Timing

• The blue spruce tree's slow growth makes it mostly intolerant to heavy pruning. In order to promote a positive response, the blue spruce must have enough time to repair itself before entering its dormant period. Always complete this tree's pruning during the late winter or early spring months, just before the onset of its growing season. Use sharp, sterile shears to complete the cuts. Wear gloves when pruning to protect your hands from the fairly sharp, mature needles.
  
  

Thinning

• The densely-foliated blue spruce often develops dead areas within the tree's canopy. These dead areas occur when the heavy foliage begins to block the air and sunlight that flows through the tree. To promote healthy cell development throughout the tree's canopy, use sharp, sterile pruning shears to thin the interior branches.
  
  

Old Branches

• Unlike deciduous trees, the blue spruce can take several seasons to defoliate its oldest, lower lying branches. These aging branches often shed its needles and begin to lose its natural bluish-green color. These branches can be removed during the dormant pruning sessions.
  
  

Diseases

• The blue spruce is susceptible to several blight and canker diseases that can cause progressive dieback and stunted growth, when left untreated. Trees with dense foliage are most susceptible because the spores of these infectious diseases thrive in the cool, dark areas of the canopy. Timely thinning of the blue spruce's canopy will greatly reduce the tree's potential for infection. Thinning is especially effective in controlling infection when combined with fungicidal treatments.
  
  

Pests

• Spider mites, scales, aphids, miners and sawflies are the blue spruce's most common pests. These pests take shelter within the tree while feeding on its needles and wood. Severe infestations cause the blue spruce to experience loss of vigor, which can result in dieback. Treat the blue spruce regularly with an approved insecticide to prevent infestations and resulting injury to the tree. Remove dead and damaged areas immediately in order to redirect the tree's energy to more viable areas. Cut damaged branches back to their healthiest points and remove dead branches completely from the tree.