Fighting Emerald Ash Borer

The Streets and San tree trimmer's saw bites into the upper limbs of the large dead ash. Taking down a tree of this size safely is a big job. And this year there are more dead trees than ever lining Chicago's streets. The city's 580,000 trees took a double hit this year: the highly aggressive Emerald Ash Borer and last winter's hard freeze.

“When you look at effects of winter, that's a very good point,” said John Lough, senior forester for the City of Chicago. “We are noticing trees are definitely stressed; we had a lot of trees late to come out. Some trees didn't come out.”

The city's ash trees, already weakened by the Emerald Ash Borer beetle or EAB, were particularly hard hit by the winter's deep freeze. The EAB was first discovered in Illinois in 2006. It has spread quickly since then.

“Our ash population is approximately 80,000 trees on the streets. We imagine EAB pretty much in all of them.” Lough said.

--Graphic by Taurean Small

The small fluorescent green beetles fly into the ash canopy and begin munching on the leaves shortly after they emerge from the tree trunks. After mating, the females lay their eggs in the tree bark. It is the newly hatched larvae that cause the most damage to the tree. The larvae bore into the tree, leaving these telltale serpentine markings in the tree's conductive tissue that transports nutrients from the roots to the leaves. When this system is disturbed, the tree begins to die.

Up until last year the city's primary response to the EAB was to take the dead or dying ash trees down.

“We’ve removed around 10,000 ash trees, and this is going back from 2008. And that represents approximately 10 percent [to] 12 percent of our ash population.” Lough said.

Last year the Emanuel administration funded a new initiative to begin injecting an insecticide into 70,000 ash trees that could still be saved. Almost 38,000 ash trees were inoculated last year and 32,000 will be inoculated this year. The city is hoping to save, at worst three quarters, and at best, all of the 70,000 trees.

The city inoculates the trees with insecticide cleverly named TREE-age.

“We're putting TREE-age into the Xylem portion of the tree. If you remember from biology class, that's the part of the tree that the water is absorbed through the root system. It goes all the way up to the crown to all the leaves, and we use the same transport system. We put the TREE-age right there and within 24 hours, more or less, it’s throughout the entire tree.  [It’s] very effective.” Lough said.

The tree is inoculated for three years against the beetle. Tags are driven into the trees to prevent duplication.

Even with the early success of the EAB insecticide, there are still thousands of trees that need to come down. Lough says the bureau of forestry has cut down 7,000 trees this year and plans to cut 3,000 more by year's end.

“When we have a tree that we think may be in need of removal for whatever reason, typically we'll get a phone call from a resident or through a survey. We’ll have an inspector come out, (usually within seven to nine days) evaluate it, they’ll see if the tree needs to come out. Then we'll send a crew right out to take it.” Lough said.

But that's not the experience of 32nd Ward Ald. Scott Waguespack. He says the 32nd ward has 500 trees that are dead and need to come down and be replaced. He says he first reported this dead tree to the city four years ago.

“My staff and I work with our neighbors. We’ll take the pictures, sometimes send the pictures [and] keep a detailed list of which trees are dead and which ones need serious trims for emergencies, and constantly communicating that we need those lists taken care of through the Forester’s department.” Waguespack said.

But the bureau of forestry reports far different numbers. There are 119 tree removal requests in the 32nd ward according to the bureau, and 102 of those are scheduled for removal.  Lough said a big reason for the improved service is the new grid system.

“We've gone to a grid-based removal system where we’ll go into a ward in a particular grid blitz that grid.” Lough said. “We’ll deal with all the tree issues at that time and then move on to another grid in another ward.”

Waguespack says the grid has helped but hasn't cleared up his backlog of requests.

“I think it needs to be tweaked. I think there needs to be more crews out there and the grid needs to move a lot faster.” Waguespack said. “The emergency trees need to be handled either through a different crew and not wait for the grid to come around, and you’re talking very large branches from this past winter that trees died from or trees have been sitting there for quite a few years and are very dangerous to people.”

Dead trees are not only coming down along the city’s streets, they are also being cut down in the city’s parks as well. Also hard hit by the cold winter and the EAB, the park district has removed 2,500 trees so far this year. But the park district has decided not to inoculate its ash trees against the EAB.  The park district has far fewer ash trees than the city and says it will put its resources toward removal and replacement of ash trees rather than inoculation. The city sees the math differently.

 “For us it costs $46 a tree, which is fairly reasonable. When you look at inoculations versus the cost of removal and replacement, we’re talking more around $1,000 to remove and replace a tree.” Lough said. “So not only are we saving some of our Ash so we have the benefits of it [and] people can enjoy it, we’re also saving a little bit of money.”

Both the city and the park district say they have increased the number of replacement trees they are planting. New trees are planted in the spring and fall, and this year the city plans to put in 6,000 trees with the park district adding 2,500.