At the city border, ash borer threatens 20 percent of all of Minneapolis' trees
The Minnesota Department of Agriculutre has hung traps for the emerald ash borer — like this one at Brackett Park — in hopes of reducing the amount of damage to the city’s trees.
Minneapolis, a city known for its trees, has approximately 210,000 ash trees; that’s more than 20 percent of the total number of trees in the city. The emerald ash borer, recently detected in St. Paul near the Minneapolis border, threatens them all. Minneapolis has approximately 38,000 ash trees growing on boulevards, but most ash are on private property, according to the Minneapolis Park and Recreation Board (Park Board).
Park Board President Tom Nordyke says all the information the Park Board had received suggested the ash borer wouldn’t arrive for three years — optimistically five years. It has not crossed the Minneapolis border but it is clearly ahead of schedule. “We don’t’ have a plan,” Nordyke says. “We will have to figure it out. It will be in the context of a statewide solution.”
Park Board Commissioner Scott Vreeland refers to the emerald ash borer as “a hurricane or a flood that hasn’t happened yet” and “a ticking time bomb.” Vreeland, whose district includes Seward, the West Bank and Corcoran, says the city needs to clearly communicate a strategy to the public before the infestation hits.
The Park Board stopped planting ash in 2007. Options going forward include increased planting, slowing tree loss by using pesticides and removing trees — even healthy ones — to reduce the bugs’ food supply. “I want to connect the best science with the best politics,” said Vreeland, who also serves on the Minneapolis Tree Advisory Commission.
Volunteer efforts played a role in responding to Dutch Elm disease in the 1970s, identifying infected trees. That’s a tougher task for emerald ash borer, yet Minneapolis neighborhood groups now are beginning to look at what they can do. Carla Urban, co-chair of the Livability Committee for the Prospect Park East River Road Improvement Association, is developing an emerald ash borer task force. “My vision is we would serve as a source of information, see what is going on in other neighborhoods and learn from what they are doing.”
The Minnesota Department of Agriculture is the lead agency for statewide planning. It has emerald ash borer traps (large, purple contraptions) hanging in city trees, an early detection effort.
When the bugs hit, the response will be expensive. And the need comes at a time when money is especially tight.
The Park Board estimates the cost of removal, stump grinding and replanting boulevard ash trees would top $26 million. And that doesn’t count the tens of thousands of ash trees growing in parks and natural areas such as along the Mississippi River corridor. The Park Board felt fortunate this year to get an extra $500,000 in capital money from the city to help catch up with a backlog of stump grinding from diseased elms. It has to remove the stump to create the boulevard space to plant a new tree.
Even before the emerald ash borer hits, the city already has fallen behind on planting. For at least the last five years, public tree removal has outpaced planting, according to the Minneapolis Greenprint 2009 Environmental Report
The Park Board has planted on average 3,419 trees a year since 2003, but with the tree removals, there has been a net loss of 9,000 public trees during that time. And even if the Park Board replaced trees one for one, a new sapling doesn’t replace the lost tree canopy of an old, stately elm.
Because of diminishing federal funds, the Minnesota Department of Agriculture’s (MDA) ash borer management plan is likely to include fewer eradication projects, the Park Board BOARD estimates. Minnesota cities will probably need to address the bug invasion with limited local funds.
Ralph Sievert, the Park Board ‘sdirector of forestry, says that, just like the rest of the Park Board, his division is in “a hiring delay.” Of 51 total arborists positions, ten are vacant. That affects a lot of things, such as getting diseased elm trees removed. Those positions won’t get filled this year. The 2010 budget will hinge on state local government aid.
“We are not optimistic,” Sievert said.
How it spreads
Don Willeke is a veteran of battling tree disease. He led the charge in the 1970s for aggressive removal of diseased elms.
The emerald ash borer will prove more challenging, says Willeke, who also serves on the Minneapolis Tree Advisory Committee. For one, Dutch Elm disease kills trees more quickly and is easier to diagnose.
A bug is involved in spreading both tree diseases, he says. But with Dutch Elm disease, the bug transmits a fungal disease from tree to tree. With the emerald ash borer, the bug itself is the killer. It tunnels around under the tree’s bark and cuts off critical circulation, he says.
“The emerald ash borer could be killing one branch in an ash tree, if the tree is only lightly infected. The tree is still half alive,” Willeke says. “Whereas elms will go into collapse due to systemic infection of the fungus throughout its vascular system.”
Sievert says the Park Board has a much shorter learning curve to guide its polices. Dutch Elm disease arrived in the United States in the 1930s, he says. By the time it got to Minneapolis in the 1960s and 70s, policy makers had 30 years of research.
“We benefited from all the elm losses that happened on the east coast,” he says. The emerald ash borer arrived in 2002 in Detroit. “Now, Minnesota is part of the history-making of the emerald ash borer. It is such a new pest.”
According to Geir Friisoe, director of the plant protection division for the state, the typical sign of the emerald ash borer is crown dieback and woodpecker holes, cues that are not unique to an infestation. While the disease is hard to detect, the general public finds most infestations, not the traps or government surveys, he says.
People who suspect their trees have emerald borers should first make sure the suspect tree is indeed and ash, then call the Arrest the Pest phone line at 651-201-6684.
Recreation vs. urban forest
Willeke says the Park Board needs to reallocate resources to increase tree planting. He doesn’t agree it’s a money problem.
“By refusing to reallocate resources, they have made the decision against keeping the city green with this very pending threat,” he says. “In the 1970s, we planned ahead. We planted equal to or greater than our losses. Not doing that now is — the kind word is unwise. The actual word is … dumb.”
Park Board President Nordyke says he’s a friend of Willeke’s and understands his concern, but money is a problem. He calls it a difficult balancing act between spending limited resources on the urban forest, trails, recreation and a long list of deferred maintenance.
“When you have neighbors coming and talking to you about the fact that they have 2- and 3-year-old kids who can’t enjoy a summer day because the wading pool is broken, it is awfully hard for commissioners to vote to spend $3 million on trees,” Nordyke says.
Questions on the horizon
Some of the issues that are being investigated include tree removal policies and pesticide use.
The ash borer is most active in the summer but doesn’t travel far on its own. Sievert says the Park Board is not doing any ash tree trimming or tree removal from at least Memorial Day to Labor Day to reduce the risk on inadvertently spreading the bug. In addition to not moving firewood, the Park Board is telling residents not to do any ash pruning during the summer. Vreeland said the better the metro area does at limiting the spread will buy more time for the Northwoods.
Pesticides could save trees, or delay their loss, spreading out tree removal costs and avert a major loss of tree canopy in a short period of time. Sievert says Milwaukee already is injecting thousands of public ash trees, and the emerald ash borer is not as close to Milwaukee as it is to Minneapolis.
“We are still trying to make sure that is the right course to go,” he says. “They are spending like $800,000 just on doing that chemical treatment. You could plant a lot of trees for that amount of money.”
Useful web sites about the emerald ash borer
University of Minnesota Extension”:http://www.extension.umn.edu/issues/eab/
last revised: July 6, 2009