OWATONNA –The boardroom at the Steele County Administration building was filled to the brim as people desperate to save their ash trees learned more about the most recent threat to the county.
Emerald ash borer – an invasive insect whose larvae kill 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 – was first discovered in Steele County in the beginning of September. The Minnesota Department of Agriculture confirmed at least four trees in Medford that have an emerald ash borer – or EAB – infestation.
Though that is the only infestation confirmation within Steele County thus far, the entire county was placed under a quarantine that limits the movement of hardwood firewood. To help the residents better understand what they are up against, the MDA hosted an open house forum on Tuesday night at the Steele County Administration building. During the meeting, staff from the MDA and the University of Minnesota Extension Office discussed all things EAB, ash trees, and the quarantine.
Jennifer Burington, a plant health specialist who works exclusively with EAB infestations for the MDA, gave a presentation to the group of more than 50 locals regarding the life cycle of EAB, how to identify and infestation, and treatment options.
“During the summer, you’re only going to find adult beetles up in the canopy of ash trees,” Burington stated. “They aren’t going to be buzzing around your head or hanging out on the ground, so chances are you’re not going to catch infestation that way.”
The canopy of ash trees , which is the most upper layer of a matured tree, is where Burington stated most everything can be spotted in terms of EAB damage and infestation. Most notably, about two years into the infestation is when Burington said one can see the signs of woodpecker damage in the top third of an ash tree. Because the larvae are directly under the bark and then make pupa chambers about a quarter of an inch into the wood, woodpecker holes that are about a dime-sized and oval-shaped will be found near the top of infested trees.
“You will also see blonding area in the bark where the bark is sloughing off,” Burington added about the woodpecker damage. “We like the woodpecker because the woodpeckers go after the EAB.”
While the EAB larvae are tunneling beneath the bark, creating s-shaped galleries, Burington said that the bark may split open – another visible sign of infestation. This stage can be seen around the third year of an EAB infestation as more and more eggs are being planted on the outside of the tree, leading to a larger population of larvae tunneling under the bark. Other damage includes a D-shaped emergence holes once the pupa becomes an adult beetle.
By the fourth year of an infestation, Burington said that the impact on a trees canopy will be visible as it starts to thin out and branches begin to die. By about the sixth year of the infestation is when Burington said a homeowner or city will simply have a dead ash tree.
“It is very important to know that when an ash tree is dead it becomes very brittle and very hazardous,” she explained. “This can make it more expensive for a tree service to remove and can also cause issues when storms come through and can easily take them down.”
To help manage the infestation and slow the growth of EAB, Burington encourages those living within the quarantine to do all of their trimming and tree removal during the insects “off season.” Between Oct. 1 and April 30, Burington said that EAB is essentially hibernating under the bark and therefore unable to easily transfer to a new tree when being removed. Burington added that EAB infestations typically migrate from one to two miles a year, though an adult EAB can fly up to five miles.
“They mostly travel through firewood,” Burington asserted.
The quarantine specially prohibits the transportation of ash and EAB outside of the quarantine area, as well as all hardwood firewood less than four feet in length. All ash, however, cannot leave a quarantined area without a compliance agreement from the MDA.
“Transporting firewood out of a quarantine comes with a $7,500 fine a day per occurrence,” Burington said. “Do. Not. Transport. Firewood.”
While firewood within a quarantined area cannot travel to an area that isn’t quarantined, Burington said that firewood can be moved from one quarantine to another. For example, a resident of Steele County cannot bring firewood into Waseca County – which is not under a quarantine – but can bring firewood into Dodge County, Olmsted County, Wisconsin, or Iowa – all quarantined areas. Firewood from areas not in quarantine may also be brought into quarantined areas. A map of all the quarantined areas in Minnesota can be located on the MDA website at mda.state.mn.us/eab.
Burington also encouraged all Steele County residents to start making a plan for their ash trees, even though Medford is the only known location within the county to have a confirmed infestation at this time. She suggested that property owners start evaluating which trees that would like to try to save through treatment and which trees could possibly be removed.
“You can also do nothing and wait and decide what you will do late, but I will warn you that it will still come back to either treating or removing the tree,” Burington said. “And if you wait too long, removal may be the only option.”
Ash trees that have at minimum of 50% of a healthy canopy are viable candidates for treatments, according to Burington, because they are only about two to four years into the infestation. She explained how treatments are not a “one time” ordeal, however, and that trees will likely have to be treated every other year until an infestation is controlled.
There are four types of EAB treatment options: soil injection, trunk injection, bark spray, and canopy spray – all types of insecticides. According to Jeffrey Hahn, an entomologist with the University of Minnesota Extension, 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. Burington added that large trees are best treated by a professional.
Some people brought bark samples with them to the meeting to ask the professionals if they had an EAB infestation, though none were discovered at the meeting. Others also asked a variety of questions regarding their specific property, including a representative from the Owatonna Country Club that stated there are about 500 ash trees on the club’s land and that they are worried about the 200-some that are located along the river. The MDA staff directed the representative to contact the local Soil and Water Conservation District and hydrologist. The club has removed about 100 ash trees in the last handful of years and has already identified 75 that they would like to treat.
Others at the meeting wanted to know how long they can expect their neighboring counties of Rice and Waseca to also be quarantined, which Burington said there is no definite timeline.
“I can’t answer when they will be quarantined because it all depends on the people and if they are protecting their trees,” Burington said. “I can say that I stopped many times on my way to Nobles County recently, especially in Rice County, to look at ash trees off the freeway and I didn’t see anything extremely obvious at this time.”
“I wish I could say where it’s going to spread, but I can’t,” she continued. “EAB attacks any ash tree, health, sick, small, large. All the ash trees are at risk.”
It will be up to local municipalities to decide how they want infested ash trees to be discarded if they are to be removed. Burington said that chipping the material is a good option or burning all of the tree so that nothing can survive, but it will be up to each city or county within a quarantine.
Medford City Council discussed during their September meeting the need to identify a compost area within city limits to try to prevent the infestation from spreading beyond the town. Owatonna city staff have also been working on developing a plan to best prevent the EAB from taking over the many trees in their parks and along their boulevards, but first need to do a total tree inventory in order to move forward.
The public has 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 proposed to adopt the quarantine on Nov. 1. The quarantine limits the movement of ash trees and limbs, and all hardwood firewood out of the county. The proposed quarantine language can be found at mda.state.mn.us/eab.
The MDA encourages anyone from the public to report any potential infestation or send in pictures of their own ash trees if they believe they may be damaged to firstname.lastname@example.org.