This Spring we planted 20 small white spruce that were in containers. The trunk diameter is less than the size of a dime. They looked good for a while but 2 just recently died, the needles became brown almost overnight. When I pulled them out of the ground there were several white bugs in the roots. I don't want the same to happen to the others, we also planted 15 small arbovitae at the same time. What would you recommend I use/do to improve their chances of survival? Thanks!

I suspect that your plants died because of some sort of root injury, drought or transplant shock. The white bugs were most likely feeding on the decaying organic matter from the root decline. When transplanting, avoid wounding roots, plant at the proper depth, and don't let the plants dry out.