How Can I Save My Hemlock Trees?

The Eastern hemlock, or Tsuga canadensis, is a spectacular native evergreen that is common to both wild forests in the northeast and planted landscapes. It is commonly infested by wooly adelgid, an insect that was introduced from Asia to the United States in the first half of the 1900s. The wooly adelgid sucks fluid from the hemlock needles and causes branch die-back, dessication and dropping of needles. Treatments are available. Their effectiveness depends on the extent of damage and disease present.

Horticultural oil
Mask
Sprayer

Instructions

- 1
  Identify the extent of damage and stress to the tree. Are there dead branches? Does the top of the tree look unhealthy or dead? Is the tree wilted? If there is extensive die-back, the tree will not recover because it requires adequate foliage to produce its own food and energy.
- 2
  Observe the tree, looking on the underside of the needles to determine if wooly adelgid is present. Wooly adelgid can be easily spotted by finding the white fluffy egg sacks that resemble tiny pieces of cotton. These white spots are present on the underside of the branches along the twigs where the needles are attached.
- 3
  Purchase a horticultural oil or insecticidal soap from a local nursery or large retail do-it-yourself store if an infestation is present but the tree is not severely stressed. Wear a mask and be sure to follow the directions on the label, taking note of application temperature and any mixing directions. Make sure the oil saturates twigs and needles.
- 4
  Continually monitor the tree. Infestations detected early can be controlled. Make sure the tree is not stressed due to lack of water. A healthier tree is better able to resist damage.

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