Emerald Ash Borer: The Silent Killer Spreading Across America

The Growing Threat of Emerald Ash Borer

The emerald ash borer (Agrilus planipennis), commonly known as EAB, is one of the most destructive forest pests ever to reach North American shores. Originally from East Asia, this metallic green beetle was first detected near Detroit, Michigan in 2002. Since then, it has spread to more than 35 states and killed hundreds of millions of ash trees.

How to Identify Emerald Ash Borer

Identifying EAB early is critical to saving your ash trees. Use our tree identification tool to confirm your tree species, then look for these key signs:

• D-shaped exit holes in the bark, roughly 1/8 inch wide
• S-shaped tunneling patterns (galleries) beneath the bark
• Crown dieback starting at the top of the tree and progressing downward
• Bark splitting that reveals serpentine galleries underneath
• Increased woodpecker activity as birds feed on larvae beneath bark
• Epicormic sprouting (new shoots growing from the trunk or main branches)

The adult beetle is about half an inch long with a bright metallic green body. Larvae are creamy white, legless, and found beneath the bark in distinctive winding galleries.

Why EAB Is So Devastating

EAB larvae feed on the inner bark and cambium layer, disrupting the tree's ability to transport water and nutrients. An untreated ash tree typically dies within 2-4 years of infestation. Because symptoms often do not appear until the population is well established, many trees are beyond saving by the time the infestation is noticed.

All North American ash species are susceptible, including green ash, white ash, black ash, and blue ash. This means roughly 8 billion ash trees across the continent are at risk.

Treatment and Prevention Options

If EAB has been detected within 15 miles of your property, preventive treatment is recommended:

• Trunk injections with emamectin benzoate provide 2-3 years of protection and are the most effective option
• Soil drenches with imidacloprid can protect smaller trees
• Bark sprays offer seasonal protection but require annual reapplication
• Biological control agents, including parasitoid wasps from Asia, are being released by USDA in some areas

Treatment is most effective when started before the tree has lost more than 50% of its canopy. Trees with significant dieback are generally not candidates for recovery.

What You Can Do

The most important step homeowners can take is to avoid moving firewood. EAB spreads naturally at about 10 miles per year, but human transport of infested wood can carry it hundreds of miles in a single trip. Buy firewood locally and burn it where you buy it.

Contact an ISA Certified Arborist for a professional assessment of your ash trees and to discuss treatment options specific to your situation. You can also diagnose symptoms using our online tool.