Bugs That Kill Colorado Trees | Front Range Arborists

Bugs That Kill Colorado Trees

To those of us living in Colorado, a constant threat to the health of our trees is the risk of pest infestation.

Many species of trees are susceptible to damage from an assortment of bugs. Dead or damaged trees from bug infestation are not merely an aesthetic blight, but can also present a threat of fire.

As you might expect, the warmer months of spring and summer are generally the period of greatest bug activity, beginning as early as February, in some cases. When temps are high, tree sap is flowing and leaves and fruits are in full bloom; these are all attractants to tree-killing bugs. The recent epidemic of pine beetles is a prime example of what devastation a bug can wreak on tree populations. Millions of lodgepole pine trees were lost to the mountain pine beetle over a span of 20 years.

Identifying the Bug and Its Damage

To keep your trees and shrubs protected from these threats, it is important to know what to look for, when your trees are most vulnerable and how to treat them. Here are some of the bugs that pose a threat to your Colorado trees, and how to know when they are active in your vegetation:

Crown Borer –

This bug favors fruit trees such as plum and peach. Most active during the months of April through July, their impact on your fruit trees can be spotted by tree sap or frass, resembling sawdust. When the crown borer is active, the tree will ooze sap. Stressed trees are more susceptible to the crown borer, so proper pruning and watering will help prevent them.

Bronze Birch Borer

– Another wood-boring bug, the larval stage of this beetle can readily destroy birch trees. Look for signs like small exit holes left in the bark of your birch tree. The Bronze Birch Borer larva are active April through July. Plant trees in cooler areas, keep watered and use mulch to keep soil at base of tree cooler.

Poplar Borer –

Working primarily through the summer months, this bug will bore through the bark of poplar, cottonwood or aspen trees. Damage is in the form of drill-like holes with blackish stains in the bark, and frass or shavings at the base of tree. Weakened trees are most susceptible to attack, so proper care is the best prevention. Insecticides are effective during egg-hatching cycles.

Elm Bark Beetles –

Affecting American and English elm tree species, they are known to carry Dutch elm disease, destroying tree tissue under the bark. Boring dust can be found at the base of the affected tree. Trees with Dutch Elm disease should be removed and healthy trees kept watered, as a preventative.

Lilac/Ash Borer –

Larvae of this species bore tunnels into the trunk and branches of ash trees. Damage will typically be focused in the lower trunk and can be identified as drill-like holes approximately 1/4 -inch in diameter, with sawdust present. Activity can be found from April to May. Trees most susceptible to these bugs are recent transplants or stressed trees.

Tussock Moth Caterpillar –

The black-tusked tussock moth caterpillar is responsible for the recent devastation of over 25,000 acres of fir trees. This species can quickly defoliate an entire forest of Douglas firs. They are most active from May through June. Defoliation most commonly begins at the top of the impacted tree. Signs include eggs and pupae in the bark. Treatment requires application of pesticides, such as permethrin.

Ips Beetles –

Ips, or engraver, beetles attack spruce and pine trees beneath the bark, creating tunnels that can kill an affected tree. The engraver beetle is active from February through September. Most commonly, its targets will be weak or stressed trees. Drought conditions can also make your trees more attractive to the IPS beetle, so prevention is primarily comprised of routine maintenance, such as pruning, watering, tree spraying, etc.

Call the Colorado Tree Experts for Help

The best overall care program for preventing bugs from destroying your trees is a combination of pruning, watering and targeted pest control. Front Range Arborists is a privately owned and locally operated tree and shrub service, offering a full line of services that will protect your vegetation and keep it healthy.

Contact us today for a consultation on the ideal approach to your vegetation requirements. Our expert arborists will provide a detailed description of the services we offer and a free estimate. We understand what your trees and landscaping mean to you, and we know how to keep them healthy. Let our certified team of tree and shrub professionals work for you.


Find out more about how Front Range Arborists can help provide services to residential, commercial, and municipal institutions with all of our Tree Services: