By Joe Julian, Colorado State University Cooperative Extension, Horticulture
The recent drought has caused an increase in problems associated with the Ips beetle, a small bark beetle that attacks trees that are under some type of environmental stress, have been mechanically damaged, or recently transplanted. Ips is a native insect and common in Colorado forests. Various species of Ips attack spruce and pine in the Rocky Mountain region. The Ips beetle very rarely attacks healthy trees, although when beetle numbers build up, healthy trees may be at risk.
Top dieback on Spruce
There are eleven species of Ips beetle found in Colorado. Each species is host specific, attacking only certain types of spruce or pine. One aspect of the Ips beetle that is different than the mountain pine beetle is several generations of Ips can occur in a season. However, unlike mountain pine beetle, infestation by Ips beetle does not necessarily mean the whole tree will die. The attacked tree, however, is more susceptible to additional attacks and the tree may ultimately die from the series of attacks.
Another factor aiding the increase of Ips beetle populations in Colorado is the creation of freshly cut wood from forest homeowners that experienced fire damage or that are trying to reduce wildfire hazards. Ips beetles will breed in the cut wood and thus population numbers increase. Adult Ips beetle will over winter under the bark of dead and dying trees or in firewood slash or woodcut to clear a fire path.
Adult Ips Beetle tunneling in wood
Controlling Ips beetle requires promotion of vigorous tree growth, something difficult to accomplish in a forested area during drought. Landscaped trees should be given adequate water. Avoid injury to roots by mechanical damage, compaction, etc. Chipping and debarking can eliminate surviving Ips beetle larvae. High valued trees should be preventatively sprayed with either carbaryl (Sevin) or permethrin. Bark beetle applications at the labeled rate should provide at least three months control of Ips beetle. It should be noted that adult Ips beetles have been observed entering trees during warm days as early as late February and on into November. Two preventative insecticide treatments may be needed to protect valuable trees during our current drought period.
Photos: Ron Long, Simon Fraser University, and Colorado Forestry Service
© CSU/Denver County Extension Master Gardener 2010
888 E. Iliff Avenue, Denver, CO 80210
Date last revised: 01/05/2010