That's the same treatment I used for a really bad infestation of Magnolia scale, and the honeydew that came from that huge tree was just disgusting, it was everywhere, made everything under it shiny... shiny evergreen needles, shiny hosta leaves, shiny wrought iron railing (and icky to touch), discolored sidewalk and driveway, couldn't park anywhere near it. I'm also thinking it's honeydew what Strikeo is describing. The sap from some evergreens usually isn't that big of a concern, it's for a short time in the season only.
