LONGMONT, Colo. — The emerald ash borer threat has spread to Longmont, the only infestation known outside of Boulder.

“Approximately 15 percent of the trees that make up Colorado’s urban forest are ash,” the Department of Agriculture said. “There are an estimated 98,000 in the city of Boulder alone. The Denver metro area has an estimated 1.45 million ash trees. EAB is responsible for the death of millions of ash trees in the United States.”

With the spread of the insects, you might be concerned about your trees. First, identify if you have ash trees by the following characteristics from the Colorado State Forest Service.

• Branches and buds grow in pairs, directly opposite from each other.

• Multiple leaves, typically five to nine, occur on a leaf stalk.

• The paddle-shaped leaves are smooth to “finely toothed” along the edge.

• Mature trees’ bark looks like diamond-shaped ridges.

You can identify the signs of infestation if you notice:

• Fewer leaves or branches in the upper part of the tree.
• D-Shaped holes, 1/8 of an inch wide.

• Vertical splits in the bark and/or winding S-shaped tunnels under the bark.

• Increased woodpecker activity at the tree.

“It’s the most destructive pest in all of North American history,” said Kelly Gouge of Swingle Lawn Care.

Emerald ash borer are a breed of tiny insects found slowly killing ash trees.

“Untreated trees will die, it’s as simple as that,” Gouge said.

Longmont tree experts said it was just a matter of time until the insect spread. Emerald ash borer was first confirmed in Boulder in 2013.

“It’s disappointing because now we know what’s ahead. But to know that it’s close by we can actually start treatments,” Longmont City Forester Ken Wickalund said.

The beetles can spread quickly, tunneling themselves inside the tree trunks, eating tissue and preventing water flow.

Longmont city foresters have been preemptively removing low-quality ash trees to prevent the spread. But now they can zero in on treating 900 of the 2,800 trees.

“But the fact that we found it means it’s been here for three to four years already,” Wickalund said.

The insect can migrate or travel through firewood. Boulder County has a strict law against taking wood across county lines. But Colorado homeowners should take their own precautions.

“Treat it and protect that tree, or allow it to die and cut it down,” Gouge said.

Experts recommend chemical treatments such as soul or trunk injections. Millions of ash trees across the country are plagued with the insects.