Our North American Ash trees are under attack.

To make matters worse, the Ash tree seems to have no known natural resistance to the attack. Stressed and weak trees - even healthy trees are susceptible.

Is it possible that North America could lose all of its Ash trees?

The culprit? The Emerald Ash Borer.

Beginning around 2002 infestations of the emerald ash borer were discovered in Michigan, Illinois, Indiana, Kentucky, Maryland, Minnesota, Missouri, New York, Ohio, Virginia, West Virginia, Wisconsin, as well as Ontario and Quebec. And, now in Pennsylvania.

Areas in green show where the borer have been found - so far.

The emerald ash borer originates from Asia - China, Japan, Korea and Russia. Not native to the United States, it likely arrived here in infested wood packing material on shipping cargo.

What can you do? Carefully monitor your Ash trees throughout the season.

Buy local firewood only. Don’t move firewood from one county to another. Campers are being advised to buy and use local wood only. Many areas are under quarantine. Chester County has not been quarantined. As yet, there have been no reported cases in Chester County. They are, however, not far to our west. Monitor diligently. Call right away if you think you see any of the signs or symptoms.

Early detection is essential.

What to look for? Die-back on the upper third of the tree, (the borer destroys the water and nutrient conducting tissues under the bark), suckering at the trunk, D-shaped exit holes in the bark where adults emerge, vertical splits in the bark, and s-shaped tunnels beneath the bark in the cambium, where larvae virtually stop food and water movement, starving the tree to death. An increase in woodpecker activity.

It could take 1-3 years for an infested tree to die.

The adults begin to emerge mid to late May and peak by late June. Females will begin laying their eggs about 2 weeks later. In about 2 weeks the eggs hatch. The larvae will then bore through the bark, burrowing into the cambium (the area between the bark and the wood). Nutrient levels are high there and the larvae feed for several weeks. They over-winter in the outer bark or within the outer inch of wood. The adults can fly ½ mile or more from the tree where they emerge. When they emerge, they leave a "D" shaped exit hole in the bark (roughly 1/8 inch diameter). Exit holes may be difficult to see because of their size. A look under the bark will reveal the s-shaped tunnels made by the larvae. The adult ash borer has a 1 to 2 year life cycle.


Insecticide treatment on trees having low to moderate crown dieback (less than 20% - 40%) may save the infested tree. Healthy trees that show little or no crown dieback may be more optimistic. Monitor diligently. As yet, there have been no reported cases in Chester County.

R. Chris Williamson, Ph.D., and Fredric Miller, Ph.D. of TCIA (Tree Care Industry Association): “Research and experience has shown that insecticides can protect ash trees from being killed by EAB. However, success of insecticides is not guaranteed!”

Treatments may be more effective if the health of the tree is maintained. Fertilization in fall or spring is recommended, along with watering regularly especially during drought periods. Keep your trees in good health.

More research?

Emerald Ash Borer Photos

Time Line of EAB Detection in Pa

More EAB Photos

Penn State fact sheet

Pa Dept of Agriculture fact sheet

Penn State Tree Identification fact sheet

Penn State EAB information

Pa DCNR fact sheet

Pa Dept of Agriculture Quarantine Map

Pa Forestry Information

Pa Forestry Leaflet

Back to Tree Health & Telltale Signs

To Scruggstree Home Page

The Emerald Ash Borer

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