Forest insect and disease populations and related damage increased throughout Alaskan forests in 1991. Spruce bark beetle populations increased for the third consecutive year. 375,000 acres were impacted in 1991. Hardwood defoliator activity increased for the second year and conifer defoliator populations remain high throughout Alaska. The most significant diseases of Alaskan forests remain yellow cedar decline, wood decay of live trees and hemlock dwarf mistletoe. More than 526,000 acres of cedar decline were mapped in 1991. Spruce needle rust was present at relatively high levels throughout Alaska. Aspen leaf blight was conspicuous for the second consecutive year on portions of the Kenai Peninsula.