Spruce Spider Mite

Scientific Name: Oligonychus ununguis

Spider Mites can be very destructive to evergreens. Although they are very small their populations build up quickly and when extensive damage is observed it may be too late to treat. Fortunately, chemical treatment will also kill both the mite and the eggs, so one treatment is usually all that is needed.

 
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Spruce Spider Mite

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Attacks: Colorado, Norway, white pine, arborvitae, cedars, Douglas fir, hemlock, junipers, larch, and pine.

What you will see:
 
  • Stippling of needles (small yellow or tan dots)
  • Single strands of webbing
  • Shake a branch over a white piece of paper
  • Spider mites are slow moving and green when squished
  • Fast moving red dots are predatory mites

Life cycle:
 
  • Mites overwinter as eggs on bark and needles
  • Eggs hatch in April and May
  • Mites are most active during the cool seasons
  • April and May
  • September and October

Cultural Management of Spruce Spider Mite
 
Cultural practices:
 
  • Use low nitrogen fertilizer
  • Make sure watering is adequate
  • Trees planted too close together are more susceptible
  • Shaded trees are more susceptible
  • Place flowering plants in vicinity - they will provide increased nectar sources for predators

 

Chemical practices:

  • Spider mites are susceptible to topical insecticides. Check with your Arborist for recommended treatment.