EAB Biology and ID

What it Does

EAB is a metallic wood boring beetle.  EAB larvae feed under the bark and into the wood of Ash trees. The feeding disrupts the tissues that transport food and water within the tree and causes the tree to die.  The feeding also weakens the structure of the tree.  The tree will sometimes send out epicormic shoots (secondary growth) from the trunk.





Larvae hatch from eggs in July and burrow through the bark and into the cambium layer of the tree.  They form S-shaped galleries under the bark, 4-20 inches long.  The galleries are filled with frass from the larvae’s feeding. The feeding results in girdling of the tree and disrupts the movement of food and water within the tree. Larvae live for 1-2 years and undergo 4 instars; they overwinter in the outer sapwood of the tree.  

The larvae are white, flattened, and segmented.



In early spring, the overwintering larvae begin to pupate. This stage lasts about 28 days.


Adults emerge from D-shaped holes in the bark in May through June.  Adults feed on the foliage.  The females begin to lay their eggs in mid-July on the bark of the Ash trees.  Each female may lay up to 75 eggs.  Males live about 13 days and females live about 21-25 days.  

Adults are iridescent green, 1/2 inch long and 1/8 inch wide.




Eggs hatch within 7-10 days and the newly emerged larvae begin to burrow into the bark.  They are small, brownish and laid singly or in groups.

EAB Lookalikes

EAB Quick Guide PDF


About Ash

Ash trees are not native to Colorado.  They have been planted as ornamentals throughout our urban areas. Ash comprise approximately 15% of our urban forest.  Within Jeffco, they are found at our lower elevations in landscaped areas.

Ash ID

  • True Ash are in the genus Fraxinus
  • Ash leaves, buds, twigs, and branches are arranged opposite each other
  • Leaves are divided into 5-10 pairs of leaflets
  • Leaf edges are mainly smooth to slightly toothed
  • Ash leaves turn color and then drop in the fall
  • Bark on older trees is grayish with diamond-shaped fissures