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University to remove, replace infested ash trees

July 16, 2013
Close-up showing the Emerald Ash Borer and the tunnels it makes in infected trees

Close-up showing the Emerald Ash Borer and the tunnels it makes in infected trees

The Illinois Department of Agriculture (IDA) has confirmed emerald ash borer infestation in many ash trees on the campus of Northern Illinois University, and as a result, plans have been made to remove infested and dying trees during the course of the summer.

Native to Asia, the emerald ash borer (EAB) is an exotic beetle that was unknown in North America until June 2002, when it was discovered as the cause for the decline of many ash trees in southeast Michigan and neighboring Windsor, Ontario, Canada.

EABs have since been found in several states from the east coast spanning across the Midwest, and in June 2006, EABs were discovered in Illinois. In a July 2006 declaration of nuisance, the IDA’s Bureau of Environmental Programs declared that all plants and trees infested with EABs be eradicated pursuant to the Insect Pest and Plant Disease Act.

The larvae of these small, metallic green pests feast on the trunks of ash trees, thereby cutting off their ability to transport nutrients and ultimately cause the tree’s decline. Ash trees can be infested with EAB for a few years before the tree begins to demonstrate any signs of EAB infestation. Symptoms of EAB include canopy dieback, D-shaped exit holes, shoots sprouting from the tree trunks and S-shaped larval galleries underneath the bark.

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Emerald ash borer infestation has caused the rapid decay of trees such as these located along the sidewalks between the library and Holmes Student Center.

EAB was first confirmed in Sycamore in July of 2009, and later in the City of DeKalb in June of 2011.  Since then, EAB- infested trees have appeared throughout DeKalb County. The severe drought conditions last year accelerated the rate of infestation.  As of today, 13 confirmed communities and countless other rural locations are impacted by the presence of EAB.

“Removal of weakened, stressed, infested, or otherwise undesirable ash trees is a proven management strategy.  If not infested already, these will be the first to become infested or go into severe decline, and will require the earliest attention,” advises Scott Schirmer, a plant & pesticide specialist supervisor and Emerald Ash Borer Program manager for the Illinois Department of Agriculture. “Removal and destruction of ash may not [per se] control the overall spread of the pest, but it reduces the potentially available host material required for the pest to complete it’s life cycle, therefore keeping populations and subsequent beetle pressure lower.  Removal of ash needs to be looked at in this manner, but also as a means to reduce risk and threat.”

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Infested ash trees pose a danger to pedestrians due to the brittle nature of the tree and the weakening of limbs caused by dry weather and EAB larvae.

Ash trees are naturally brittle, often among the first trees to structurally fail in severe weather.  EAB accelerates the decline process and increases the tree’s brittle condition.  By removing these ash trees, the risk and threat of them failing and causing serious harm or damage is mitigated. The recent and numerous EAB finds underscore the need for all communities—including higher education institutions–to be proactive against EAB, and the IDA has urged officials to initiate an ash-tree reduction-strategy.

“Begin by taking inventory of all ash trees within the community, budget needs for labor and equipment should large-scale ash tree removals be necessary. Then aggressively begin to cull your poor-conditioned ash trees,” says Warren Goetsch, Environmental Programs bureau chief.

As a proactive measure to limit the possible damage from an EAB infestation, Northern Illinois University began assessing; culling and removing stressed and damaged ash trees in 2012-13. This summer’s removal will include over 50 ash and other trees that are dead or dying.

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Trees such as this will be removed and replaced with hearty species immune to EAB infestation.

“Most of our ash trees are in various stages of decline,” says Jeff Daurer, associate vice president of Facilities Planning and Operations. “We are limiting the scope of tree removal and replacement to trees that are already 50 percent dead or greater. Then, during the fall planting season, our grounds crew will replant with hearty species that will thrive in this climate and are not affected by the ash borer.”

Members of the campus community wishing to report a tree that poses a danger may report it at NIU’s StaySafe website or via email at [email protected].

For more information about emerald ash borer infestation in Illinois and how to stop it, visit the Illinois Department of Agriculture website at