According to the Quasar 8.5 SL Product Label: for control of black scale and other forms of scale and insects on ornamentals you would apply 8.5-16.5 fluid ounces of this product per 100 gallons. This comes out to 0.08 to 0.165 oz per gallon for ornamental applications.  If you are planning to do a bark banding treatment for the scale you would apply 12.5-25.3 fluid ounces per gallon of water in mid Spring between bud break and full leaf expansion.