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By Vinde Wells
Editor
Two experts from the Illinois Department of Agriculture confirmed the presence of the emerald ash borer (EAB) in Oregon last week.
Street Superintendent Mike Bowers said Scott Schirmer and Jeremy Venhuizen found the insects infesting ash trees at Oregon Park East in the pine tree grove south of the ball diamond.
“This is the first EAB confirmation within the city limits of Oregon,” Bowers said.
Unless caught very early, the insect, a native of Asia, usually spells the death knell for ash trees.
The most significant damage to a tree by the emerald ash borer takes place when the insect is in its larval stage.
The larvae feed on the conductive tissue of the tree. This tissue is what transfers the nutrients and water from the roots to the leaves, and when this is disturbed, the tree begins to die.
In winter, the larvae relocate to the bark of the tree, effectively cutting off the tissue more. This ultimately results in the death of tree.
This can take place over a number of years, and the first noticeable sign is usually some die back in the crown of the tree. The tree will usually be dead by the following year or soon after.
To limit how fast the infestation can spread, the affected trees are usually cut down.
Oregon Park District Director Erin Folk said the trees infested at Park East were removed April 11 and 12.
Bowers said the discovery of EAB in the park means the beetles arrived between 3 and 5 years ago which indicates the number of ash trees showing signs of infestation will likely increase over time. “The first signs will appear in the canopy of the tree and spread downward,” he said.
The confirmation of EAB will increase the number of ash trees removed by the city each year, Bowers said.
“We have been removing about six trees a year since 2010 in anticipation of the EAB reaching Oregon,” he said. “We will begin removing 12-15 trees each year unless the infestation reaches high levels which will require even higher removal numbers.”
The city has about 100 ash trees remaining on the terraces.
Residents with ash trees in the terraces adjoining their properties have been notified and will be notified in advance of tree removal.
“The city pays for the removal and stump grinding of these ash trees and has established a cost sharing program for tree replacement for the residents affected,” Bowers said.
Bowers started following the EAB migration in 2009 and attended seminars on treatment options in 2010.
He reported to the city council in October of 2012 that although none had been detected, the pest could already be in the area.
He said then chemical treatments are available, but most have to be done every year throughout the lifetime of the tree.
Folk said the park district completed a tree inventory in 2011 and identified 75-100 ash trees on district property.
“As these ash trees become infected and removed the district will implement a tree replacement schedule to include trees that will be hearty enough to withstand the elements respective to northern Illinois,” she said.
The emerald ash borer was first detected in the U.S. in Michigan in 2002. It is believed to have arrived in shipping crates made of ash coming from Asia.
EAB was first found in Illinois in 2006 and has been identified by the Department of Agriculture in other Ogle county communities such as Stillman Valley, Byron, Davis Junction, Monroe Center, and Rochelle.