Insects attacking forest trees

Insects are part of forest ecosystems. Under certain local conditions, an insect population may erupt and result in mortality of trees in large numbers. Currently, an outbreak of pinyon needle scale and pinyon sawfly, threatening forests in eastern and central Nevada, is reported. The bark beetle is another insect that may harm forests, especially in areas of dense tree growth. To learn more about bark beetles and healthy forests in the Sierra Nevada, walk the Bark Beetle Discovery Trail at Spooner Lake of the Nevada Division of State Parks, east of Lake Tahoe. This short trail is located in the picnic area and features various interpretive sites. An information board introduces the bark beetle as follows:

Bark beetles are always living in forests. They kill clusters of trees, providing dead snags for wildlife habitat, and helping to recycle nutrients from dying trees. They are also food for other insects and woodpeckers. Periodically, bark beetle populations boom when environmental conditions favor the beetles.

References
Jeff DeLong: Pair of bugs threatens Nevada forests. Reno Gazette-Journal, August 10, 2009
USDA Forest Service: Sustaining Alpine and Forest Ecosystems. Forest Insects.