With their graceful, arching boughs and robust leaves, ash trees are a wonderful feature of the Denver metro landscape. Of the city’s trees, 1 in 6 is an ash.

Sadly, that number is expected to diminish dramatically in coming years. Experts predict that the trees will soon be under assault from a destructive, metallic green beetle called “the emerald ash borer.” The ash borer lays its eggs on the bark of the ash tree. Once the eggs hatch, larvae begin to feed under the bark, creating channels that eventually kill the tree.

Non-native to America, the ash borer was first seen in Nebraska in 2002 and has since been found in Boulder and Longmont. They are expected to soon migrate to Denver.

If you have an ash tree, experts suggest two options: Consider removing it now and replacing it with a different species of tree. Or explore treatment options, should the tree end up with emerald ash borers.

Here are the symptoms to watch for:

• The tree canopy begins to thin or die, as nutrients and water are no longer able to reach the top.

• New branches sprout from the trunk’s lower base.

• Woodpeckers are attracted to the tree as they look to feast on the beetles.

• Vertical fissures on the bark appear and serpentine pathways made by the larvae can be seen just beneath the bark.

If you notice these changes in your ash tree, contact an arborist to discuss your options. Experts disagree on the effectiveness of various treatments designed to save ash trees, so be sure and get several opinions before acting.