Cheyenne Botanic Gardens

Cheyenne Urban Forestry officials are bracing for the arrival of an insect City Forester Mark Ellison calls ''the most destructive forest pest we have seen in the United States."

Ellison is referring to the emerald ash borer, a roughly inch-long insect that has killed tens of millions of ash trees in this country since it's arrival from northwest Asia. Ellison said Wednesday that while the ash borer has not been found in Cheyenne so far, it has been identified in nearby Longmont, Colo., in addition to Nebraska and South Dakota.

Ellison said ash trees in Cheyenne are especially vulnerable because they have already been attacked by a variety of other insects and diseases in recent years. He recommended private owners of ash trees take a look at the condition of their trees now and says they may want to consider cutting them down if they are not in good condition.

Ellison said he thinks the city will end up cutting down over half of the ash trees on public property. For trees that are in better condition, he said arborists can inject a treatment that may be effective in helping healthier trees resist the insect. There are also over the counter treatments that are available, which while not as effective as those administered by arborists, can sometimes help a healthy tree fight off the insect. Cheyenne is currently conducting an inventory of ash trees on private property to get a better idea of the number and condition of those trees.

Ellison said that while Cheyenne is at the most immediate risk from the ash borer, other Wyoming communities also face a longer-term threat. He named Casper and Powell as two cities with large ash tree populations that may face a big threat from the insect.