Emerald Ash Borer

 Insect Pest Attacks Ash Trees                                                  
                                                                                        
An exotic beetle from Asia was found feeding on ash trees in southeast Michigan in the summer of 2002.  Experts from Michigan State University identified the bug as Agrilus planipennis, or Emerald Ash Borer (EAB).  It is now abundant throughout lower Michigan, and has been identified from many locations elsewhere in the Midwest.  The Michigan Department of Agriculture has quarantined the entire lower peninsula in an effort to slow the spread of this destructive pest.

The beetle does most of its damage during its larval stage as it feeds under the bark of ash trees (Fraxinus species).  So far, it has not been observed feeding on any other varieties of trees or shrubs.  Infested trees exhibit dieback of the crown, with as much as 50% of the branches dying in one season.  Affected trees may also have vertical splits in the bark 2-4 inches long.  Often dense sprouting of shoots can be found arising from the trunk or roots.  Upon emergence, the adult beetles make "D"shaped exit holes through the bark.  Heavy woodpecker activity may indicate the presence of Emerald Ash Borer.

The beetle appears to have a one-year life cycle.  Adults emerge from late May through June and are present for most of the summer.  Eggs are laid on the bark, and newly hatched larvae bore under the bark to begin feeding.  The larvae remain under the bark until they pupate and emerge as adults the following year.

Control of the borer may be possible if it is identified before 10-20% of the crown has been affected.  Soil application of the systemic insecticide imidacloprid (available under several product names) in early spring, and insecticide sprays in June and July may be effective. Proper watering and fertilization along with proper mulching techniques are also important  Be sure to obtain the latest recommendations and follow all label directions before using any pesticide.  Some tree services offer emerald ash borer control.  Michigan State University Extension offers some information on frequently asked questions regarding the Emerald Ash Borer.

Forestry crews have already removed thousands of EAB-infested ash trees throughout Rochester Hills.  Ash trees on city-owned property are not treated for EAB because of the volume and the expense of annual insecticide treatments.  Replacement trees for the right-of-way may be purchased through the Cooperative Tree Planting Program.  Information regarding this program is located under Tree Planting.

Ash trees growing on private property are the responsibility of the property owner.  Those with infested trees need to have them removed before they become a hazard to their own property as well as adjacent properties e.g. streets, walkways, neighbors.  Information regarding removal of ash trees from private property can be found at the Michigan Department of Agriculture website.

Residents should also be aware that emerald ash borer may be transferred to new areas in firewood or other debris from infested trees.  Most of Michigan is currently under a quarantine that prohibits movement of ash trees or other infested materials, including logs and firewood, out of the area.  Please refer to the Michigan Department of Agriculture website for the most current information.

Additional information can be obtained from the following websites:

Michigan Department of Agriculture
U.S. Forest Service
Emerald Ash Borer Information

Anyone with questions or possible infested ash trees should contact the Forestry Division at 248-656-4673.