Glenn Kohler

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Silvicultural treatments for management of the
hemlock woolly adelgid in the northeastern U.S.

• Glenn Kohler
• FS 533

Background photo eastern hemlock mortality, Bill
Ciesla
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Hemlock woolly adelgid (HWA), an exotic pest, is
causing widespread mortality to eastern hemlocks
in the eastern U.S.
Connecticut Agricultural Experiment Station
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Following HWA caused mortality

• sites colonized by birches, oaks, and maples
  resulting in a more homogenous hardwood dominated
  landscape

William M. Ciesla, Forest Health Management
International
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• exotic plants may invade the site

Anne Eschtruth, UC Berkeley
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salvage logging?

• 3 silvicultural options following hemlock
  mortality
• do nothing
• cut 20-50 dead hemlock
• cut gt50 dead hemlock

Haliburton Forest, Ontario, Canada
Shaughnessy Forest Products, New Hampshire
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• Salvage logging may cause more environmental
  damage than HWA alone.
• increased nitrification, soil pH, and nitrogen
  leaching
• Pre-emptive salvage is not recommended.
• eliminates possible HWA tolerant seed source.

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Rehabilitation planting

• Replacement conifers
• native pine, spruce, or fir

Single tree/group selection in Red spruce (Picea
rubens), Eastern Hemlock (Tsuga canadensis),
Balsam fir (Abies balsamea) stand on the
Penobscot Experimental Forest. Photo Doug
Maguire, Oregon State University

• Breeding
• HWA resistant Chinese hemlock has been crossed to
  Carolina hemlock

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Regeneration

• Hemlock regeneration site selection
• Factors that increase tolerance to HWA
• soil moisture
• low nitrogen
• cold temperatures

Photo Chris Evans, University of Georgia
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Regeneration cont.

• plant hemlock in small gaps (lt100 m2) to reduce
  competition from hardwoods.
• expose mineral soil if seeding hemlock.
• vegetation control is needed in open areas.

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Take home

• surviving hemlocks can be regenerated on cold,
  wet, low N sites.
• group selection cutting, soil prep., and weed
  control help natural hemlock regeneration.
• protect unique seed sources for the future!

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