Tree Diseases and Insect Pests#

Urban environments are extremely hostile places for shade trees to grow and survive because there are many interrelated variables that may cause urban shade tree stress. Stress may be defined as any environmental pressure that causes a change in a tree's physiology that predisposes the tree to invasion by secondary organisms (disease & insects) that it would otherwise resist.  

Some of these urban environmental stress agents include drought, construction damage, soil compaction, lawnmower & weed whip damage, de-icing salt, vandalism, and air pollution.

Shade trees that are exposed to one or more of these stress agents are much more vulnerable to disease and insect attacks. In fact, many insect pests will only attack a tree that is under severe stress. By planting drought tolerant and/or native species and following proper planting, mulching, watering, and pruning techniques, you will help ensure that your tree remains healthy and vigorous and more able to fight off disease and insects.     

Routinely monitor your trees throughout the growing season. If you notice anything that looks out of the ordinary, contact a licensed, certified arborist. For a full list of licensed, certified artborists in Fort Collins click here.

To learn more about tree disease and insect problems, visit Colorado State University Cooperative Extension to review Trees and Shrubs Facts and Insect Facts. These fact sheets describe disease symptoms, prevention and management techniques. 

Spruce Ips Beetle#

During the summer of 2022, Fort Collins saw a dramatic increase in spruce tree deaths caused by the ips beetle. The spruce ips beetle, Ips hunteri, initially causes mortality in the top of an infested tree, then moves downward, killing the entire tree relatively quickly. 

The spruce ips beetle is an indigenous beetle to Colorado, and Fort Collins and typically attacks trees that are experiencing some form of stress. Dryer soil from reduced irrigation, as well as the abnormally dry, warm, and windy conditions over the last year, have created favorable environments for the beetles to multiply in spruce trees. 

The primary preventative measure tree owners can take to protect trees is to water their spruce trees when the temperature is over 40 degrees. For optimal tree health, the general guideline for watering trees in Fort Collins is to provide 10 gallons of water per diameter inch, every week from May through October, and twice a month if weather allows from November through April. Other preventative spruce treatments can be applied by arborists with the proper State pesticide applicators licenses.

Once a spruce is infested with the ips beetle, there is no effective control for the insect. The wood of infested spruce trees must be carefully disposed of to prevent beetle spread. Infested wood must be immediately chipped, recycled at Ewing Landscape Materials, milled (remove and dispose of all bark), or taken to the landfill for proper disposal after removal. Ips infested wood should not be used for firewood.

For additional questions concerning spruce trees or the ips beetle, please contact the Forestry Division at 970-221-6660 or email forestry@fcgov.com.