See the article below which recommends controlling the spruce gall adegid by spraying the tree with a product which kills on contact but also is absorbed by the plant tissue for systemic control. The article mentions Orthene and Tempo but there are other similar products available as well. Make sure when selecting an insecticide to read the label to verify it is effective for adelgids and always apply as directed. Monitor your trees and if you see any activity, you can apply the insecticide again in late August or September.
Hope that helps.
Thank you so much! Since writing, we have discovered a couple more spruce trees on our property with the spruce gall. We will be looking for the chemical you recommended.
Jim & Debbie Howie