Bug Alert: The Destructive Pest Knocking on Washington’s Door

There is a major threat looming for Washington’s canopy, and it comes in the form of a tiny, metallic-green beetle. Meet the Emerald Ash Borer (EAB) an invasive wood-boring pest responsible for destroying hundreds of millions of ash trees across North America.  

While historically an East Coast crisis, EAB has officially breached the Pacific Northwest, with recent confirmed infestations in neighboring Oregon and British Columbia. It is no longer a matter of if it arrives in Washington, but when.  

Female and Male Emerald Ash Borers

The Eye-Opening Reality

The adult beetles cause minimal damage just chewing on leaves. The real killers are the larvae.  

Once eggs hatch on the bark, the larvae chew deep into the wood, carving winding, S-shaped tunnels (galleries) directly through the cambium layer, the tree's vital vascular highway. By disrupting this network, the larvae effectively strangle the tree from the inside out, cutting off all water and nutrients.  

Experts warn that Washington could experience near to total mortality of its ash trees within 10 years of an unmanaged infestation. This threatens both native Oregon Ash in delicate wetlands and the green or white ash trees lining neighborhood streets.  

Traces of Emerald Ash Borer on the Trunk of a Tree

Red Flags to Watch For:

• D-Shaped Exit Holes: When adult beetles emerge from the trunk in late spring, they leave distinct, perfectly D-shaped holes about 1/8 inch wide in the bark.  

  
  

• Top-Down Dieback: The tree's crown will rapidly thin and lose leaves, dying from the top down.  

  
  

• Epicormic Sprouts: Stressed trees will desperately grow dense clusters of new branches or "suckers" directly out of the lower trunk or base.  

  
  

How You Can Help?: Never move firewood! EAB spreads rapidly when people unknowingly transport infested wood across county or state lines. Always buy firewood where you plan to burn it.  

Early detection is our absolute best weapon to protect local canopies. If you notice these symptoms on an ash tree, take photos and report them directly to the Washington Invasive Species Council to help slow the spread.