Spruce and fir Needle die off.
What is causing needle die off to our trees? This started one year ago in early fall and killed a fir tree. It spread to one blue spruce and we used Bayer 1&3 as recommended by a local nursery. This seemed to help but this year it has spread. Thanks Andrea
No insects are visible, but note the dark things when photo with hand is enlarged.
From your pictures, it appears you have two different issues with your trees.
The small dwarf Alberta spruce next to the house probably has or had spider mites during the warm period of the summer and fall. Dwarf Alberta spruce is very susceptible. The spider mites are favored by warm and dry conditions. You could trim back, and then spray with an insecticidal soap. Sometimes it helps to wash heavily with a stream of water from the hose. This will be more important next season, as the spider mites have finished their life cycles for the year and will survive as eggs on the lower portions of the plants. Insecticides do not work on mites, as they are more related to spiders.
The Colorado blue spruce may have a needlecast disease caused by a fungus. There again, it is a very specific fungal disease that really only affects spruce, especially blue spruce. The key to control, is pruning out the worst affected lower branches, and then spraying with a fungicide in May. Timing is very important, as the fungicide protects the new needles as they expand in the spring. Spores are released in early May. You need to spray with chlorothalonil (active ingredient) the second week in May, and again 10 days to 2 weeks later.
Hope this helps. Thank you for contacting Cooperative Extension,