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Look out for ash borer, city pleads
Late winter a good time to stop the pests before they spread
With 12 ash trees found infected with emerald ash borer in the Dayton’s Bluff neighborhood of St. Paul, officials are encouraging residents in the area, and statewide, to look out for signs of the pests before spring gets underway.
Emerald ash borers are invasive Asian beetles whose larvae destroy ash trees by feeding on the layer of the tree that transmits nourishment. They have no native predators here and have killed tens of millions of ash trees in the Midwest after first being discovered in southeastern Michigan and Windsor, Canada in 2002.
Dave Frederickson, commissioner at the Minnesota Department of Agriculture, and other officials visited the infected Dayton’s Bluff trees Tuesday, March 11, to urge residents to keep an eye out for emerald ash borer. Frederickson admitted that with such small, mobile pests, the fight against them is a matter of defense.
Rather than trying to eradicate the beetle from the state, he explained, “our situation is more to control the spread.”
And even that effort will take state, county and local participation plus the sharp eyes of residents who value the huge, shady trees in their yards and boulevards.
“The City of St. Paul doesn’t have the staff to do it all themselves,” Frederickson said. “We love trees in Minnesota, that’s part of the reason we live here.”
So far, on private property
The Dayton’s Bluff infestation, near Metro State University’s campus, was initially found in January by a staffer with the City of St. Paul’s Forestry department. The city had received a call about ash trees with suspicious-looking damage, and the staffer who examined the trees confirmed the caller’s fears.
Rachel Coyle works for St. Paul’s Forestry department and is heading the city’s effort to get ahead of the pest.
After identifying the infected trees, city forestry workers surveyed a ten-square-block area surrounding the infected site, Coyle said.
They found a total of 12 infected trees, not to mention a number of other trees that may be infected.
All of the infected trees are located on land not owned by the city. Aside from three on Metro State University’s property, the others were found in peoples’ yards.
The trees have been tagged by the city, requiring property owners to either treat or remove them.
Coyle noted that homeowners are responsible for taking care of trees on their property infected with EAB. This can mean cutting down trees or treating them, depending on the severity of the damage.
She said contractor bids for removing a tree range widely, since ash tree removal is a competitive market. She heard from one homeowner who had bids coming in as low as $900 and as high as $2,200 for the same tree.
Treating a tree generally costs about $10 per inch of the circumference of the tree, she said. With a tape measure, homeowners can measure the tree’s girth about four feet up from the ground to judge how much treatment may cost before calling for estimates.
If a homeowner doesn’t take care of an infected tree, the city will hire a contractor to remove it and charge the property owner for it, Coyle said.
Taking out public trees
Since EAB was first found in St. Paul in 2009, the city’s forestry department has been doing routine ash tree removal throughout the city, to try to prevent the spread of the pest. The city has cut down more than 5,000 public trees thus far, at a rate of 1,100 per year, to slow down the contamination of other public -- and privately owned -- trees.
However, Coyle said, a lot of the spread of the pest occurs in privately-owned trees that aren’t being so actively watched.
St. Paul doesn’t have a “go-to” replacement for ash trees it removes; instead it chooses from a variety. Many of the ashes in Midwestern cities were planted in the 1960s and ‘70s after Dutch elm disease denuded boulevards of their shade trees. With the newest scourge sweeping through the ash trees, cities have learned not to establish a tree monoculture.
Ways of tackling the problem
While there are no native predators for EAB in Minnesota, Abrahamson noted, the Minnesota Department of Agriculture holds out hope for tiny parasitic wasps that feed specifically on emerald ash borers and can help curb the population. The wasps are originally from China, where ash trees stands are able to survive the beetles; the wasps lay their eggs in beetle larvae, killing the larvae.
The Minnesota Department of Agriculture is working on bringing the wasps to the state.
The wasps have so far been brought to Winona County Great River Bluffs State Park, Abrahamson said.
Abrahamson noted that three counties in Minnesota were quarantined for EAB in 2009 -- Hennepin, Ramsey and Houston -- so that young trees and firewood can’t be moved in or out of them. Since then only Winona County has been added to the list, which he said looked good in comparison to other states who have seen fast growth of the pest.
Nonetheless, EAB poses a serious risk to Minnesota forests, as the state has the highest population of ash trees in the country.
Abrahamson said that while this year’s harsh winter could have curbed the population, it was hard to say how much of an impact the below-zero temperatures may have had.
People should still expect to see EAB in the Twin Cities, he said.
Once consulting a guide for EAB identification, residents can call the city’s Forestry department at 651-632-5129 to get help identifying an infested tree. For more information on EAB and a guide on how to identify a potentially infested ash tree, visit www.stpaul.gov/eab.
Contact Patrick Larkin at 651-748-7816 or at firstname.lastname@example.org. Follow him on Twitter at @ESRPatrickLark.
Tips for identifying EAB
• Be sure you’ve identified an ash tree. This is an important first step since EAB only feeds on ash trees. Ash have opposite branching -- meaning branches come off the trunk directly across from each other. On older trees, the bark is in a tight, diamond-shaped pattern. Younger trees have a relatively smooth bark.
• Look for woodpecker damage. Woodpeckers like EAB larvae and woodpecker holes may indicate the presence of EAB.
• Check for bark cracks. EAB larvae tunneling under the bark can cause the bark to split open, revealing the S-shaped tunnels the larvae make in the living wood layer.
• Contact a professional. If you think your ash tree may be infested with EAB, contact a tree care professional, your city forester, or the MDA at email@example.com or 888-545-6684 (voicemail).
For more identification help, go to https://www.mda.state.mn.us and search for EAB.