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City trees under attack
Officials are asking residents to watch spruce trees and help control the spread of the Ips beetle.

By Jennifer Frazer

MICHAEL SMITH/WTE This piece of bark from a spruce tree at Olivet Cemetery in Cheyenne depicts the tunnels bored by Ips beetle larvae. The eggs are laid in the main tunnels, and the larvae branch outward to feed.

rep8@wyomingnews.com

CHEYENNE - Spruce trees around town are succumbing to a tiny black beetle called Ips, alarming city foresters.

Officials are asking residents - some by letter in the cases of very sick trees - to watch them and, if they have reached the point of no return, to cut them and carefully dispose of the wood to prevent further spreading the voracious pests.

Ips beetles are native to the forests of the Rockies, and the species currently wreaking havoc here prefers spruce, a type of short-needled conifer.

At the Olivet Cemetery on Pershing Boulevard, where half of the 1,200 trees are spruce, there is a plentiful food supply.

There, 10 trees were removed in July due to beetle infestation, and another 12, thinning and brown, will follow soon, said Randy Overstreet, assistant director of Cheyenne Urban Forestry.

Things have gotten so bad that city crews sprayed the trunks of trees bordering Pershing on Monday and Tuesday night and soon will cover trees throughout the cemetery.

Some of the felled trees were upwards of 80 years old, but nothing but dusty stumps are left.

Overstreet estimates that there are probably 100 privately owned spruce trees throughout Cheyenne that also are currently infested, about 10 percent of the city's spruce population.

"It's not a high number," Overstreet said, "but it could be very high next year."

The beetles cause destruction by burrowing under the bark, where they lay their eggs.

When the eggs hatch, the larvae feed on the layer of tissue between the bark and the wood where most of the tree's nutrients are transported.

When the beetles consume enough of this tissue, the tree dies. They then exit through pin-prick-sized round holes scattered in the bark.

Because the beetles can produce three generations in a single summer, their numbers can grow rapidly.

Healthy trees have systems for fending off attack, but drought-stressed trees - as many in Cheyenne are - have a hard time defending themselves. After six years of drought or near-drought conditions, a previous winter with little precipitation and strong, drying winds, many local spruce are losing the battle.

And unfortunately, the oldest and most stately trees are typically the most vulnerable to infestation, Overstreet said.

The tops of trees are the first part to turn brown, but the discoloration soon progresses down the tree, sometimes in a matter of days or weeks.

The beetles began stirring up trouble about 10 years ago in Denver, Overstreet said, and have gradually moved up the Front Range.

Because the tiny beetles - only an eighth of an inch long - can only travel about a mile at most in their lifetimes, Bob Lee, director of environmental management, and Overstreet suspect firewood haulers of unwittingly importing the pest from forests.

In order to prevent unwanted hitchhikers, they advise waiting until a dead tree has lost its needles and is starting to lose its bark before harvesting.

Ips beetle outbreaks also are tricky to manage because symptoms of a beetle infestation are hard to detect until it's nearly too late.

"The problem is, the beetle could be in the tree and you would never know it," Overstreet said.

The sawdust produced by burrowing beetles often is blown away by stiff Cheyenne winds. And though trees can produce nodules of sap at the entrance of bark beetle tunnels, because the insects begin their attack so high in the tree, people cannot see them from the ground.

Overstreet suggests that homeowners who are concerned about their trees check to see if the tops are dying. If so, he added, they should consider contacting a licensed tree service to evaluate the extent of the problem and find a course of action.

For any spruce owner, winter watering is crucial to helping prevent attack, Overstreet said.

Choose a warm, calm winter day and soak the tree from the tips of the widest branches outward about once a month. Watering under the tree weakens the ground and does not adequately provide water.

Cheyenne Botanic Gardens Director Shane Smith agreed that winter watering is vital, and extra water in xeriscaped or rock-scaped lawn is important too.

Spraying is an option for trees in infested neighborhoods that aren't yet showing signs of disease, he said.

But homeowners also can employ a Plan B: plant small trees underneath the large ones, so when their time comes for whatever reason, a replacement is ready.

Replacements or no, Smith said he is sorry to see spruce go.

"The other big tall tree in our town (besides the cottonwood) is the spruce," he said. "We hate to lose those guys because they really are the ones that get some height, block some wind and do some good things."