Emerald Ash Borer

Agrilus planipennis, the emerald ash borer (EAB), is a small metallic green beetle, about 1/2” long and 1/8” wide. Insects will typically attack stressed or weakened trees first, before moving on to healthy specimens. Not the case with EAB. EAB will feed equally upon healthy, well-maintained ash trees or weakened, stressed trees.

First identified in Michigan in 2002, EAB is present in all of northern Illinois, and has been observed only on ash trees. Ash trees are in the olive family, and include blue, European, green, white and ‘Hessei’ ash. The European mountain ash is part of the rose family, and is not a host of EAB.

Signs and Symptoms

• Infestation can be difficult to detect until tree canopy dieback begins.
  
  
• Watch for epicormic branching – shoots coming up from the base of the tree.
  
  
• Check for lateral bark slits.
  
  
• Look for d-shaped emergence holes in the trunk or limbs. Can be difficult to see.
  
  
• June is the best month to assess tree canopy on an ash. Watch for adult feeding activity-notch like pieces missing from edges of leaves.

Conditions

• Adult beetles active, laying eggs May thru August.
  
  
• Larvae hatch and chew into inner bark and feed on phloem tissue, cutting flow of water, nutrients. Results in tree dieback and decline, eventual death of tree.
  
  
• Emerging adult beetle begins entire life cycle again.
  
  
• An infected tree will be repeatedly infested until it dies.

Management

• Removal is not always necessary; infested trees can be treated if symptoms are slight.
  
  
• Merit (imidacloprid) soil injections at intervals around the base of the tree offer control. Annual treatments are necessary for several years, and when imidacloprid sufficiently builds up in the tree, injections may be done every other year.
  
  
• Wedgel injections directly into the trunk of the tree may be used solely or in combination with soil injections. Wedgel injections begin after leaf emergence in the spring, continuing thru the summer

There is a wealth of information available on the internet. Go to www.emeraldashborer.info and you may research many aspects of this invasive insect. An excellent summary for homeowners is the Emerald Ash Borer Insecticidal Management Entomology Fact Sheet NHE-163 prepared by Philip L. Nixon, a former extension entomologist at the University of Illinois/Urbana. This fact sheet can be found at the Morton Arboretum web site, www.mortonarb.org.

Also check the web site www.treeresearch.org to learn about Dr. Dave Roberts, with Michigan State University, as he describes his experiences with EAB from discovery through successful control of EAB, both preventively and curatively, in residential, commercial and municipal environments.

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