Question
I have a 50-60 ft Blue Spruce with scale on the lower branches. I believe that the scale came in a load of wood chips used for mulch.
How can I treat this without using chemical pesticides? Every organic option that I have found refers to discoloration. Is the discoloration permanent?  

Answer
The horticultural oils do tend to turn the color from the bluish to more green. Fertilizer will return this color but it may take a year to show an effect.  Use 30-10-10 fertilizer for the growth and use Aluminum Sulphate to help bring out the blue tinge that they are so famous for and the 30-10-10 will grow them nice and healthy. Use 1 lb per inch of trunk diameter scattered around the tree under the foliage. fertilize now and again in the spring and summer.

I would treat the tree with an insecticide called Bayer Advanced Tree and Shrub Insect Control. This is applied to the soil  around the tree and the roots will carry it to the twigs and foliage and when the scales sucks the plant juices they are killed. Apply in the spring. Here is a web link to this product--check with your local nursery for this.
http://www.bayeradvanced.com/product/Tree-Shrub-Insect-Control/concentrate.html