Horticultural oil spraying is the most effective spray for your shrubs, ornamentals and evergreens.  The oil not only smothers the insects overwintering in the shrubs, but it kills scale insects that can also damage your valuable landscape.  This spray is done in early spring before the insects hatch.  A second application can be applied in the fall to the hemlock trees.  Lastly, horticultural oil protects your shrubs without applying pesticides.