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EAB threatens local ash trees

By Ben Rodgers

ASHWAUBENON – The larvae of a bug small enough to sit on a fingernail is destroying ash trees in the state and won’t stop until the trees are dead.

The emerald ash borer (EAB) is an invasive species that was first discovered in Michigan in 2002.

Since then it has spread to 30 states, including 48 of 72 counties in Wisconsin.

In response to the spread of EAB, the Wisconsin Department of Agriculture, Trade and Consumer Protection has initiated a statewide quarantine for moving firewood that went into effect March 30.

“They’ve been quarantining areas by county based upon the finds, and it’s gotten to the point where the majority of the counties are quarantined so they just quarantined the whole state,” said Tim Bauknecht, Ashwaubenon village forester. “Which in essence relaxes restrictions, but it still makes sense to limit the spread of any type of firewood.”

Currently ash trees make up about 14 percent of all trees in village parks and on boulevards. Five years ago that number was closer to 20 percent.

“We’re not going to do anything to promote the spread by transporting firewood and logs,” Bauknecht said. “We’re going to try and do what we can to try and minimize the spread, but basically we’re at the point here now where we need to manage a large amount of trees that are going to die in the next five to 10 years.”

EAB was found in Ashwaubenon in January 2017 in a localized location near Marvelle and Fox Heights lanes. Then this winter village staff discovered 15 more locations.

“The exit holes are very difficult to find, they’re super tiny, they’re 1/8 of an inch across. So the easiest way we’re finding new EAB infestations are the flecking or the removal of bark from woodpecker activity trying to get the larvae,” Bauknecht said. “If you see woodpecker activity, not necessarily the birds themselves, but the flecking of bark on ash trees that’s a possible indicator that you got EAB. That’s how we’re finding the majority of our new finds.”

The larvae are the problem. They burrow under the bark and essentially cut off the path for the tree to distribute nutrients. Ash trees die from the inside out.

The larvae of the emerald ash borer are what kills ash trees. This is what an infected tree looks like beneath the bark after the larvae move through and cut off the supply of nutrients the trees need to live.
Photo Courtesy of Bugwood.org

Because of this, EAB moves slow and often takes about five to seven years to kill off a tree.

In addition to harvesting ash trees and replacing them with different species, Ashwaubenon also deployed three different varieties of stingless parasitic wasps.

The Oobius, Tetrastichus and Spathius are wasp varieties produced in a Michigan lab overseen by the Animal Plant Health Inspection Service of the U.S. Department of Agriculture.

“These wasps have been thoroughly tested, extensively tested, to make sure they’re not going to utilize any of our other native specifics we have here,” said Linda Williams, forest health specialist for Northeast Wisconsin with the Department of Natural Resources. “These three parasitic wasps are very specific to EAB. If they don’t have EAB, they die.”

Green Bay has also deployed the wasps, as well a park in Door County and areas in Southeastern Wisconsin. The wasps infect the eggs and stop the spread.

However, the wasps aren’t going to stop the spread entirely, they instead make the future easier for ash trees in the region.

“It’s not necessarily going to save the trees that we’re looking at today,” Williams said. “It’s a long-term management option.”

Once EAB moves through the region and kills a majority of ash trees, new ash trees will start to grow and those are the ones Williams said the wasps will help protect by eradicating EAB.

“You have to have EAB to release these and you have to have enough of them to release them, otherwise they die,” she said.

One area where there are more ash trees than Ashwaubenon is Barkhausen Waterfowl Preserve in Suamico.

“The slower we can stop the spread of this thing, the more chance we can get for people to research and find a way to combat them,” said Jason Petrella, program and natural resource coordinator at Barkhausen.

Brown County forests are made up of roughly 24 percent of ash trees.

The county hasn’t deployed wasps yet, but is currently looking at diversifying tree populations moving forward.

“The big thing now is to really think about diversifying the tree population,” Petrella said. “Don’t plant ash.”

Steve Kaufman, DNR service forester for Brown County, said there are wetland areas of Suamico that are a concern because they contain roughly 90 percent ash.

“That’s where we find the high percentage of ash,” Kaufman said. “In the upland areas ash is generally a smaller component, so when it dies, the forest does not change that much and other trees replace it. But in wet sites we don’t have that luxury.”

Some areas will be too hard to reach and replant so the landscape would eventually naturally convert to grassland or brush, he said.

“Oftentimes people think it (EAB) won’t kill the all the ash, but it will eat all of it, and they’ve adapted to our cold winters,” Kaufman said. “A very cold winter will kill some of them but not all of them.”

EAB has not been confirmed in Suamico yet, but the county is still taking proactive measures.

Homeowners with ash trees have a few different options. If their village has a full-time forester, they can call and see if that person could come out and inspect a suspect tree.

“They can also contact the UW-Extension Office to get help to diagnose,” said Vijai Pandian, horticulture educator with the extension service. “If the homeowner feels this tree is so valuable to them and it’s still looking in particularly good condition, we encourage homeowners to go to EAB treatments.”

There are also applications and injections a licensed commercial arborist could complete to save trees at different stages in their lives.

However, Pandian said the easiest way to avoid EAB is to follow the lead of the county and DNR and plant something else.

“It’s absolutely essential,” he said. “It looks like we did not learn the lesson when Dutch Elm Disease came in and wiped out the native elm (in the 1960s). Now we are paying the price for that. So we are encouraging people to look for other species of trees.”

Even though the Wisconsin Department of Agriculture, Trade and Consumer Protection has essentially relaxed county quarantines by the implementation of a statewide firewood transportation ban, Pandian still recommends people buy firewood locally.

“We still encourage people not to move their firewood from one county to another county,” he said. “We just want to try and minimize the spread as much as we can and slow down the spread as much as we can.”

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