Other insects to watch for are bagworms and spider mites. These insects can be extremely damaging to any type of evergreen trees or shrubs. Bagworms are easy to spot in their small brown bags hanging from evergreens. Once you see them, you must act quickly and spray them with Sevin or Malathion. Even when they are dead, the bags will remain there unless they are picked off by hand and destroyed.
Spider mites, on the other hand, are much harder to spot because they are so tiny.
Often, they are not noticed on spruce until damage occurs. Dwarf alberta spruce often seem to be hit the hardest by spider mites. You will start to notice a spot on the spruce turning brown and the needles will begin to drop off. Usually that is Spider mites. To check your spruce, simply take a sheet of white paper and hold it under the brown spot and gently tap the spruce s branches.