What's eating my mountain hemlock?

Mountain Hemlock at high elevations faces hemlock woolly adelgid as an emerging threat at lower-elevation margins of its range. Western blackheaded budworm and hemlock looper cause periodic defoliation outbreaks. Bark beetles exploit drought- or snow-press-weakened trees. Deer and elk browse young seedlings in subalpine meadow edges.

White woolly masses on needle bases; needle graying and drop; crown dieback progressing downward; risk increases as climate warming extends pest range to higher elevations Systemic imidacloprid drench for specimen trees at lower elevations; report detections above 1,500 m to state forestry; early intervention is essential at range margins

Rapid complete defoliation by caterpillars; foliage turns rusty brown within weeks; severe outbreaks kill trees in a single season; periodic population cycles in the Pacific Northwest Bt aerial application during outbreak years; populations typically collapse after 2–3 years; single-year defoliation rarely fatal on its own if trees are otherwise healthy

Pitch tubes and boring dust on trunk; sapwood galleries kill cambium; crown reddening and death; attack trees already stressed by drought, root damage, or snow breakage Maintain vigor; remove blow-downs and snow-damaged wood promptly; keep landscape specimens adequately irrigated; avoid wounding bark; no spray recommended in natural forest settings