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The Emerald Ash Borer (EAB):

  • Is an insect that has the potential to destroy Metro Denver’s 1.45 million ash trees. It has already wreaked havoc in more than 25 states and parts of Canada, causing billions of dollars in damage.
  • Arrived in Boulder in 2013 and Broomfield in 2019. It’s only a matter of time before it arrives in Denver, if it hasn’t already. Unfortunately, it takes two to four years for signs of EAB infestation to manifest.
  • Has a limited flight range. It most commonly travels with humans who are transferring untreated ash tree firewood, chips larger than one inch, or nursery stock.
  • Eggs hatch and become worm-like larvae that tunnel through the tree’s water-conducting tissue just under the bark. The tunneling and feeding under the bark is what eventually kills the impacted tree.
  • Feasts on ash trees only, including the green (Fraxinus pennsylvanica) and white (Fraxinus americana) varieties, which are the most common in Denver.

Identifying EAB

How can you tell if your ash is infested by the EAB? Start by looking for these tell-tale signs:

Look for D-shaped exit holes

Look for larva

Wavy trail lines

Northern Flickers (type of woodpecker)

Crown dieback

Images courtesy Colorado State Forest Service