema cautioned the public to be careful when hiring chemical applicators.
“Ask for information and references,” he said. “Make sure you’re working with somebody that you trust.”
Burington said people should decide sooner rather than later if they want to use the treatment. Most have a late spring-early summer application window.
“Treatment goes on for however long you want the tree to live,” Burington said. “It is a lot of property value if you have a large tree on your lot.”
She said homeowners wouldn’t need to treat all of their ash trees at the same time, but could perhaps stagger treatment and treat some each year to get into a rotation.
If a property owner has an ash tree on the boulevard that they would like to save, Wietzema said they would be allowed to treat the tree.
“We’ll have to know who’s treating it, what trees and when they are treating it,” he said. “We would love nothing more than to have these boulevard trees. It’s just not financially feasible to spend $200 per tree for 1,500 trees.”
It is possible the Emerald Ash Borer could be killed during the coldest of winter days (it has to reach minus-29 under the bark of an ash tree for at least a couple of hours), but the surest way to kill the pest is through treatment.
Signs of EAB
Emerald Ash Borers are green metallic colored beetles. The females lay eggs on the outside of ash tree bark, and their larvae develop under the bark. It takes a year in most cases, sometimes two years, for the borer to complete its life cycle. Adults emerge as beetles that feed on ash tree leaves from about May 1 through the end of September.
The population grows at a steady pace, and Burington said an ash-lined street can look just fine one summer and three years later will have trees that are completely dead. The smaller the ash tree, the quicker the death.
To search for EAB, first identify the ash trees on your property. In general, they have opposite branching, compound leaves and diamond-shaped bark at the base of the tree. There are numerous cultivars of black, green and white ash growing in Worthington, and all can expect to be impacted by EAB. Burington said mountain ash is not impacted by EAB, and blue and Manchurian ash typically aren’t attacked by the beetle unless the trees are already stressed.
People can look for the presence of green metallic EAB beetles on the tree’s exterior, or remove some of the bark from an ash tree to look for an S-shaped gallery. There is also a D-shaped exit hole in the bark that is an indicator of the presence of EAB.
“If you see a D-shaped exit hole at eye level, likely the tree has had EAB for five years,” Burington said.
Perhaps the easiest and cheapest way to search for EAB is to look for woodpecker damage — holes that are dime-sized, light colored and oval shaped, she added. Also noticeable is the loss of canopy and a general thinning of the leaves, as well as a blonding (whitening) of the bark.
Individuals who suspect they have a tree affected by EAB are asked to report the discovery as soon as possible. In Worthington, people may contact the city forester. Other options include emailing firstname.lastname@example.org, calling 1-888-545-6684, using the Great Lakes Early Detection Network downloadable app or visiting the website mda.state.mn.us/arrestthepest.