Oak Creek fights its emerald enemy

Ash borer can't be stopped, but it can be strategically slowed

July 16, 2012

Oak Creek - Loss of leaves, splitting bark, and the death of over a thousand ash trees await the cities where the emerald ash borer is present.

Oak Creek - along with Milwaukee, Franklin and many others throughout the Midwest - is one of these cities, all of which have shifted their fight from preventing the killer beetle's arrival to offsetting at least some the resulting destruction after it's found.

Meet the unwelcome guest

The emerald ash borer is a metallic green beetle, about half-inch long and one-eighth-inch wide. Its larvae feed on the inner bark of ash trees, prohibiting the tree's ability to move water and sap throughout it and eventually killing it. The beetle's typical life span can range from one to two years.

The beetles are 100 percent fatal to ash trees. Untreated trees hit with the parasite can die within two to four years of infestation, officials say.

Infested wood transported by people is one of the main ways the beetle has traveled to new areas. The beetle on its own can only fly a short distance.

"It would be optimal if residents kept their wood on their property," noted Oak Creek urban forester Rebecca Lane. "There is no good reason to move wood back and forth with so many different insects and diseases waiting to pounce."

Slowing the borer

The beetle's presence in Oak Creek isn't news. It was found locally more than two years ago.

"Oak Creek was one of the first places in Wisconsin to see this parasite," Lane said.

"(The emerald ash borer) can be found in all corners of Oak Creek," she said. "The population of the insect is definitely high."

Today, there are still approximately 2,500 ash trees in Oak Creek, not including those in wooded areas and private lots, Lane said. Each of those is in danger.

Lane said it is not possible to stop the emerald ash borer completely, but there are ways to slow it. To that end, Oak Creek has been working tirelessly to treat the ash trees while employing other strategies.

"We have a variable program where we do a mixture of treatment to the trees and then some removal," she said.

For the city, the cost to treating ash trees is expensive - about $1.25 per inch - but it's a cost she feels is justified in an attempt to save the community's urban canopy population.

"(Experts) are finding out that having trees treated is beneficial to the untreated trees near them," Lane said. "These treatments are helping everyone's ash trees."

Treatments include trunk sprays, trunk injections and soil insecticide treatments. Three of the most widely used chemicals in the insecticide products for treating the emerald ash borer are imidacloprid, dinotefuron and emamectin benzoate.

To help pay for those treatments, Lane said, Oak Creek has received three related DNR Urban Forestry grants in the past three years, amounting to approximately $50,000.

A Legacy approach

Oak Creek's partner is its efforts is a company that has tried to educate the public as well as present treatments options to both government units and private landowners.

This is the third year on a five-year commitment plan that Oak Creek has with the Legacy Tree Project, launched in 2010 by Valent Professional Products, a private crop protection firm serving the agricultural and non-crop products markets in North America.

LTP is treating about 125 Oak Creek ash trees for the emerald ash borer by using an insecticide product called Safari. Another 700 are under treatment with contractors.

"The soil injection of Safari is taken up by tree roots and translocated via a tree's sap and water conductive tissue," Lane said. "It moves to whatever areas it can reach in a tree, and as the chemical comes into contact with the larva, the larva dies."

The Legacy Tree Project will save the city approximately $35,000 over the course of its commitment, Lane said. LTP's treatment is free to the city.

Lost trees, hoped-for gains

Removal and replacement of trees can also be a form of treatment.

As part of the control effort, about 3,000 public trees have been removed along roads on streets and in rural areas, parks, and other municipal lands so far.

"To best manage the work load and to kill as many of the insects as possible, we are currently treating many trees that are not worthy of long-term treatment," Lane said. "Eventually, all but a few high quality ash trees will be removed."

Lane said that these treatments will be done in stages unless things get out of hand and the city has to clear-cut the trees for safety.

"It is estimated that one in every five urban trees is an ash, so that is going to be a devastation to Wisconsin and the Midwest," Lane said. "We really hope people will plant many trees in place of the removed ashes."

Trees that are planted in place of the ash are maple, Ohio buckeye, ginkgo, oak, honeylocust, sycamore and hedge, among others.

In fact, Lane said the best defense for maintaining Oak Creek's urban canopy against the emerald ash borer and other insects and pathogens is to diversify.

"Our goal is no more than 10 percent of one genus for the trees that the city maintains," Lane said. "It is not an easy goal to achieve. Residents should diversify, too, because private trees make up the greater percentage of the Oak Creek tree canopy."

The ash borer elswhere

The emerald ash borer was detected in Wisconsin in November 2009. Because the beetle typically will not show up for a year or two, core samples from the trees concluded that pest could have been active in Wisconsin five years prior, Lane said.

The emerald ash borer has been found in 12 Wisconsin counties: Rock, Vernon, Racine, Ozaukee, Milwaukee, Brown, Kenosha, Walworth, La Crosse, Crawford, Washington, and Waukesha.

Wisconsin ceased the planting of ash trees in 2001 and began culling out the worst of the trees because of the threat.

How to help:

Do not move firewood. Transporting the wood moves the beetle's eggs and larvae along with it, thus allowing them to spread the disease further.

Burn wood where you buy it. This also helps EAB from spreading to other campsites or locations.

Check your ash trees for signs of infestation. Signs include loss of leaves, sprouts from roots and trunk, splitting bark, woodpecker activity, S-shaped galleries under the bark and small D-shaped exit holes.

Report anything of concern. If you have questions about EAB or see symptoms of it on a tree, contact a certified arborist.

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